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Gasoline (
North American English North American English (NAmE) encompasses the English language as spoken in both the United States and Canada. Because of their related histories and cultures, plus the similarities between the pronunciations (accents), vocabulary, and grammar ...
) or petrol (
Commonwealth English The use of the English language in current and former Member states of the Commonwealth of Nations, countries of Commonwealth of Nations, the Commonwealth was largely inherited from British Empire, British colonisation, with some exceptions. Eng ...
) is a
petrochemical Petrochemicals (sometimes abbreviated as petchems) are the chemical products obtained from petroleum by refining. Some chemical compounds made from petroleum are also obtained from other fossil fuels, such as coal or natural gas, or renewable s ...
product characterized as a transparent, yellowish, and
flammable liquid A flammable liquid is a liquid which can be easily ignited in air at ambient temperatures, i.e. it has a flash point at or below nominal threshold temperatures defined by a number of national and international standards organisations. The Occup ...
normally used as a
fuel A fuel is any material that can be made to react with other substances so that it releases energy as thermal energy or to be used for work (physics), work. The concept was originally applied solely to those materials capable of releasing chem ...
for spark-ignited
internal combustion engine An internal combustion engine (ICE or IC engine) is a heat engine in which the combustion of a fuel occurs with an oxidizer (usually air) in a combustion chamber that is an integral part of the working fluid flow circuit. In an internal comb ...
s. When formulated as a fuel for
engine An engine or motor is a machine designed to convert one or more forms of energy into mechanical energy. Available energy sources include potential energy (e.g. energy of the Earth's gravitational field as exploited in hydroelectric power ge ...
s, gasoline is chemically composed of
organic compound Some chemical authorities define an organic compound as a chemical compound that contains a carbon–hydrogen or carbon–carbon bond; others consider an organic compound to be any chemical compound that contains carbon. For example, carbon-co ...
s derived from the
fractional distillation Fractional distillation is the separation of a mixture into its component parts, or fractions. Chemical compounds are separated by heating them to a temperature at which one or more fractions of the mixture will vaporize. It uses distillation ...
of
petroleum Petroleum, also known as crude oil or simply oil, is a naturally occurring, yellowish-black liquid chemical mixture found in geological formations, consisting mainly of hydrocarbons. The term ''petroleum'' refers both to naturally occurring un ...
and later chemically enhanced with
gasoline additive Gasoline additives may increase gasoline's octane rating, thus allowing the use of higher compression ratios for greater efficiency and power, or act as corrosion inhibitors or lubricants. Other additives include metal deactivators, oxygenates an ...
s. It is a high-volume profitable product produced in crude oil refineries. The ability of a particular gasoline blend to resist premature ignition (which causes knocking and reduces efficiency in
reciprocating engines A reciprocating engine, more often known as a piston engine, is a heat engine that uses one or more reciprocating pistons to convert high temperature and high pressure into a rotating motion. This article describes the common features of all ...
) is measured by its
octane rating An octane rating, or octane number, is a standard measure of a liquid fuel, fuel's ability to withstand Compression ratio, compression in an internal combustion engine without causing engine knocking. The higher the octane number, the more compres ...
.
Tetraethyl lead Tetraethyllead (commonly styled tetraethyl lead), abbreviated TEL, is an organolead compound with the formula Pb( C2H5)4. It was widely used as a fuel additive for much of the 20th century, first being mixed with gasoline beginning in the 192 ...
was once widely used to increase the octane rating but is not used in modern automotive gasoline due to the
health hazard A hazard is a potential source of harm. Substances, events, or circumstances can constitute hazards when their nature would potentially allow them to cause damage to health, life, property, or any other interest of value. The probability of that ...
. Aviation, off-road motor vehicles, and
racing car Auto racing (also known as car racing, motor racing, or automobile racing) is a motorsport involving the racing of automobiles for competition. In North America, the term is commonly used to describe all forms of automobile sport including ...
engines still use leaded gasolines. Other substances are frequently added to gasoline to improve chemical stability and performance characteristics, control corrosion, and provide fuel system cleaning. Gasoline may contain oxygen-containing chemicals such as
ethanol Ethanol (also called ethyl alcohol, grain alcohol, drinking alcohol, or simply alcohol) is an organic compound with the chemical formula . It is an Alcohol (chemistry), alcohol, with its formula also written as , or EtOH, where Et is the ps ...
,
MTBE Methyl ''tert''-butyl ether (MTBE), also known as ''tert''-butyl methyl ether, is an organic compound with a structural formula (CH3)3COCH3. MTBE is a volatile, flammable, and colorless liquid that is sparingly soluble in water. Primarily used as ...
, or
ETBE Ethyl ''tertiary''-butyl ether (ETBE), also known as ethyl ''tert''-butyl ether, is commonly used as an oxygenate gasoline additive in the production of gasoline from crude oil. ETBE offers equal or greater air quality benefits than ethan ...
to improve
combustion Combustion, or burning, is a high-temperature exothermic redox chemical reaction between a fuel (the reductant) and an oxidant, usually atmospheric oxygen, that produces oxidized, often gaseous products, in a mixture termed as smoke. Combustion ...
.


History and etymology

English dictionaries show that the term ''gasoline'' originates from ''
gas Gas is a state of matter that has neither a fixed volume nor a fixed shape and is a compressible fluid. A ''pure gas'' is made up of individual atoms (e.g. a noble gas like neon) or molecules of either a single type of atom ( elements such as ...
'' plus the chemical suffixes '' -ole'' and ''
-ine ''-ine'' is a suffix used in chemistry to denote two kinds of substance. The first is a chemically basic and alkaloidal substance. It was proposed by Joseph Louis Gay-Lussac in an editorial accompanying a paper by Friedrich Sertürner describin ...
''. ''Petrol'' derives from the
Medieval Latin Medieval Latin was the form of Literary Latin used in Roman Catholic Church, Roman Catholic Western Europe during the Middle Ages. It was also the administrative language in the former Western Roman Empire, Roman Provinces of Mauretania, Numidi ...
word ''petroleum'' (L. ''petra'', rock + ''oleum'', oil). Interest in gasoline-like fuels started with the invention of internal combustion engines suitable for use in transportation applications. The so-called
Otto engine The Otto engine is a large stationary single-cylinder internal combustion engine, internal combustion four-stroke engine, designed by the German Nicolaus Otto. It was a low-RPM machine, and only fired every other stroke due to the Otto cycle, a ...
s were developed in Germany during the last quarter of the 19th century. The fuel for these early engines was a relatively volatile
hydrocarbon In organic chemistry, a hydrocarbon is an organic compound consisting entirely of hydrogen and carbon. Hydrocarbons are examples of group 14 hydrides. Hydrocarbons are generally colourless and Hydrophobe, hydrophobic; their odor is usually fain ...
obtained from
coal gas Coal gas is a flammable gaseous fuel made from coal and supplied to the user via a piped distribution system. It is produced when coal is heated strongly in the absence of air. Town gas is a more general term referring to manufactured gaseous ...
. With a
boiling point The boiling point of a substance is the temperature at which the vapor pressure of a liquid equals the pressure surrounding the liquid and the liquid changes into a vapor. The boiling point of a liquid varies depending upon the surrounding envi ...
near ( ''n''-octane boils at ), it was well suited for early
carburetor A carburetor (also spelled carburettor or carburetter) is a device used by a gasoline internal combustion engine to control and mix air and fuel entering the engine. The primary method of adding fuel to the intake air is through the Ventu ...
s (evaporators). The development of a "spray nozzle" carburetor enabled the use of less volatile fuels. Further improvements in engine efficiency were attempted at higher
compression ratio The compression ratio is the ratio between the maximum and minimum volume during the compression stage of the power cycle in a piston or Wankel engine. A fundamental specification for such engines, it can be measured in two different ways. Th ...
s, but early attempts were blocked by the premature explosion of fuel, known as knocking. In 1891, the
Shukhov cracking process The Shukhov cracking process is a thermal cracking process invented by Vladimir Shukhov and Sergei Gavrilov. Origins Shukhov designed and built the first thermal cracking device for the petrochemical industry. His patent (Shukhov cracking proce ...
became the world's first commercial method to break down heavier hydrocarbons in crude oil to increase the percentage of lighter products compared to simple distillation.


