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Several common ethanol fuel mixtures are in use around the world. The use of pure hydrous or anhydrous
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
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 (ICEs) is only possible if the engines are designed or modified for that purpose, and used only in
automobile A car, or an automobile, is a motor vehicle with wheels. Most definitions of cars state that they run primarily on roads, Car seat, seat one to eight people, have four wheels, and mainly transport private transport#Personal transport, peopl ...
s, light-duty trucks and motorcycles. Anhydrous ethanol can be blended with :gasoline (petrol) for use in gasoline engines, but with high ethanol content only after engine modifications to meter increased fuel volume since pure ethanol contains only 2/3 of the BTUs of an equivalent volume of pure gasoline. High percentage ethanol mixtures are used in some racing engine applications as the very high octane rating of ethanol is compatible with very high compression ratios. Ethanol fuel mixtures have "E" numbers which describe the percentage of ethanol fuel in the mixture by volume, for example, E85 is 85% anhydrous ethanol and 15% gasoline. Low-ethanol blends are typically from E5 to E25, although internationally the most common use of the term refers to the E10 blend. Blends of E10 or less are used in more than 20 countries around the world, led by the United States, where ethanol represented 10% of the U.S. gasoline fuel supply in 2011. ''See pp. 10'' Blends from E20 to E25 have been used in Brazil since the late 1970s. E85 is commonly used in the U.S. and Europe for flexible-fuel vehicles. Hydrous ethanol or E100 is used in Brazilian neat ethanol vehicles and flex-fuel light vehicles and hydrous E15 called hE15 for modern petrol cars in the Netherlands.


E10 or less

E10, 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 ...
mixture of 10% anhydrous ethanol and 90% gasoline sometimes called gasohol, can be used in the
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 of most modern
automobile A car, or an automobile, is a motor vehicle with wheels. Most definitions of cars state that they run primarily on roads, Car seat, seat one to eight people, have four wheels, and mainly transport private transport#Personal transport, peopl ...
s and light-duty vehicles without need for any modification on the engine or fuel system. E10 blends are typically rated as being 2 to 3 octane numbers higher than regular gasoline and are approved for use in all new U.S. automobiles, and mandated in some areas for emissions and other reasons. Other common blends include E5 and E7. These concentrations are generally safe for recent engines that should run on pure gasoline. As of 2006, mandates for blending bioethanol into vehicle fuels had been enacted in at least 36 states/provinces and 17 countries at the national level, with most mandates requiring a blend of 10 to 15% ethanol with gasoline. One measure of alternative fuels in the U.S. is the "
gasoline-equivalent gallon Gasoline gallon equivalent (GGE) or gasoline-equivalent gallon (GEG) is the amount of an alternative fuel it takes to equal the energy content of one liquid gallon of gasoline. GGE allows consumers to compare the energy content of competing fue ...
" (GEG). In 2002, the U.S. used as motor fuel, ethanol equal to , the energy equivalent of of gasoline. This was less than 1% of the total fuel used that year. E10 and other blends of ethanol are considered to be useful in decreasing U.S. dependence on foreign oil, and can reduce
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 ...
(CO) emissions by 20 to 30% under the right conditions. Although E10 does decrease emissions of CO and greenhouse gases such as CO2 by an estimated 2% over regular gasoline, it can cause increases in evaporative emissions and some pollutants depending on factors such as the age of the vehicle and weather conditions. According to the Philippine Department of Energy, the use of up to 10% ethanol-gasoline mixture is not harmful to cars' fuel systems. Generally, automobile gasoline containing alcohol (ethanol or methanol) is not recommended to be used in aircraft.