Chemical analysis and production

Commercial gasoline as well as other liquid transportation fuels are complex mixtures of hydrocarbons. The performance specification also varies with season, requiring less volatile blends during summer, in order to minimize evaporative losses. Gasoline is produced in
oil refineries An oil refinery or petroleum refinery is an industrial process plant where petroleum (crude oil) is transformed and refined into products such as gasoline (petrol), diesel fuel, asphalt base, fuel oils, heating oil, kerosene, liquefied pet ...
. Roughly of gasoline is derived from a barrel of
crude oil Petroleum, also known as crude oil or simply oil, is a naturally occurring, yellowish-black liquid chemical mixture found in geological formations, consisting mainly of hydrocarbons. The term ''petroleum'' refers both to naturally occurring u ...
. Material separated from crude oil via
distillation Distillation, also classical distillation, is the process of separating the component substances of a liquid mixture of two or more chemically discrete substances; the separation process is realized by way of the selective boiling of the mixt ...
, called virgin or straight-run gasoline, does not meet specifications for modern engines (particularly the
octane rating An octane rating, or octane number, is a standard measure of a liquid fuel, fuel's ability to withstand Compression ratio, compression in an internal combustion engine without causing engine knocking. The higher the octane number, the more compres ...
; see below), but can be pooled to the gasoline blend. The bulk of a typical gasoline consists of a homogeneous mixture of
hydrocarbon In organic chemistry, a hydrocarbon is an organic compound consisting entirely of hydrogen and carbon. Hydrocarbons are examples of group 14 hydrides. Hydrocarbons are generally colourless and Hydrophobe, hydrophobic; their odor is usually fain ...
s with between four and twelve
carbon Carbon () is a chemical element; it has chemical symbol, symbol C and atomic number 6. It is nonmetallic and tetravalence, tetravalent—meaning that its atoms are able to form up to four covalent bonds due to its valence shell exhibiting 4 ...
atoms per molecule (commonly referred to as C4–C12).Werner Dabelstein, Arno Reglitzky, Andrea Schütze and Klaus Reders "Automotive Fuels" in ''Ullmann's Encyclopedia of Industrial Chemistry'' 2007, Wiley-VCH, Weinheim. It is a mixture of paraffins (
alkane In organic chemistry, an alkane, or paraffin (a historical trivial name that also has other meanings), is an acyclic saturated hydrocarbon. In other words, an alkane consists of hydrogen and carbon atoms arranged in a tree structure in whi ...
s), olefins (
alkene In organic chemistry, an alkene, or olefin, is a hydrocarbon containing a carbon–carbon double bond. The double bond may be internal or at the terminal position. Terminal alkenes are also known as Alpha-olefin, α-olefins. The Internationa ...
s), napthenes (
cycloalkane In organic chemistry, the cycloalkanes (also called naphthenes, but distinct from naphthalene) are the ring (chemistry), monocyclic Saturated and unsaturated compounds, saturated hydrocarbons. In other words, a cycloalkane consists only of hydroge ...
s), and
aromatic In organic chemistry, aromaticity is a chemical property describing the way in which a conjugated system, conjugated ring of unsaturated bonds, lone pairs, or empty orbitals exhibits a stabilization stronger than would be expected from conjugati ...
s. The use of the term ''paraffin'' in place of the standard chemical nomenclature ''alkane'' is particular to the oil industry (which relies extensively on jargon). The composition of a gasoline depends upon: * the oil refinery that makes the gasoline, as not all refineries have the same set of processing units; * the
crude oil Petroleum, also known as crude oil or simply oil, is a naturally occurring, yellowish-black liquid chemical mixture found in geological formations, consisting mainly of hydrocarbons. The term ''petroleum'' refers both to naturally occurring u ...
feed used by the refinery; * the grade of gasoline sought (in particular, the octane rating). The various refinery streams blended to make gasoline have different characteristics. Some important streams include the following: * Straight-run gasoline, sometimes referred to as ''
naphtha Naphtha (, recorded as less common or nonstandard in all dictionaries: ) is a flammable liquid hydrocarbon mixture. Generally, it is a fraction of crude oil, but it can also be produced from natural-gas condensates, petroleum distillates, and ...
(and also light straight run naphtha "LSR" and light virgin naphtha "LVN")'', is distilled directly from crude oil. Once the leading source of fuel, naphtha's low octane rating required organometallic fuel additives (primarily
tetraethyllead Tetraethyllead (commonly styled tetraethyl lead), abbreviated TEL, is an organolead compound with the formula lead, Pb(ethyl group, C2H5)4. It was widely used as a fuel additive for much of the 20th century, first being mixed with gasoline begi ...
) prior to their phaseout from the gasoline pool which started in 1975 in the United States. Straight run naphtha is typically low in aromatics (depending on the grade of the crude oil stream) and contains some cycloalkanes (naphthenes) and no olefins (alkenes). Between 0 and 20 percent of this stream is pooled into the finished gasoline because the quantity of this fraction in the crude is less than fuel demand and the fraction's
Research Octane Number An octane rating, or octane number, is a standard measure of a fuel's ability to withstand compression in an internal combustion engine without causing engine knocking. The higher the octane number, the more compression the fuel can withstand befo ...
(RON) is too low. The chemical properties (namely RON and
Reid vapor pressure {{Short description, Measure of the volatility of gasoline and other petroleum products Reid vapor pressure (RVP) is a common measure of the Gasoline#Volatility, volatility of gasoline and other petroleum products. It is defined as the absolute va ...
(RVP)) of the straight-run gasoline can be improved through reforming and
isomerization In chemistry, isomerization or isomerisation is the process in which a molecule, polyatomic ion or molecular fragment is transformed into an isomer with a different chemical structure. Enolization is an example of isomerization, as is tautomer ...
. However, before feeding those units, the naphtha needs to be split into light and heavy naphtha. Straight-run gasoline can also be used as a feedstock for steam-crackers to produce olefins. * Reformate, produced from straight run gasoline in a
catalytic reformer Catalytic reforming is a chemical process used to convert naphthas from crude oil into liquid products called reformates, which are premium "blending stocks" for high-octane gasoline. The process converts low-octane linear hydrocarbons (paraffins ...
, has a high octane rating with high aromatic content and relatively low olefin content. Most of the
benzene Benzene is an Organic compound, organic chemical compound with the Chemical formula#Molecular formula, molecular formula C6H6. The benzene molecule is composed of six carbon atoms joined in a planar hexagonal Ring (chemistry), ring with one hyd ...
,
toluene Toluene (), also known as toluol (), is a substituted aromatic hydrocarbon with the chemical formula , often abbreviated as , where Ph stands for the phenyl group. It is a colorless, water Water is an inorganic compound with the c ...
, and
xylene In organic chemistry, xylene or xylol (; IUPAC name: dimethylbenzene) are any of three organic compounds with the formula . They are derived from the substitution of two hydrogen atoms with methyl groups in a benzene ring; which hydrogens are su ...
(the so-called BTX hydrocarbons) are more valuable as chemical feedstocks and are thus removed to some extent. Also the BTX content is regulated. * Catalytic cracked gasoline, or catalytic cracked
naphtha Naphtha (, recorded as less common or nonstandard in all dictionaries: ) is a flammable liquid hydrocarbon mixture. Generally, it is a fraction of crude oil, but it can also be produced from natural-gas condensates, petroleum distillates, and ...
, produced with a catalytic cracker, has a moderate octane rating, high olefin content, and moderate aromatic content. * Hydrocrackate (heavy, mid, and light), produced with a
hydrocracker In petrochemistry, petroleum geology and organic chemistry, cracking is the process whereby complex organic molecules such as kerogens or long-chain hydrocarbons are broken down into simpler molecules such as light hydrocarbons, by the breaking ...
, has a medium to low octane rating and moderate aromatic levels. * Alkylate is produced in an
alkylation Alkylation is a chemical reaction that entails transfer of an alkyl group. The alkyl group may be transferred as an alkyl carbocation, a free radical, a carbanion, or a carbene (or their equivalents). Alkylating agents are reagents for effecting al ...
unit, using
isobutane Isobutane, also known as ''i''-butane, 2-methylpropane or methylpropane, is a chemical compound with molecular formula HC(CH3)3. It is an isomer of butane. Isobutane is a colorless, odorless gas. It is the simplest alkane with a tertiary carbon a ...
and C3-/C4-olefins as feedstocks. Finished alkylate contains no aromatics or olefins and has a high MON (
Motor Octane Number An octane rating, or octane number, is a standard measure of a fuel's ability to withstand compression in an internal combustion engine without causing engine knocking. The higher the octane number, the more compression the fuel can withstand bef ...
) Alkylate was used during world war 2 in
aviation fuel Aviation fuels are either petroleum-based or blends of petroleum and synthetic fuels, used to power aircraft. They have more stringent requirements than fuels used for ground applications, such as heating and road transport, and they contain add ...
. Since the late 1980s it is sold as a specialty fuel for (handheld) gardening and forestry tools with a combustion engine. * Isomerate is obtained by isomerizing low-octane straight-run gasoline into iso-paraffins (non-chain alkanes, such as
isooctane 2,2,4-Trimethylpentane, also known as isooctane or iso-octane, is an organic compound with the formula (CH3)3CCH2CH(CH3)2. It is one of several isomers of octane (C8H18). This particular isomer is the standard 100 point on the octane rating scal ...
). Isomerate has a medium RON and MON, but no aromatics or olefins. * Butane is usually blended in the gasoline pool, although the quantity of this stream is limited by the RVP specification. *
Oxygenate In the liquid fuel industry, oxygenates are hydrocarbon-derived fuel additives containing at least one oxygen atom to promote complete combustion. Absent oxygenates, fuel combustion is usually incomplete, and the exhaust stream pollutes the air ...
s (more specifically
alcohols In chemistry, an alcohol (), is a type of organic compound that carries at least one hydroxyl () functional group bound to a Saturated and unsaturated compounds, saturated carbon atom. Alcohols range from the simple, like methanol and ethanol ...
and
ester In chemistry, an ester is a compound derived from an acid (either organic or inorganic) in which the hydrogen atom (H) of at least one acidic hydroxyl group () of that acid is replaced by an organyl group (R). These compounds contain a distin ...
s) are mostly blended into the pool in the US as
ethanol Ethanol (also called ethyl alcohol, grain alcohol, drinking alcohol, or simply alcohol) is an organic compound with the chemical formula . It is an Alcohol (chemistry), alcohol, with its formula also written as , or EtOH, where Et is the ps ...
. In Europe and other countries, the blends can contain
ethanol Ethanol (also called ethyl alcohol, grain alcohol, drinking alcohol, or simply alcohol) is an organic compound with the chemical formula . It is an Alcohol (chemistry), alcohol, with its formula also written as , or EtOH, where Et is the ps ...
in addition to Methyl tertiary-butyl ether (MTBE) and
Ethyl tert-butyl ether Ethyl ''tertiary''-butyl ether (ETBE), also known as ethyl ''tert''-butyl ether, is commonly used as an oxygenate gasoline additive in the production of gasoline from crude oil. ETBE offers equal or greater air quality benefits than eth ...
(ETBE). MTBE in the United States was banned by most states in the early to mid 2000s. A few countries still allow
methanol Methanol (also called methyl alcohol and wood spirit, amongst other names) is an organic chemical compound and the simplest aliphatic Alcohol (chemistry), alcohol, with the chemical formula (a methyl group linked to a hydroxyl group, often ab ...
as well to be blended directly into gasoline, especially in China. More about oxygenates and blending is covered further in this article. The terms above are the jargon used in the oil industry, and the terminology varies. Currently, many countries set limits on gasoline
aromatic In organic chemistry, aromaticity is a chemical property describing the way in which a conjugated system, conjugated ring of unsaturated bonds, lone pairs, or empty orbitals exhibits a stabilization stronger than would be expected from conjugati ...
s in general, benzene in particular, and olefin (alkene) content. Such regulations have led to an increasing preference for alkane isomers, such as isomerate or alkylate, as their octane rating is higher than n-alkanes. In the European Union, the benzene limit is set at one percent by volume for all grades of automotive gasoline. This is usually achieved by avoiding feeding C6, in particular
cyclohexane Cyclohexane is a cycloalkane with the molecular formula . Cyclohexane is non-polar. Cyclohexane is a colourless, flammable liquid with a distinctive detergent-like odor, reminiscent of cleaning products (in which it is sometimes used). Cyclohexan ...
, to the reformer unit, where it would be converted to benzene. Therefore, only (desulfurized) heavy virgin naphtha (HVN) is fed to the reformer unit Gasoline can also contain other
organic compound Some chemical authorities define an organic compound as a chemical compound that contains a carbon–hydrogen or carbon–carbon bond; others consider an organic compound to be any chemical compound that contains carbon. For example, carbon-co ...
s, such as organic ethers (deliberately added), plus small levels of contaminants, in particular
organosulfur Organosulfur chemistry is the study of the properties and synthesis of organosulfur compounds, which are organic compounds that contain sulfur. They are often associated with foul odors, but many of the sweetest compounds known are organosulfur der ...
compounds (which are usually removed at the refinery). On average, U.S. petroleum refineries produce about 19 to 20 gallons of gasoline, 11 to 13 gallons of distillate fuel
diesel fuel Diesel fuel, also called diesel oil, heavy oil (historically) or simply diesel, is any liquid fuel specifically designed for use in a diesel engine, a type of internal combustion engine in which fuel ignition takes place without a spark as a re ...
and 3 to 4 gallons of
jet fuel Jet fuel or aviation turbine fuel (ATF, also abbreviated avtur) is a type of aviation fuel designed for use in aircraft powered by Gas turbine, gas-turbine engines. It is colorless to straw-colored in appearance. The most commonly used fuels for ...
from each
barrel A barrel or cask is a hollow cylindrical container with a bulging center, longer than it is wide. They are traditionally made of wooden stave (wood), staves and bound by wooden or metal hoops. The word vat is often used for large containers ...
of crude oil. The product ratio depends upon the processing in an
oil refinery An oil refinery or petroleum refinery is an industrial processes, industrial process Factory, plant where petroleum (crude oil) is transformed and refining, refined into products such as gasoline (petrol), diesel fuel, Bitumen, asphalt base, ...
and the
crude oil assay A crude oil assay is the chemical evaluation of crude oil feedstocks by petroleum testing laboratories. Each crude oil type has unique molecular and chemical characteristics. No two crude oil types are identical and there are crucial differences ...
.


Physical properties


Density

The
specific gravity Relative density, also called specific gravity, is a dimensionless quantity defined as the ratio of the density (mass of a unit volume) of a substance to the density of a given reference material. Specific gravity for solids and liquids is nea ...
of gasoline ranges from 0.71 to 0.77, with higher densities having a greater volume fraction of aromatics. Finished marketable gasoline is traded (in Europe) with a standard reference of , (7,5668 lb/ imp gal) its price is escalated or de-escalated according to its actual density. Because of its low density, gasoline floats on water, and therefore water cannot generally be used to extinguish a gasoline fire unless applied in a fine mist.


Stability

Quality gasoline should be
stable A stable is a building in which working animals are kept, especially horses or oxen. The building is usually divided into stalls, and may include storage for equipment and feed. Styles There are many different types of stables in use tod ...
for six months if stored properly, but can degrade over time. Gasoline stored for a year will most likely be able to be burned in an internal combustion engine without too much trouble. Gasoline should ideally be stored in an airtight container (to prevent
oxidation Redox ( , , reduction–oxidation or oxidation–reduction) is a type of chemical reaction in which the oxidation states of the reactants change. Oxidation is the loss of electrons or an increase in the oxidation state, while reduction is ...
or water vapor mixing in with the gas) that can withstand the
vapor pressure Vapor pressure or equilibrium vapor pressure is the pressure exerted by a vapor in thermodynamic equilibrium with its condensed phases (solid or liquid) at a given temperature in a closed system. The equilibrium vapor pressure is an indicat ...
of the gasoline without venting (to prevent the loss of the more volatile fractions) at a stable cool temperature (to reduce the excess pressure from liquid expansion and to reduce the rate of any decomposition reactions). When gasoline is not stored correctly, gums and solids may result, which can corrode system components and accumulate on wet surfaces, resulting in a condition called "stale fuel". Gasoline containing ethanol is especially subject to absorbing atmospheric moisture, then forming gums, solids, or two phases (a hydrocarbon phase floating on top of a water-alcohol phase). The presence of these degradation products in the fuel tank or fuel lines plus a carburetor or fuel injection components makes it harder to start the engine or causes reduced engine performance On resumption of regular engine use, the buildup may or may not be eventually cleaned out by the flow of fresh gasoline. The addition of a fuel stabilizer to gasoline can extend the life of fuel that is not or cannot be stored properly, though removal of all fuel from a fuel system is the only real solution to the problem of long-term storage of an engine or a machine or vehicle. Typical fuel stabilizers are proprietary mixtures containing
mineral spirits White spirit (AU, UK and Ireland)Primarily in the United Kingdom and Australia. In New Zealand "white spirit" can also refer to Coleman fuel ( white gas). or mineral spirits (US, Canada), also known as mineral turpentine (AU/NZ/ZA), turpentine s ...
,
isopropyl alcohol Isopropyl alcohol (IUPAC name propan-2-ol and also called isopropanol or 2-propanol) is a colorless, flammable, organic compound with a pungent alcoholic odor. Isopropyl alcohol, an organic polar molecule, is miscible in water, ethanol, an ...
, 1,2,4-trimethylbenzene or other additives. Fuel stabilizers are commonly used for small engines, such as lawnmower and tractor engines, especially when their use is sporadic or seasonal (little to no use for one or more seasons of the year). Users have been advised to keep gasoline containers more than half full and properly capped to reduce air exposure, to avoid storage at high temperatures, to run an engine for ten minutes to circulate the stabilizer through all components prior to storage, and to run the engine at intervals to purge stale fuel from the carburetor. Gasoline stability requirements are set by the standard
ASTM ASTM International, formerly known as American Society for Testing and Materials, is a standards organization that develops and publishes voluntary consensus technical international standards for a wide range of materials, products, systems and s ...
D4814. This standard describes the various characteristics and requirements of automotive fuels for use over a wide range of operating conditions in ground vehicles equipped with spark-ignition engines.


Combustion energy content

A gasoline-fueled internal combustion engine obtains energy from the
combustion Combustion, or burning, is a high-temperature exothermic redox chemical reaction between a fuel (the reductant) and an oxidant, usually atmospheric oxygen, that produces oxidized, often gaseous products, in a mixture termed as smoke. Combustion ...
of gasoline's various hydrocarbons with
oxygen Oxygen is a chemical element; it has chemical symbol, symbol O and atomic number 8. It is a member of the chalcogen group (periodic table), group in the periodic table, a highly reactivity (chemistry), reactive nonmetal (chemistry), non ...
from the ambient air, yielding
carbon dioxide Carbon dioxide is a chemical compound with the chemical formula . It is made up of molecules that each have one carbon atom covalent bond, covalently double bonded to two oxygen atoms. It is found in a gas state at room temperature and at norma ...
and
water Water is an inorganic compound with the chemical formula . It is a transparent, tasteless, odorless, and Color of water, nearly colorless chemical substance. It is the main constituent of Earth's hydrosphere and the fluids of all known liv ...
as exhaust. The combustion of
octane Octane is a hydrocarbon and also an alkane with the chemical formula C8H18, and the condensed structural formula CH3(CH2)6CH3. Octane has many structural isomers that differ by the location of branching in the carbon chain. One of these isomers ...
, a representative species, performs the chemical reaction: : By weight, combustion of gasoline releases about or by volume , quoting the
lower heating value The heating value (or energy value or calorific value) of a substance, usually a fuel or food (see food energy), is the amount of heat released during the combustion of a specified amount of it. The ''calorific value'' is the total energy release ...
. Gasoline blends differ, and therefore actual energy content varies according to the season and producer by up to 1.75 percent more or less than the average. On average, about of gasoline are available from a barrel of crude oil (about 46 percent by volume), varying with the quality of the crude and the grade of the gasoline. The remainder is products ranging from tar to
naphtha Naphtha (, recorded as less common or nonstandard in all dictionaries: ) is a flammable liquid hydrocarbon mixture. Generally, it is a fraction of crude oil, but it can also be produced from natural-gas condensates, petroleum distillates, and ...
. A high-octane-rated fuel, such as
liquefied petroleum gas Liquefied petroleum gas, also referred to as liquid petroleum gas (LPG or LP gas), is a fuel gas which contains a flammable mixture of hydrocarbon gases, specifically propane, Butane, ''n''-butane and isobutane. It can also contain some ...
(LPG), has an overall lower power output at the typical 10:1
compression ratio The compression ratio is the ratio between the maximum and minimum volume during the compression stage of the power cycle in a piston or Wankel engine. A fundamental specification for such engines, it can be measured in two different ways. Th ...
of an engine design optimized for gasoline fuel. An engine tuned for LPG fuel via higher compression ratios (typically 12:1) improves the power output. This is because higher-octane fuels allow for a higher compression ratio without knocking, resulting in a higher cylinder temperature, which improves
efficiency Efficiency is the often measurable ability to avoid making mistakes or wasting materials, energy, efforts, money, and time while performing a task. In a more general sense, it is the ability to do things well, successfully, and without waste. ...
. Also, increased mechanical efficiency is created by a higher compression ratio through the concomitant higher expansion ratio on the power stroke, which is by far the greater effect. The higher expansion ratio extracts more work from the high-pressure gas created by the combustion process. An
Atkinson cycle The Atkinson-cycle engine is a type of internal combustion engine invented by James Atkinson (inventor), James Atkinson in 1882. The Atkinson cycle is designed to provide Energy conversion efficiency, efficiency at the expense of power density. ...
engine uses the timing of the valve events to produce the benefits of a high expansion ratio without the disadvantages, chiefly detonation, of a high compression ratio. A high expansion ratio is also one of the two key reasons for the efficiency of
diesel engine The diesel engine, named after the German engineer Rudolf Diesel, is an internal combustion engine in which Combustion, ignition of diesel fuel is caused by the elevated temperature of the air in the cylinder due to Mechanics, mechanical Compr ...
s, along with the elimination of pumping losses due to throttling of the intake airflow. The lower energy content of LPG by liquid volume in comparison to gasoline is due mainly to its lower density. This lower density is a property of the lower
molecular weight A molecule is a group of two or more atoms that are held together by Force, attractive forces known as chemical bonds; depending on context, the term may or may not include ions that satisfy this criterion. In quantum physics, organic chemi ...
of
propane Propane () is a three-carbon chain alkane with the molecular formula . It is a gas at standard temperature and pressure, but becomes liquid when compressed for transportation and storage. A by-product of natural gas processing and petroleum ref ...
(LPG's chief component) compared to gasoline's blend of various hydrocarbon compounds with heavier molecular weights than propane. Conversely, LPG's energy content by weight is higher than gasoline's due to a higher
hydrogen Hydrogen is a chemical element; it has chemical symbol, symbol H and atomic number 1. It is the lightest and abundance of the chemical elements, most abundant chemical element in the universe, constituting about 75% of all baryon, normal matter ...
-to-
carbon Carbon () is a chemical element; it has chemical symbol, symbol C and atomic number 6. It is nonmetallic and tetravalence, tetravalent—meaning that its atoms are able to form up to four covalent bonds due to its valence shell exhibiting 4 ...
ratio. Molecular weights of the species in the representative octane combustion are 114, 32, 44, and 18 for C8H18, O2, CO2, and H2O, respectively; therefore of fuel reacts with of oxygen to produce of carbon dioxide and of water.