Availability

* E10 became the standard fuel at petrol stations in the United Kingdom as of September 2021. * E10 was introduced nationwide in Thailand in 2007, and replaced 91 octane pure gasoline in that country in 2013. * E10 is commonly available in the
Midwestern United States The Midwestern United States (also referred to as the Midwest, the Heartland or the American Midwest) is one of the four census regions defined by the United States Census Bureau. It occupies the northern central part of the United States. It ...
. It was also mandated for use in all standard automobile fuel in the state of Florida by the end of 2010. Due to the phasing out of
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 ...
as a gasoline additive and mainly due to the mandates established in the
Energy Policy Act of 2005 The Energy Policy Act of 2005 () is a federal law signed by President George W. Bush on August 8, 2005, at Sandia National Laboratories in Albuquerque, New Mexico. The act, described by proponents as an attempt to combat growing energy problems ...
and the
Energy Independence and Security Act of 2007 The Energy Independence and Security Act of 2007Pub.L. 110-140, originally named the Clean Energy Act of 2007, is an Act of Congress concerning the energy policy of the United States. As part of the United States Democratic Party, Democratic Pa ...
, ethanol blends have increased throughout the United States, and by 2009, the ethanol market share in the U.S. gasoline supply reached almost 8% by volume. * Mandatory blending of ethanol was approved in Mozambique, but the percentage in the blend has not been specified. * South Africa approved a biofuel strategy in 2007, and mandated an 8% blend of ethanol by 2013. * A 2007 Uruguayan law mandates a minimum of 5% of ethanol blended with gasoline starting in January 2015. The monopolic, state-owned fuel producer ANCAP started blending premium gasoline with 10% of bioethanol in December 2009, which will be available in all the country by early January 2010. *The Dominican Republic has a mandate for blending 15% of ethanol by 2015. *Chile is considering the introduction of E5, and Panama, Bolivia and Venezuela of E10. *India achieved the target of 10 percent ethanol blending, 5 months ahead of schedule, in June 2022. *From January 2018, all 92-octane fuel in Vietnam is mandated to contain 5 percent ethanol (E5). No ethanol blending is required for 95-octane fuel. *From June 2021, Argentina approved an E12 minimum (Law 27640), and after October 2022 a waiver for a maximum of E15.
A 2011 study conducted by VTT Technical Research Centre of Finland found practically no difference in fuel consumption in normal driving conditions between commercial gasoline grades 95E10 and 98E5 sold in Finland, despite the public perception that fuel consumption is significantly higher with 95E10. VTT performed the comparison test under controlled laboratory conditions and their measurements showed that over a distance of , the cars tested used an average of of 95E10, as opposed to of 98E5. The difference was 0.07 in favor of 98E5 on average, meaning that using 95E10 gasoline, which has a higher ethanol content, increases consumption by 0.7%. When the measurements are normalized, the difference becomes 1.0%, a result that is highly consistent with an estimation of calorific values based on approximate fuel composition, which came out at 1.1% in favour of E5.


Sweden

In Sweden, all 95-octane gasoline is E10 (6 to 10 percent of ethanol) since 1 August 2021, when the proportion of ethanol was increased from E5. In the early-mid-1990s, some fuel chains also sold E10. All newer and many older petrol cars bought in Sweden should handle this, since from January 2011, the Fuel Quality Directive (Directive 2009/30/EC) applied through its transposition into the law of Sweden as a member of the 27 member states of the EU.