Octane rating

Spark-ignition engine A spark-ignition engine (SI engine) is an internal combustion engine, generally a petrol engine, where the combustion process of the air-fuel mixture is ignited by a spark from a spark plug. This is in contrast to compression-ignition engines, ty ...
s are designed to burn gasoline in a controlled process called
deflagration Deflagration (Lat: ''de + flagrare'', 'to burn down') is subsonic combustion in which a pre-mixed flame propagates through an explosive or a mixture of fuel and oxidizer. Deflagrations in high and low explosives or fuel–oxidizer mixtures ma ...
. However, the unburned mixture may autoignite by pressure and heat alone, rather than igniting from the
spark plug A spark plug (sometimes, in British English, a sparking plug, and, colloquially, a plug) is a device for delivering electric current from an ignition system to the combustion chamber of a spark-ignition engine to ignite the compressed fuel/air ...
at exactly the right time, causing a rapid pressure rise that can damage the engine. This is often referred to as
engine knocking In spark-ignition internal combustion engines, knocking (also knock, detonation, spark knock, pinging or pinking) occurs when combustion of some of the air/fuel mixture in the cylinder does not result from propagation of the flame front ignite ...
or end-gas knock. Knocking can be reduced by increasing the gasoline's resistance to
autoignition The autoignition temperature or self-ignition temperature, often called spontaneous ignition temperature or minimum ignition temperature (or shortly ignition temperature) and formerly also known as kindling point, of a substance is the lowest temp ...
, which is expressed by its octane rating. A detailed analysis further explores the conditions where premium fuel provides actual performance benefits versus when it is unnecessary. Octane rating is measured relative to a mixture of
2,2,4-trimethylpentane 2,2,4-Trimethylpentane, also known as isooctane or iso-octane, is an organic compound with the formula (CH3)3CCH2CH(CH3)2. It is one of several isomers of octane (C8H18). This particular isomer is the standard 100 point on the octane rating scale ...
(an
isomer In chemistry, isomers are molecules or polyatomic ions with identical molecular formula – that is, the same number of atoms of each element (chemistry), element – but distinct arrangements of atoms in space. ''Isomerism'' refers to the exi ...
of
octane Octane is a hydrocarbon and also an alkane with the chemical formula C8H18, and the condensed structural formula CH3(CH2)6CH3. Octane has many structural isomers that differ by the location of branching in the carbon chain. One of these isomers ...
) and n-
heptane Heptane or ''n''-heptane is the straight-chain alkane with the chemical formula H3C(CH2)5CH3 or C7H16. When used as a test fuel component in anti-knock test engines, a 100% heptane fuel is the zero point of the octane rating scale (the 100 poi ...
. There are different conventions for expressing octane ratings, so the same physical fuel may have several different octane ratings based on the measure used. One of the best known is the research octane number (RON). The octane rating of typical commercially available gasoline varies by country. In
Finland Finland, officially the Republic of Finland, is a Nordic country in Northern Europe. It borders Sweden to the northwest, Norway to the north, and Russia to the east, with the Gulf of Bothnia to the west and the Gulf of Finland to the south, ...
,
Sweden Sweden, formally the Kingdom of Sweden, is a Nordic countries, Nordic country located on the Scandinavian Peninsula in Northern Europe. It borders Norway to the west and north, and Finland to the east. At , Sweden is the largest Nordic count ...
, and
Norway Norway, officially the Kingdom of Norway, is a Nordic countries, Nordic country located on the Scandinavian Peninsula in Northern Europe. The remote Arctic island of Jan Mayen and the archipelago of Svalbard also form part of the Kingdom of ...
, 95 RON is the standard for regular unleaded gasoline and 98 RON is also available as a more expensive option. In the United Kingdom, over 95 percent of gasoline sold has 95 RON and is marketed as Unleaded or Premium Unleaded. Super Unleaded, with 97/98 RON and branded high-performance fuels (e.g., Shell V-Power, BP Ultimate) with 99 RON make up the balance. Gasoline with 102 RON may rarely be available for racing purposes. In the U.S., octane ratings in unleaded fuels vary between 85 and 87 AKI (91–92 RON) for regular, 89–90 AKI (94–95 RON) for mid-grade (equivalent to European regular), up to 90–94 AKI (95–99 RON) for premium (European premium). As South Africa's largest city,
Johannesburg Johannesburg ( , , ; Zulu language, Zulu and Xhosa language, Xhosa: eGoli ) (colloquially known as Jozi, Joburg, Jo'burg or "The City of Gold") is the most populous city in South Africa. With 5,538,596 people in the City of Johannesburg alon ...
, is located on the
Highveld The Highveld (Afrikaans: ''Hoëveld,'' , ) is the portion of the South African inland plateau which has an altitude above roughly , but below , thus excluding the Lesotho mountain regions to the south-east of the Highveld. It is home to some of t ...
at above sea level, the
Automobile Association of South Africa The Automobile Association of South Africa, often abbreviated AA is an automobile association that has been operating in South Africa since 1930. It is a non-profit organisation providing services to its members such as roadside assistance, tech ...
recommends 95-octane gasoline at low altitude and 93-octane for use in Johannesburg because "The higher the altitude the lower the air pressure, and the lower the need for a high octane fuel as there is no real performance gain". Octane rating became important as the military sought higher output for
aircraft engine An aircraft engine, often referred to as an aero engine, is the power component of an aircraft propulsion system. Aircraft using power components are referred to as powered flight. Most aircraft engines are either piston engines or gas turbin ...
s in the late 1920s and the 1940s. A higher octane rating allows a higher
compression ratio The compression ratio is the ratio between the maximum and minimum volume during the compression stage of the power cycle in a piston or Wankel engine. A fundamental specification for such engines, it can be measured in two different ways. Th ...
or
supercharger In an internal combustion engine, a supercharger compresses the intake gas, forcing more air into the engine in order to produce more power for a given displacement (engine), displacement. It is a form of forced induction that is mechanically ...
boost, and thus higher temperatures and pressures, which translate to higher power output. Some scientists even predicted that a nation with a good supply of high-octane gasoline would have the advantage in air power. In 1943, the
Rolls-Royce Merlin The Rolls-Royce Merlin is a British Coolant#Liquids, liquid-cooled V12 engine, V-12 Reciprocating engine, piston aero engine of 27-litre (1,650 cu in) Engine displacement, capacity. Rolls-Royce Limited, Rolls-Royce designed the engine an ...
aero engine produced using 100 RON fuel from a modest displacement. By the time of
Operation Overlord Operation Overlord was the codename for the Battle of Normandy, the Allies of World War II, Allied operation that launched the successful liberation of German-occupied Western Front (World War II), Western Europe during World War II. The ope ...
, both the RAF and USAAF were conducting some operations in Europe using 150 RON fuel (100/150
avgas Avgas (aviation gasoline, also known as aviation spirit in the United Kingdom, UK) is an aviation fuel used in aircraft with spark-ignited internal combustion engines. ''Avgas'' is distinguished from conventional gasoline (petrol) used in moto ...
), obtained by adding 2.5 percent
aniline Aniline (From , meaning ' indigo shrub', and ''-ine'' indicating a derived substance) is an organic compound with the formula . Consisting of a phenyl group () attached to an amino group (), aniline is the simplest aromatic amine. It is an in ...
to 100-octane avgas. By this time, the Rolls-Royce Merlin 66 was developing using this fuel.


Additives


Antiknock additives


Tetraethyl lead

Gasoline, when used in high-
compression Compression may refer to: Physical science *Compression (physics), size reduction due to forces *Compression member, a structural element such as a column *Compressibility, susceptibility to compression * Gas compression *Compression ratio, of a ...
internal combustion engines, tends to auto-ignite or "detonate" causing damaging
engine knocking In spark-ignition internal combustion engines, knocking (also knock, detonation, spark knock, pinging or pinking) occurs when combustion of some of the air/fuel mixture in the cylinder does not result from propagation of the flame front ignite ...
(also called "pinging" or "pinking"). To address this problem,
tetraethyl lead Tetraethyllead (commonly styled tetraethyl lead), abbreviated TEL, is an organolead compound with the formula Pb( C2H5)4. It was widely used as a fuel additive for much of the 20th century, first being mixed with gasoline beginning in the 192 ...
(TEL) was widely adopted as an additive for gasoline in the 1920s. With a growing awareness of the seriousness of the extent of environmental and health damage caused by lead compounds, however, and the incompatibility of lead with
catalytic converter A catalytic converter part is an vehicle emissions control, exhaust emission control device which converts toxic gases and pollutants in exhaust gas from an internal combustion engine into less-toxic pollutants by catalysis, catalyzing a redox ...
s, governments began to mandate reductions in gasoline lead. In the U.S., the
Environmental Protection Agency Environmental Protection Agency may refer to the following government organizations: * Environmental Protection Agency (Queensland), Australia * Environmental Protection Agency (Ghana) * Environmental Protection Agency (Ireland) * Environmenta ...
issued regulations to reduce the lead content of leaded gasoline over a series of annual phases, scheduled to begin in 1973 but delayed by court appeals until 1976. By 1995, leaded fuel accounted for only 0.6 percent of total gasoline sales and under () of lead per year. From 1 January 1996, the U.S. Clean Air Act banned the sale of leaded fuel for use in on-road vehicles in the U.S. The use of TEL also necessitated other additives, such as
dibromoethane Dibromoethane can refer to either of two isomeric organobromides with the molecular formula C2H4Br2: * 1,1-Dibromoethane (ethylidene dibromide) * 1,2-Dibromoethane 1,2-Dibromoethane, also known as ethylene dibromide (EDB), is an organobromine com ...
. European countries began replacing lead-containing additives by the end of the 1980s, and by the end of the 1990s, leaded gasoline was banned within the entire European Union with an exception for Avgas 100LL for
general aviation General aviation (GA) is defined by the International Civil Aviation Organization (ICAO) as all civil aviation aircraft operations except for commercial air transport or aerial work, which is defined as specialized aviation services for other ...
. The UAE started to switch to unleaded in the early 2000s. Reduction in the average lead content of human blood may be a major cause for falling violent crime rates around the world including South Africa. A study found a correlation between leaded gasoline usage and violent crime (see Lead–crime hypothesis). Other studies found no correlation. In August 2021, the
UN Environment Programme The United Nations Environment Programme (UNEP) is responsible for coordinating responses to environmental issues within the United Nations system. It was established by Maurice Strong, its first director, after the United Nations Conference on t ...
announced that leaded gasoline had been eradicated worldwide, with
Algeria Algeria, officially the People's Democratic Republic of Algeria, is a country in the Maghreb region of North Africa. It is bordered to Algeria–Tunisia border, the northeast by Tunisia; to Algeria–Libya border, the east by Libya; to Alger ...
being the last country to deplete its reserves.
UN Secretary-General The secretary-general of the United Nations (UNSG or UNSECGEN) is the chief administrative officer of the United Nations and head of the United Nations Secretariat, one of the United Nations System#Six principal organs, six principal organs of ...
António Guterres António Manuel de Oliveira Guterres (born 30 April 1949) is a Portuguese politician and diplomat who is serving as the ninth and current secretary-general of the United Nations since 2017. A member of the Socialist Party (Portugal), ...
called the eradication of leaded petrol an "international success story". He also added: "Ending the use of leaded petrol will prevent more than one million premature deaths each year from heart disease, strokes and cancer, and it will protect children whose IQs are damaged by exposure to lead".
Greenpeace Greenpeace is an independent global campaigning network, founded in Canada in 1971 by a group of Environmental movement, environmental activists. Greenpeace states its goal is to "ensure the ability of the Earth to nurture life in all its biod ...
called the announcement "the end of one toxic era". However, leaded gasoline continues to be used in aeronautic, auto racing, and off-road applications. The use of leaded additives is still permitted worldwide for the formulation of some grades of
aviation gasoline Avgas (aviation gasoline, also known as aviation spirit in the UK) is an aviation fuel used in aircraft with spark-ignited internal combustion engines. ''Avgas'' is distinguished from conventional gasoline (petrol) used in motor vehicles, wh ...
such as
100LL Avgas (aviation gasoline, also known as aviation spirit in the UK) is an aviation fuel used in aircraft with spark-ignited internal combustion engines. ''Avgas'' is distinguished from conventional gasoline (petrol) used in motor vehicles, whi ...
, because the required octane rating is difficult to reach without the use of leaded additives. Different additives have replaced lead compounds. The most popular additives include
aromatic hydrocarbon Aromatic compounds or arenes are organic compounds "with a chemistry typified by benzene" and "cyclically conjugated." The word "aromatic" originates from the past grouping of molecules based on odor, before their general chemical properties were ...
s,
ether In organic chemistry, ethers are a class of compounds that contain an ether group, a single oxygen atom bonded to two separate carbon atoms, each part of an organyl group (e.g., alkyl or aryl). They have the general formula , where R and R ...
s (
MTBE Methyl ''tert''-butyl ether (MTBE), also known as ''tert''-butyl methyl ether, is an organic compound with a structural formula (CH3)3COCH3. MTBE is a volatile, flammable, and colorless liquid that is sparingly soluble in water. Primarily used as ...
and
ETBE Ethyl ''tertiary''-butyl ether (ETBE), also known as ethyl ''tert''-butyl ether, is commonly used as an oxygenate gasoline additive in the production of gasoline from crude oil. ETBE offers equal or greater air quality benefits than ethan ...
), and
alcohols In chemistry, an alcohol (), is a type of organic compound that carries at least one hydroxyl () functional group bound to a Saturated and unsaturated compounds, saturated carbon atom. Alcohols range from the simple, like methanol and ethanol ...
, most commonly
ethanol Ethanol (also called ethyl alcohol, grain alcohol, drinking alcohol, or simply alcohol) is an organic compound with the chemical formula . It is an Alcohol (chemistry), alcohol, with its formula also written as , or EtOH, where Et is the ps ...
.


Lead replacement petrol

Lead replacement petrol (LRP) was developed for vehicles designed to run on leaded fuels and incompatible with unleaded fuels. Rather than tetraethyllead, it contains other metals such as
potassium Potassium is a chemical element; it has Symbol (chemistry), symbol K (from Neo-Latin ) and atomic number19. It is a silvery white metal that is soft enough to easily cut with a knife. Potassium metal reacts rapidly with atmospheric oxygen to ...
compounds or
methylcyclopentadienyl manganese tricarbonyl Methylcyclopentadienyl manganese tricarbonyl (MMT or MCMT) is an organomanganese compound with the formula (C5H4CH3)Mn(CO)3. Initially marketed as a supplement for use in leaded gasoline, MMT was later used in unleaded gasoline to increase the oc ...
(MMT); these are purported to buffer soft exhaust valves and seats so that they do not suffer recession due to the use of unleaded fuel. LRP was marketed during and after the phaseout of leaded motor fuels in the United Kingdom,
Australia Australia, officially the Commonwealth of Australia, is a country comprising mainland Australia, the mainland of the Australia (continent), Australian continent, the island of Tasmania and list of islands of Australia, numerous smaller isl ...
,
South Africa South Africa, officially the Republic of South Africa (RSA), is the Southern Africa, southernmost country in Africa. Its Provinces of South Africa, nine provinces are bounded to the south by of coastline that stretches along the Atlantic O ...
, and some other countries. Consumer confusion led to a widespread mistaken preference for LRP rather than unleaded, and LRP was phased out 8 to 10 years after the introduction of unleaded. Leaded gasoline was withdrawn from sale in Britain after 31 December 1999, seven years after
EEC The European Economic Community (EEC) was a regional organisation created by the Treaty of Rome of 1957,Today the largely rewritten treaty continues in force as the ''Treaty on the functioning of the European Union'', as renamed by the Lisbo ...
regulations signaled the end of production for cars using leaded gasoline in member states. At this stage, a large percentage of cars from the 1980s and early 1990s which ran on leaded gasoline were still in use, along with cars that could run on unleaded fuel. However, the declining number of such cars on British roads saw many gasoline stations withdrawing LRP from sale by 2003.


MMT

Methylcyclopentadienyl manganese tricarbonyl Methylcyclopentadienyl manganese tricarbonyl (MMT or MCMT) is an organomanganese compound with the formula (C5H4CH3)Mn(CO)3. Initially marketed as a supplement for use in leaded gasoline, MMT was later used in unleaded gasoline to increase the oc ...
(MMT) is used in Canada and the U.S. to boost octane rating. Its use in the U.S. has been restricted by regulations, although it is currently allowed. Its use in the European Union is restricted by Article 8a of the Fuel Quality Directive following its testing under the Protocol for the evaluation of effects of metallic fuel-additives on the emissions performance of vehicles.