E15

E15 contains 15% ethanol and 85% gasoline. This is generally the highest ratio of ethanol to gasoline that is possible to use in vehicles recommended by some auto manufacturers to run on E10 in the US. This is due to ethanol's hydrophilia and solvent power. As a result of the
Energy Independence and Security Act of 2007 The Energy Independence and Security Act of 2007Pub.L. 110-140, originally named the Clean Energy Act of 2007, is an Act of Congress concerning the energy policy of the United States. As part of the United States Democratic Party, Democratic Pa ...
, which mandates an increase in renewable fuels for the transport sector, the U.S. Department of Energy began assessments for the feasibility of using intermediate ethanol blends in the existing vehicle fleet as a way to allow higher consumption of ethanol fuel. The National Renewable Energy Laboratory (NREL) conducted tests to evaluate the potential impacts of intermediate ethanol blends on legacy vehicles and other engines. In a preliminary report released in October 2008, the NREL presented the results of the first evaluations of the effects of E10, E15 and E20 gasoline blends on tailpipe and evaporative emissions, catalyst and engine durability, vehicle driveability, engine operability, and vehicle and engine materials. This preliminary report found none of the vehicles displayed a malfunction indicator light as a result of the ethanol blend used; no fuel filter plugging symptoms were observed; no cold start problems were observed at and laboratory conditions; and as expected, computer technology available in newer model vehicles adapts to the higher octane causing lower emissions with greater horsepower and in some cases greater fuel economy. NREL/TP-540-43543, ORNL/TM-2008/117 Other sources make the opposite claim about fuel economy. According to
Consumer Reports Consumer Reports (CR), formerly Consumers Union (CU), is an American nonprofit consumer organization dedicated to independent product testing, investigative journalism, consumer-oriented research, public education, and consumer advocacy. Founded ...
, "ethanol isn’t as energy-dense as regular gasoline so you will see worse fuel economy with E15 gas.” In March 2009, a lobbying group from the ethanol industry, Growth Energy, formally requested the U.S. Environmental Protection Agency (EPA) to allow the ethanol content in gasoline to be increased from 10% to 15%. Organizations doing such studies included the Energy Department, the State of Minnesota, the Renewable Fuels Association, the
Rochester Institute of Technology The Rochester Institute of Technology (RIT) is a private university, private research university in Henrietta, New York, a suburb of Rochester, New York, Rochester. It was founded in 1829. It is one of only two institute of technology, institut ...
, the Minnesota Center for Automotive Research, and
Stockholm University Stockholm University (SU) () is a public university, public research university in Stockholm, Sweden, founded as a college in 1878, with university status since 1960. With over 33,000 students at four different faculties: law, humanities, social ...
in Sweden. In October 2010, the EPA granted a waiver to allow up to 15% of ethanol blended with gasoline to be sold only for cars and light pickup trucks with a model year of 2007 or later, representing about 15% of vehicles on U.S. roads. In January 2011, the waiver was expanded to authorize use of E15 to include model year 2001 through 2006 passenger vehicles. The EPA also decided not to grant any waiver for E15 use in any motorcycles, heavy-duty vehicles, or nonroad engines because current testing data do not support such a waiver. According to the Renewable Fuels Association, the E15 waivers now cover 62% of vehicles on the road in the US, and the ethanol group estimates if all 2001 and newer cars and pickups were to use E15, the theoretical blend wall for ethanol use would be approximately 17.5 billion gallons (66.2 billion liters) per year. The EPA was still studying if older cars can withstand a 15% ethanol blend. The EPA waiver authorizes sale of E15 only from Sep 15 to May 31 out of a black hose and a yellow hose to flex fuel vehicles only from June 1 to Sep 14. Retailers have shunned building infrastructure due to the costly regulatory requirements which have created a practical barrier to the commercialization of the higher blend. Most fuel stations do not have enough pumps to offer the new blend, few existing pumps are certified to dispense E15, and no dedicated tanks are readily available to store E15. Also, some state and federal regulations would have to change before E15 can be legally sold. The National Association of Convenience Stores, which represents most gasoline retailers, considers the potential for actual E15 demand is small, "because the auto industry is not embracing the fuel and is not adjusting their warranties or recommendations for the fuel type." One possible solution to the infrastructure barriers is the introduction of blender pumps that allow consumers to turn a dial to select the level of ethanol, which would also allow owners of flexible-fuel cars to buy E85 fuel. In June 2011 EPA, in cooperation with the
Federal Trade Commission The Federal Trade Commission (FTC) is an independent agency of the United States government whose principal mission is the enforcement of civil (non-criminal) United States antitrust law, antitrust law and the promotion of consumer protection. It ...
, issued its final ruling regarding the E15 warning label required to be displayed in all E15 fuel dispensers in the U.S. to inform consumers about what vehicles can, and what vehicles and equipment cannot, use the E15 blend. Both the Alliance of Automobile Manufacturers and the National Petrochemical and Refiners Association complained that relying solely on this warning label is not enough to protect consumers from misfueling. In July 2012, a fueling station in
Lawrence, Kansas Lawrence is a city in and the county seat of Douglas County, Kansas, United States, and the sixth-largest city in the state. It is in the northeastern sector of the state, astride Interstate 70 in Kansas, Interstate 70, between the Kansas River ...
became the first in the U.S. to sell the E15 blend. The fuel is sold through a blender pump that allows customers to choose between E10, E15, E30 or E85, with the latter blends sold only to flexible-fuel vehicles. , there are about 24 fueling stations selling E15 out of 180,000 stations across the U.S. In December 2010, several groups, including the Alliance of Automobile Manufacturers, the
American Petroleum Institute The American Petroleum Institute (API) is the largest U.S. trade association for the oil and natural gas industry. It claims to represent nearly 600 corporations involved in extraction of petroleum, production, oil refinery, refinement, pipeline ...