Fuel stabilizers (antioxidants and metal deactivators)

Gummy, sticky resin deposits result from
oxidative Redox ( , , reduction–oxidation or oxidation–reduction) is a type of chemical reaction in which the oxidation states of the reactants change. Oxidation is the loss of electrons or an increase in the oxidation state, while reduction is ...
degradation of gasoline during long-term storage. These harmful deposits arise from the oxidation of
alkene In organic chemistry, an alkene, or olefin, is a hydrocarbon containing a carbon–carbon double bond. The double bond may be internal or at the terminal position. Terminal alkenes are also known as Alpha-olefin, α-olefins. The Internationa ...
s and other minor components in gasoline (see
drying oil Drying is a mass transfer process consisting of the removal of water or another solvent by evaporation from a solid, semi-solid or liquid. This process is often used as a final production step before selling or packaging products. To be conside ...
s). Improvements in refinery techniques have generally reduced the susceptibility of gasolines to these problems. Previously, catalytically or thermally cracked gasolines were most susceptible to oxidation. The formation of gums is accelerated by copper salts, which can be neutralized by additives called
metal deactivator Metal deactivators, or metal deactivating agents (MDA) are fuel additives and oil additives used to stabilize fluids by deactivating (usually by sequestering) metal ions, mostly introduced by the action of naturally occurring acids in the fuel ...
s. This degradation can be prevented through the addition of 5–100 ppm of
antioxidant Antioxidants are Chemical compound, compounds that inhibit Redox, oxidation, a chemical reaction that can produce Radical (chemistry), free radicals. Autoxidation leads to degradation of organic compounds, including living matter. Antioxidants ...
s, such as
phenylenediamine Phenylenediamine may refer to: * ''o''-Phenylenediamine or OPD, a chemical compound C6H4(NH2)2 * ''m''-Phenylenediamine or MPD, a chemical compound C6H4(NH2)2 * ''p''-Phenylenediamine or PPD, a chemical compound C6H4(NH2)2 Related compounds * ''N ...
s and other
amine In chemistry, amines (, ) are organic compounds that contain carbon-nitrogen bonds. Amines are formed when one or more hydrogen atoms in ammonia are replaced by alkyl or aryl groups. The nitrogen atom in an amine possesses a lone pair of elec ...
s. Hydrocarbons with a
bromine number In chemistry, the bromine number is the amount of bromine () in grams absorbed by 100 g of a sample. The bromine number was once used as a measure of aliphatic unsaturation in gasoline and related petroleum samples, but this assay has fallen into ...
of 10 or above can be protected with the combination of unhindered or partially hindered
phenol Phenol (also known as carbolic acid, phenolic acid, or benzenol) is an aromatic organic compound with the molecular formula . It is a white crystalline solid that is volatile and can catch fire. The molecule consists of a phenyl group () ...
s and oil-soluble strong amine bases, such as hindered phenols. "Stale" gasoline can be detected by a
colorimetric Colorimetry is "the science and technology used to quantify and describe physically the human color perception". It is similar to spectrophotometry, but is distinguished by its interest in reducing spectra to the physical correlates of color p ...
enzymatic An enzyme () is a protein that acts as a biological catalyst by accelerating chemical reactions. The molecules upon which enzymes may act are called substrates, and the enzyme converts the substrates into different molecules known as produc ...
test for
organic peroxide In organic chemistry, organic peroxides are organic compounds containing the peroxide functional group (). If the R′ is hydrogen, the compounds are called hydroperoxides, which are discussed in that article. The O−O bond of peroxides easily b ...
s produced by oxidation of the gasoline. Gasolines are also treated with
metal deactivator Metal deactivators, or metal deactivating agents (MDA) are fuel additives and oil additives used to stabilize fluids by deactivating (usually by sequestering) metal ions, mostly introduced by the action of naturally occurring acids in the fuel ...
s, which are compounds that sequester (deactivate) metal salts that otherwise accelerate the formation of gummy residues. The metal impurities might arise from the engine itself or as contaminants in the fuel.


Detergents

Gasoline, as delivered at the pump, also contains additives to reduce internal engine carbon buildups, improve
combustion Combustion, or burning, is a high-temperature exothermic redox chemical reaction between a fuel (the reductant) and an oxidant, usually atmospheric oxygen, that produces oxidized, often gaseous products, in a mixture termed as smoke. Combustion ...
and allow easier starting in cold climates. High levels of detergent can be found in
Top Tier Detergent Gasoline Top Tier Detergent Gasoline and Top Tier Diesel Fuel are performance specifications and trademarks designed and supported by several automakers. BMW, General Motors, Fiat Chrysler Automobiles, Ford, Acura/Honda, Toyota, Volkswagen, Mercedes-B ...
s. The specification for Top Tier Detergent Gasolines was developed by four automakers: GM,
Honda commonly known as just Honda, is a Japanese multinational corporation, multinational Conglomerate (company), conglomerate automotive manufacturer headquartered in Minato, Tokyo, Japan. Founded in October 1946 by Soichiro Honda, Honda has bee ...
,
Toyota is a Japanese Multinational corporation, multinational Automotive industry, automotive manufacturer headquartered in Toyota City, Aichi, Japan. It was founded by Kiichiro Toyoda and incorporated on August 28, 1937. Toyota is the List of manuf ...
, and
BMW Bayerische Motoren Werke AG, trading as BMW Group (commonly abbreviated to BMW (), sometimes anglicised as Bavarian Motor Works), is a German multinational manufacturer of vehicles and motorcycles headquartered in Munich, Bavaria, Germany. Th ...
. According to the bulletin, the minimal U.S. EPA requirement is not sufficient to keep engines clean. Typical detergents include
alkylamines Alkylamines may refer to: * Aliphatic amine In chemistry, amines (, ) are organic compounds that contain carbon-nitrogen bonds. Amines are formed when one or more hydrogen atoms in ammonia are replaced by alkyl or aryl groups. The nitrogen a ...
and
alkyl phosphate Alkyl phosphates belong to a group of organic compounds called organophosphates. They are esters of phosphoric acid H3PO4 and corresponding alcohol. For example, the formula of methyl phosphate is CH3-H2PO4, dimethyl phosphate – (CH3)2HPO4 and tr ...
s at a level of 50–100 ppm.


Ethanol


European Union

In the EU, 5 percent
ethanol Ethanol (also called ethyl alcohol, grain alcohol, drinking alcohol, or simply alcohol) is an organic compound with the chemical formula . It is an Alcohol (chemistry), alcohol, with its formula also written as , or EtOH, where Et is the ps ...
can be added within the common gasoline spec (EN 228). Discussions are ongoing to allow 10 percent blending of ethanol (available in Finnish, French and German gasoline stations). In Finland, most gasoline stations sell 95E10, which is 10 percent ethanol, and 98E5, which is 5 percent ethanol. Most gasoline sold in Sweden has 5–15 percent ethanol added. Three different ethanol blends are sold in the Netherlands—E5, E10 and hE15. The last of these differs from standard ethanol–gasoline blends in that it consists of 15 percent hydrous ethanol (i.e., the ethanol–water
azeotrope An azeotrope () or a constant heating point mixture is a mixture of two or more liquids whose proportions cannot be changed by simple distillation.Moore, Walter J. ''Physical Chemistry'', 3rd e Prentice-Hall 1962, pp. 140–142 This happens beca ...
) instead of the anhydrous ethanol traditionally used for blending with gasoline. From 2009 to 2022, renewable percentage in gasoline slowly increased from 5% to 10%, even though EU-produced ethanol can achieve a climate-neutral production capability and most EU cars can use E10. E10 availability is low even in larger countries like Germany (26%) and France (58%). 8 countries in the EU have not adopted E10 as of 2024.


Brazil

The Brazilian National Agency of Petroleum, Natural Gas and Biofuels (ANP) requires gasoline for automobile use to have 27.5 percent of ethanol added to its composition. Pure hydrated ethanol is also available as a fuel.


Australia

Australia uses both E10 (up to 10% ethanol) and E85 (up to 85% ethanol) in its gasoline.
New South Wales New South Wales (commonly abbreviated as NSW) is a States and territories of Australia, state on the Eastern states of Australia, east coast of :Australia. It borders Queensland to the north, Victoria (state), Victoria to the south, and South ...
mandated biofuel in its Biofuels Act 2007, and
Queensland Queensland ( , commonly abbreviated as Qld) is a States and territories of Australia, state in northeastern Australia, and is the second-largest and third-most populous state in Australia. It is bordered by the Northern Territory, South Austr ...
had a biofuel mandate since 2017. Fuel pumps must be clearly labeled with its ethanol/biodiesel content.


U.S.

The federal
Renewable Fuel Standard The Renewable Fuel Standard (RFS) is an American federal program that requires transportation fuel sold in the United States to contain a minimum volume of renewable fuels. It originated with the Energy Policy Act of 2005 and was expanded and ext ...
(RFS) effectively requires refiners and blenders to blend renewable
biofuel Biofuel is a fuel that is produced over a short time span from Biomass (energy), biomass, rather than by the very slow natural processes involved in the formation of fossil fuels such as oil. Biofuel can be produced from plants or from agricu ...
s (mostly ethanol) with gasoline, sufficient to meet a growing annual target of total gallons blended. Although the mandate does not require a specific percentage of ethanol, annual increases in the target combined with declining
gasoline consumption The fuel economy of an Car, automobile relates to the distance traveled by a vehicle and the amount of fuel consumption, fuel consumed. Consumption can be expressed in terms of the volume of fuel to travel a distance, or the distance traveled ...
have caused the typical ethanol content in gasoline to approach 10 percent. Most fuel pumps display a sticker that states that the fuel may contain up to 10 percent ethanol, an intentional disparity that reflects the varying actual percentage. In parts of the U.S., ethanol is sometimes added to gasoline without an indication that it is a component.


India

In October 2007, the
Government of India The Government of India (ISO 15919, ISO: Bhārata Sarakāra, legally the Union Government or Union of India or the Central Government) is the national authority of the Republic of India, located in South Asia, consisting of States and union t ...
decided to make five percent ethanol blending (with gasoline) mandatory. Currently, 10 percent ethanol blended product (E10) is being sold in various parts of the country. Ethanol has been found in at least one study to damage catalytic converters.


Dyes

Though gasoline is a naturally colorless liquid, many gasolines are dyed in various colors to indicate their composition and acceptable uses. In Australia, the lowest grade of gasoline (RON 91) was dyed a light shade of red/orange, but is now the same color as the medium grade (RON 95) and high octane (RON 98), which are dyed yellow. In the U.S., aviation gasoline (
avgas Avgas (aviation gasoline, also known as aviation spirit in the United Kingdom, UK) is an aviation fuel used in aircraft with spark-ignited internal combustion engines. ''Avgas'' is distinguished from conventional gasoline (petrol) used in moto ...
) is dyed to identify its octane rating and to distinguish it from kerosene-based jet fuel, which is left colorless. In Canada, the gasoline for marine and farm use is dyed red and is not subject to fuel excise tax in most provinces.


Oxygenate blending

Oxygenate In the liquid fuel industry, oxygenates are hydrocarbon-derived fuel additives containing at least one oxygen atom to promote complete combustion. Absent oxygenates, fuel combustion is usually incomplete, and the exhaust stream pollutes the air ...
blending adds
oxygen Oxygen is a chemical element; it has chemical symbol, symbol O and atomic number 8. It is a member of the chalcogen group (periodic table), group in the periodic table, a highly reactivity (chemistry), reactive nonmetal (chemistry), non ...
-bearing compounds such as
methanol Methanol (also called methyl alcohol and wood spirit, amongst other names) is an organic chemical compound and the simplest aliphatic Alcohol (chemistry), alcohol, with the chemical formula (a methyl group linked to a hydroxyl group, often ab ...
,
MTBE Methyl ''tert''-butyl ether (MTBE), also known as ''tert''-butyl methyl ether, is an organic compound with a structural formula (CH3)3COCH3. MTBE is a volatile, flammable, and colorless liquid that is sparingly soluble in water. Primarily used as ...
,
ETBE Ethyl ''tertiary''-butyl ether (ETBE), also known as ethyl ''tert''-butyl ether, is commonly used as an oxygenate gasoline additive in the production of gasoline from crude oil. ETBE offers equal or greater air quality benefits than ethan ...
,
TAME Tame may refer to: *Taming, the act of training wild animals * River Tame, Greater Manchester *River Tame, West Midlands and the Tame Valley * Tame, Arauca, a Colombian town and municipality * "Tame" (song), a song by the Pixies from their 1989 a ...
, TAEE,
ethanol Ethanol (also called ethyl alcohol, grain alcohol, drinking alcohol, or simply alcohol) is an organic compound with the chemical formula . It is an Alcohol (chemistry), alcohol, with its formula also written as , or EtOH, where Et is the ps ...
, and
biobutanol image:Butanol_flat_structure.png, Butanol, a C-4 hydrocarbon is a promising bio-derived fuel, which shares many properties with gasoline. Butanol may be used as a fuel in an internal combustion engine. It is more similar to gasoline than it is to ...
. The presence of these oxygenates reduces the amount of
carbon monoxide Carbon monoxide (chemical formula CO) is a poisonous, flammable gas that is colorless, odorless, tasteless, and slightly less dense than air. Carbon monoxide consists of one carbon atom and one oxygen atom connected by a triple bond. It is the si ...
and unburned fuel in the exhaust. In many areas throughout the U.S., oxygenate blending is mandated by EPA regulations to reduce smog and other airborne pollutants. For example, in Southern California fuel must contain two percent oxygen by weight, resulting in a mixture of 5.6 percent ethanol in gasoline. The resulting fuel is often known as reformulated gasoline (RFG) or oxygenated gasoline, or, in the case of California, California reformulated gasoline (CARBOB). The federal requirement that RFG contain oxygen was dropped on 6 May 2006 because the industry had developed
VOC VOC, VoC or voc may refer to: Science and technology * Open-circuit voltage (VOC), the voltage between two terminals when there is no external load connected * Variant of concern, a category used during the assessment of a new variant of a virus * ...
-controlled RFG that did not need additional oxygen. MTBE was phased out in the U.S. due to groundwater contamination and the resulting regulations and lawsuits. Ethanol and, to a lesser extent, ethanol-derived ETBE are common substitutes. A common ethanol-gasoline mix of 10 percent ethanol mixed with gasoline is called
gasohol Several common ethanol fuel mixtures are in use around the world. The use of pure hydrous or anhydrous ethanol in internal combustion engines (ICEs) is only possible if the engines are designed or modified for that purpose, and used only in aut ...
or E10, and an ethanol-gasoline mix of 85 percent ethanol mixed with gasoline is called E85. The most extensive use of ethanol takes place in
Brazil Brazil, officially the Federative Republic of Brazil, is the largest country in South America. It is the world's List of countries and dependencies by area, fifth-largest country by area and the List of countries and dependencies by population ...
, where the ethanol is derived from
sugarcane Sugarcane or sugar cane is a species of tall, Perennial plant, perennial grass (in the genus ''Saccharum'', tribe Andropogoneae) that is used for sugar Sugar industry, production. The plants are 2–6 m (6–20 ft) tall with stout, jointed, fib ...
. In 2004, over of ethanol was produced in the U.S. for fuel use, mostly from
corn Maize (; ''Zea mays''), also known as corn in North American English, is a tall stout Poaceae, grass that produces cereal grain. It was domesticated by indigenous peoples of Mexico, indigenous peoples in southern Mexico about 9,000 years ago ...
and sold as E10. E85 is slowly becoming available in much of the U.S., though many of the relatively few stations vending E85 are not open to the general public. The use of bioethanol and bio-methanol, either directly or indirectly by conversion of ethanol to bio-ETBE, or methanol to bio-MTBE is encouraged by the European Union Directive on the Promotion of the use of biofuels and other renewable fuels for transport. Since producing bioethanol from fermented sugars and starches involves
distillation Distillation, also classical distillation, is the process of separating the component substances of a liquid mixture of two or more chemically discrete substances; the separation process is realized by way of the selective boiling of the mixt ...
, though, ordinary people in much of Europe cannot legally ferment and distill their own bioethanol at present (unlike in the U.S., where getting a BATF distillation permit has been easy since the 1973 oil crisis).


Safety


Toxicity

The safety data sheet for a 2003 Texas, Texan unleaded gasoline shows at least 15 hazardous chemicals occurring in various amounts, including
benzene Benzene is an Organic compound, organic chemical compound with the Chemical formula#Molecular formula, molecular formula C6H6. The benzene molecule is composed of six carbon atoms joined in a planar hexagonal Ring (chemistry), ring with one hyd ...
(up to five percent by volume),
toluene Toluene (), also known as toluol (), is a substituted aromatic hydrocarbon with the chemical formula , often abbreviated as , where Ph stands for the phenyl group. It is a colorless, water Water is an inorganic compound with the c ...
(up to 35 percent by volume), naphthalene (up to one percent by volume), 1,2,4-Trimethylbenzene, trimethylbenzene (up to seven percent by volume), Methyl tert-butyl ether, methyl ''tert''-butyl ether (MTBE) (up to 18 percent by volume, in some states), and about 10 others. Hydrocarbons in gasoline generally exhibit low acute toxicities, with LD50 of 700–2700 mg/kg for simple aromatic compounds. Benzene and many antiknocking additives are carcinogenic. People can be exposed to gasoline in the workplace by swallowing it, breathing in vapors, skin contact, and eye contact. Gasoline is toxic. The National Institute for Occupational Safety and Health (NIOSH) has also designated gasoline as a carcinogen. Physical contact, ingestion, or inhalation can cause health problems. Since ingesting large amounts of gasoline can cause permanent damage to major organs, a call to a local poison control center or emergency room visit is indicated. Contrary to common misconception, swallowing gasoline does not generally require special emergency treatment, and inducing vomiting does not help, and can make it worse. According to poison specialist Brad Dahl, "even two mouthfuls wouldn't be that dangerous as long as it goes down to your stomach and stays there or keeps going". The U.S. Centers for Disease Control and Prevention, CDC's Agency for Toxic Substances and Disease Registry says not to induce vomiting, lavage, or administer Activated carbon, activated charcoal.


Inhalation for intoxication

Inhalant, Inhaled (huffed) gasoline vapor is a common intoxicant. Users concentrate and inhale gasoline vapor in a manner not intended by the manufacturer to produce euphoria and Substance intoxication, intoxication. Gasoline inhalation has become epidemic in some poorer communities and indigenous groups in Australia, Canada, New Zealand, and some Pacific Islands. The practice is thought to cause severe organ damage, along with other effects such as intellectual disability and various cancers. In Canada, Native children in the isolated Northern Labrador community of Davis Inlet, Newfoundland and Labrador, Davis Inlet were the focus of national concern in 1993, when many were found to be sniffing gasoline. The Canadian and provincial Newfoundland and Labrador governments intervened on several occasions, sending many children away for treatment. Despite being moved to the new community of Natuashish, Newfoundland and Labrador, Natuashish in 2002, serious inhalant abuse problems have continued. Similar problems were reported in Sheshatshiu, Newfoundland and Labrador, Sheshatshiu in 2000 and also in Pikangikum First Nation. In 2012, the issue once again made the news media in Canada. Australia has long faced a petrol (gasoline) sniffing problem in isolated and impoverished Australian Aborigines, aboriginal communities. Although some sources argue that sniffing was introduced by U.S. Soldier, servicemen stationed in the nation's Top End during World War II or through experimentation by 1940s-era Cobourg Peninsula sawmill workers, other sources claim that inhalant abuse (such as glue inhalation) emerged in Australia in the late 1960s. Chronic, heavy petrol sniffing appears to occur among remote, impoverished Indigenous Australians, indigenous communities, where the ready accessibility of petrol has helped to make it a common substance for abuse. In Australia, petrol sniffing now occurs widely throughout remote Aboriginal communities in the Northern Territory, Western Australia, northern parts of South Australia, and
Queensland Queensland ( , commonly abbreviated as Qld) is a States and territories of Australia, state in northeastern Australia, and is the second-largest and third-most populous state in Australia. It is bordered by the Northern Territory, South Austr ...
. The number of people sniffing petrol goes up and down over time as young people experiment or sniff occasionally. "Boss", or chronic, sniffers may move in and out of communities; they are often responsible for encouraging young people to take it up. In 2005, the Government of Australia and BP, BP Australia began the usage of Opal (fuel), Opal fuel in remote areas prone to petrol sniffing. Opal is a non-sniffable fuel (which is much less likely to cause a high) and has made a difference in some indigenous communities.


Flammability

Gasoline is flammable with low flash point of . Gasoline has a lower explosive limit of 1.4 percent by volume and an upper explosive limit of 7.6 percent. If the concentration is below 1.4 percent, the air-gasoline mixture is too lean and does not ignite. If the concentration is above 7.6 percent, the mixture is too rich and also does not ignite. However, gasoline vapor rapidly mixes and spreads with air, making unconstrained gasoline quickly flammable.