, the Association of International Automobile Manufacturers, the National Marine Manufacturers Association, the Outdoor Power Equipment Institute, and the
Grocery Manufacturers Association The Consumer Brands Association (CBA), formerly the Grocery Manufacturers Association (GMA), is a United States-wide trade association for manufacturers of consumer packaged goods (CPG). The CBA represents companies that manufacture food, beve ...
, filed suit against the EPA in the
United States Court of Appeals for the District of Columbia Circuit The United States Court of Appeals for the District of Columbia Circuit (in case citations, D.C. Cir.) is one of the thirteen United States Courts of Appeals. It has the smallest geographical jurisdiction of any of the U.S. courts of appeals, ...
. The plaintiffs argued the EPA does not have the authority to issue a “partial waiver” that covers some cars and not others. Among other arguments, the groups argued that the higher ethanol blend is not only a problem for cars, but also for fuel pumps and underground tanks not designed for the E15 mixture. It was also argued that the rise in ethanol has contributed to the big jump in corn prices in recent years. In August 2012, the federal appeals court rejected the suit against the EPA. The case was thrown out on a technical reason, as the court ruled the groups did not have legal standing to challenge EPA's decision to issue the waiver for E15. In June 2013 the U.S. Supreme Court declined to hear an appeal from industry groups opposed to the EPA ruling about E15, and let the 2012 federal appeals court ruling stand. , sales of E15 are not authorized in California, and according to the California Air Resources Board (CARB), the blend is still awaiting approval, and in a public statement the agency said that "''it would take several years to complete the vehicle testing and rule development necessary to introduce a new transportation fuel into California's market''." According to a survey conducted by the American Automobile Association (AAA) in 2012, only about 12 million out of the more than 240 million light-duty vehicles on the U.S. roads in 2012 are approved by manufacturers are fully compliant with E15 gasoline. According with the association,
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 ...
,
Chrysler FCA US, LLC, Trade name, doing business as Stellantis North America and known historically as Chrysler ( ), is one of the "Big Three (automobile manufacturers), Big Three" automobile manufacturers in the United States, headquartered in Auburn H ...
,
Nissan is a Japanese multinational Automotive industry, automobile manufacturer headquartered in Yokohama, Kanagawa, Japan. The company sells its vehicles under the ''Nissan'' and ''Infiniti'' brands, and formerly the ''Datsun'' brand, with in-house ...
,
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
Volkswagen Volkswagen (VW; )English: , . is a German automotive industry, automobile manufacturer based in Wolfsburg, Lower Saxony, Germany. Established in 1937 by German Labour Front, The German Labour Front, it was revitalized into the global brand it ...
warned that their warranties will not cover E15-related damage. Despite the controversy, in order to adjust to EPA regulations, 2012 and 2013 model year vehicles manufactured by
General Motors General Motors Company (GM) is an American Multinational corporation, multinational Automotive industry, automotive manufacturing company headquartered in Detroit, Michigan, United States. The company is most known for owning and manufacturing f ...
can use fuel containing up to 15 percent ethanol, as indicated in the vehicle owners' manuals. However, the carmaker warned that for model year 2011 or earlier vehicles, they "strongly recommend that GM customers refer to their owners manuals for the proper fuel designation for their vehicles."
Ford Motor Company Ford Motor Company (commonly known as Ford) is an American multinational corporation, multinational automobile manufacturer headquartered in Dearborn, Michigan, United States. It was founded by Henry Ford and incorporated on June 16, 1903. T ...
also is manufacturing all of its 2013 vehicles E15 compatible, including hybrid electrics and vehicles with Ecoboost engines. Also
Porsche Dr. Ing. h.c. F. Porsche AG, usually shortened to Porsche (; see below), is a German automobile manufacturer specializing in luxury, high-performance sports cars, SUVs and sedans, headquartered in Stuttgart, Baden-Württemberg, Germany. Th ...
s built since 2001 are approved by its manufacturer to use E15. Volkswagen announced that for the 2014 model year, its entire lineup will be E15 capable.
Fiat Chrysler Automobiles Fiat Chrysler Automobiles N.V. (FCA), now part of Stellantis, was an Italian-American multinational corporation primarily known as a manufacturer of Car, automobiles, commercial vehicles, List of auto parts, auto parts and production systems. ...
announced in August 2015 that all 2016 model year
Chrysler FCA US, LLC, Trade name, doing business as Stellantis North America and known historically as Chrysler ( ), is one of the "Big Three (automobile manufacturers), Big Three" automobile manufacturers in the United States, headquartered in Auburn H ...
/
Fiat Fiat Automobiles S.p.A., commonly known as simply Fiat ( , ; ), is an Italian automobile manufacturer. It became a part of Fiat Chrysler Automobiles in 2014 and, in 2021, became a subsidiary of Stellantis through its Italian division, Stellant ...
,
Jeep Jeep is an American automobile brand, now owned by multi-national corporation Stellantis. Jeep has been part of Chrysler since 1987, when Chrysler acquired the Jeep brand, along with other assets, from its previous owner, American Motors Co ...
,
Dodge Dodge is an American brand of automobiles and a division of Stellantis, based in Auburn Hills, Michigan. Dodge vehicles have historically included performance cars, and for much of its existence, Dodge was Chrysler's mid-priced brand above P ...
and Ram vehicles will be E15 compatible. In November 2013, the Environmental Protection Agency opened for public comment its proposal to reduce the amount of ethanol required in the U.S. gasoline supply as mandated by the
Energy Independence and Security Act of 2007 The Energy Independence and Security Act of 2007Pub.L. 110-140, originally named the Clean Energy Act of 2007, is an Act of Congress concerning the energy policy of the United States. As part of the United States Democratic Party, Democratic Pa ...
. The agency cited problems with increasing the blend of ethanol above 10%. This limit, known as the "blend wall," refers to the practical difficulty in incorporating increasing amounts of ethanol into the transportation fuel supply at volumes exceeding those achieved by the sale of nearly all gasoline as E10.