Gasoline exhaust

The exhaust gas generated by burning gasoline is harmful to both the environment and to human health. After CO is inhaled into the human body, it readily combines with hemoglobin in the blood, and its affinity is 300 times that of oxygen. Therefore, the hemoglobin in the lungs combines with CO instead of oxygen, causing the human body to be Hypoxia (medical), hypoxic, causing headaches, dizziness, vomiting, and other poisoning symptoms. In severe cases, it may lead to death. Hydrocarbons only affect the human body when their concentration is quite high, and their toxicity level depends on the chemical composition. The hydrocarbons produced by incomplete combustion include alkanes, aromatics, and aldehydes. Among them, a concentration of methane and ethane over will cause loss of consciousness or suffocation, a concentration of pentane and hexane over will have an anesthetic effect, and aromatic hydrocarbons will have more serious effects on health, blood toxicity, neurotoxicity, and cancer. If the concentration of benzene exceeds 40 ppm, it can cause leukemia, and xylene can cause headache, dizziness, nausea, and vomiting. Human exposure to large amounts of aldehydes can cause eye irritation, nausea, and dizziness. In addition to carcinogenic effects, long-term exposure can cause damage to the skin, liver, kidneys, and cataracts. After NOx enters the alveoli, it has a severe stimulating effect on the lung tissue. It can irritate the conjunctiva of the eyes, cause tearing, and cause pink eyes. It also has a stimulating effect on the nose, pharynx, throat, and other organs. It can cause acute wheezing, breathing difficulties, red eyes, sore throat, and dizziness causing poisoning. Fine particulate matter, Fine particulates are also dangerous to health.


Environmental effect

The air pollution in many large cities has changed from coal-burning pollution to "motor vehicle pollution". In the U.S., transportation is the largest source of carbon emissions, accounting for 30 percent of the total carbon footprint of the U.S. Combustion of gasoline produces of carbon dioxide, a greenhouse gas. Unburnt gasoline and Automobile emissions control#Evaporative emissions control, evaporation from the tank, when in the atmosphere, react in sunlight to produce photochemical smog. Vapor pressure initially rises with some addition of ethanol to gasoline, but the increase is greatest at 10 percent by volume. At higher concentrations of ethanol above 10 percent, the vapor pressure of the blend starts to decrease. At a 10 percent ethanol by volume, the rise in vapor pressure may potentially increase the problem of photochemical smog. This rise in vapor pressure could be mitigated by increasing or decreasing the percentage of ethanol in the gasoline mixture. The chief risks of such leaks come not from vehicles, but gasoline delivery truck accidents and leaks from storage tanks. Because of this risk, most (underground) storage tanks now have extensive measures in place to detect and prevent any such leaks, such as monitoring systems (Veeder-Root, Franklin Fueling). Production of gasoline consumes of
water Water is an inorganic compound with the chemical formula . It is a transparent, tasteless, odorless, and Color of water, nearly colorless chemical substance. It is the main constituent of Earth's hydrosphere and the fluids of all known liv ...
by driven distance. Gasoline use causes a variety of deleterious effects to the human population and to the climate generally. The harms imposed include a higher rate of premature death and ailments, such as asthma, caused by air pollution, higher healthcare costs for the public generally, decreased crop yields, missed work and school days due to illness, increased flooding and other extreme weather events linked to global climate change, and other social costs. The costs imposed on society and the planet are estimated to be $3.80 per gallon of gasoline, in addition to the price paid at the pump by the user. The damage to the health and climate caused by a gasoline-powered vehicle greatly exceeds that caused by electric vehicles. Gasoline can be released into the environment as an uncombusted liquid fuel, as a flammable liquid, or as a vapor by way of leakages occurring during its production, handling, transport and delivery. Gasoline contains known carcinogens, and gasoline Exhaust gas, exhaust is a health risk. Gasoline is often used as a recreational inhalant and can be harmful or fatal when used in such a manner. When burned, of gasoline emits about of , a greenhouse gas, contributing to human-caused climate change. Oil products, including gasoline, were responsible for about 32% of emissions worldwide in 2021.


Carbon dioxide

About of
carbon dioxide Carbon dioxide is a chemical compound with the chemical formula . It is made up of molecules that each have one carbon atom covalent bond, covalently double bonded to two oxygen atoms. It is found in a gas state at room temperature and at norma ...
(CO2) are produced from burning gasoline that does not contain ethanol. Most of the retail gasoline now sold in the U.S. contains about 10 percent fuel ethanol (or E10) by volume. Burning E10 produces about of CO2 that is emitted from the fossil fuel content. If the CO2 emissions from ethanol combustion are considered, then about of CO2 are produced when E10 is combusted. Worldwide 7 liters of gasoline are burnt for every 100 km driven by cars and vans. In 2021, the International Energy Agency stated, "To ensure fuel economy and CO2 emissions standards are effective, governments must continue regulatory efforts to monitor and reduce the gap between real-world fuel economy and rated performance."


Contamination of soil and water

Gasoline enters the environment through the soil, groundwater, surface water, and air. Therefore, humans may be exposed to gasoline through methods such as breathing, eating, and skin contact. For example, using gasoline-filled equipment, such as lawnmowers, drinking gasoline-contaminated water close to gasoline spills or leaks to the soil, working at a gasoline station, inhaling gasoline volatile gas when refueling at a gasoline station is the easiest way to be exposed to gasoline.


Use and pricing

The International Energy Agency said in 2021 that "road fuels should be taxed at a rate that reflects their impact on people's health and the climate".


Europe

Countries in Europe impose substantially higher Fuel tax, taxes on fuels such as gasoline when compared to the U.S. The price of gasoline in Europe is typically higher than that in the U.S. due to this difference.


U.S.

From 1998 to 2004, the price of gasoline fluctuated between . After 2004, the price increased until the average gasoline price reached a high of in mid-2008 but receded to approximately by September 2009. The U.S. experienced an upswing in gasoline prices through 2011, and, by 1 March 2012, the national average was . California prices are higher because the California government mandates unique California gasoline formulas and taxes. In the U.S., most consumer goods bear pre-tax prices, but gasoline prices are posted with taxes included. Taxes are added by federal, state, and local governments. , the federal tax was for gasoline and for Diesel fuel, diesel (excluding red diesel). About nine percent of all gasoline sold in the U.S. in May 2009 was premium grade, according to the Energy Information Administration. ''Consumer Reports'' magazine says, "If [your owner's manual] says to use regular fuel, do so—there's no advantage to a higher grade." The ''Associated Press'' said premium gas—which has a higher octane rating and costs more per gallon than regular unleaded—should be used only if the manufacturer says it is "required". Cars with Turbocharger, turbocharged engines and high compression ratios often specify premium gasoline because higher octane fuels reduce the incidence of "knock", or fuel pre-detonation. The price of gasoline varies considerably between the summer and winter months. There is a considerable difference between summer oil and winter oil in gasoline vapor pressure (Reid Vapor Pressure, RVP), which is a measure of how easily the fuel evaporates at a given temperature. The higher the gasoline volatility (the higher the RVP), the easier it is to evaporate. The conversion between the two fuels occurs twice a year, once in autumn (winter mix) and the other in spring (summer mix). The winter blended fuel has a higher RVP because the fuel must be able to evaporate at a low temperature for the engine to run normally. If the RVP is too low on a cold day, the vehicle will be difficult to start; however, the summer blended gasoline has a lower RVP. It prevents excessive evaporation when the outdoor temperature rises, reduces ozone emissions, and reduces smog levels. At the same time, vapor lock is less likely to occur in hot weather.


Gasoline production by country


Comparison with other fuels

Below is a table of the energy density (per volume) and specific energy (per mass) of various transportation fuels as compared with gasoline. In the rows with Higher heating value, gross and Lower heating value, net, they are from the Oak Ridge National Laboratory's Transportation Energy Data Book.


See also

Chevron published a free high-quality technical guide <
Motor Gasolines Technical Review
/u> using common language that explains gasoline production, blending, and combustion in an engine. The report covers the US and other locations globally.


Explanatory notes


References


Bibliography

* Gold, Russell. ''The Boom: How Fracking Ignited the American Energy Revolution and Changed the World'' (Simon & Schuster, 2014). * Yergin, Daniel. ''The Quest: Energy, Security, and the Remaking of the Modern World'' (Penguin, 2011). * Yergin, Daniel. ''The Prize: The Epic Quest for Oil, Money, and Power'' (Buccaneer Books, 1994; latest edition: Reissue Press, 2008).
Graph of inflation-corrected historic prices, 1970–2005. Highest in 2005

The Low-Down on High Octane Gasoline


* A

, and to the Russian-Ukrainian theory of deep, abiotic petroleum origins.
What's the difference between premium and regular gas?
(from The Straight Dope)
International Fuel Prices 2005
with diesel and gasoline prices of 172 countries
EIA – Gasoline and Diesel Fuel Update

World Internet News: "Big Oil Looking for Another Government Handout", April 2006.




* [https://www.epa.gov/OMSWWW/rfgecon.htm Fuel Economy Impact Analysis of RFG] i.e. reformulated gasoline. Has lower heating value data, actual energy content is higher see higher heating value
A Refiner's Viewpoint on MOTOR FUEL QUALITY
, 'A Refiner's Viewpoint on Motor Fuel Quality' About the fuel specs refiners can control. Holaday W, and Happel J. (SAE paper 430113, 1943).


External links


CNN/Money: Global gas prices

EEP: European gas prices

Transportation Energy Data Book

Energy Supply Logistics Searchable Directory of US Terminals

High octane fuel, leaded and LRP gasoline—article from robotpig.net



Comparison of Regular, Midgrade, and Premium Fuel
;Images *
Down the Gasoline Trail
' Handy Jam Organization, 1935 (Down the Gasoline Trail, Cartoon) {{Authority control IARC Group 1 carcinogens Inhalants Liquid fuels Petroleum products