hE15

A 15% hydrous ethanol and 85% gasoline blend, hE15, has been introduced at public gas stations in the Netherlands since 2008. Ethanol fuel specifications worldwide traditionally dictate use of anhydrous ethanol (less than 1% water) for gasoline blending. This results in additional costs, energy usage and environmental impacts associated with the extra processing step required to dehydrate the hydrous ethanol produced via distillation (3.5-4.9 vol.% water) to meet the current anhydrous ethanol specifications. A patented discovery reveals hydrous ethanol can be effectively used in most ethanol/gasoline blending applications. According to the Brazilian Agência Nacional do Petróleo (ANP) specification, hydrous ethanol contains up to 4.9 vol.% water. In hE15, this would be up to 0.74 vol.% water in the overall mixture. Japanese and German scientific evidence revealed the water is an inhibitor for corrosion by ethanol. The experiments show that water in fuel ethanol inhibits dry corrosion. At 10,000 ppm water in the E50 experiments by JARI and 3,500 ppm water in the E20 experiments by TU Darmstadt the alcoholate/alkoxide corrosion stopped. In the fuel ethanol this resembles 20,000 ppm or 2 volume% in the case of JARI and 5 x 3500 = 17,500 ppm of 1.75 volume% in the case of TU Darmstadt. The observations are in line with the fact that hydrous ethanol is known for being less corrosive than anhydrous ethanol. The reaction mechanism will be the same at lower-mid blends. When enough water is present in the fuel, the aluminum will react preferably with water to produce aluminum oxide, repairing the protective aluminum oxide layer, which is why the corrosion stops. The aluminum alcoholate/alkoxide does not make a tight oxide layer, which is why the corrosion continues. In other words, water is essential to repair the holes in the oxide layer. Based on the Japanese/German results, a minimum of 2 vol.% or 2.52% m/m water is currently proposed in the revision of the hydrous ethanol specification for blending in petrol at E10+ levels. Water injection has additional positive effects on the engine performance (thermodynamic efficiency) and reduces overall CO2 emissions. Overall, a transition from anhydrous to hydrous ethanol for gasoline blending is expected to make a significant contribution to ethanol's cost-competitiveness, fuel cycle net energy balance, air quality, and greenhouse gas emissions. The level of blending above 10% (V/V) is chosen both from a technical (safety) perspective and to distinguish the product in Europe from regular unleaded petrol for reasons of taxes and customer clarity. Small-scale tests have shown many vehicles with modern engine types can run smoothly on this hydrous ethanol blend. Mixed tanking scenarios with anhydrous ethanol blends at 5% or 10% level do not induce phase separation. As avoiding mixing with E0, in particular at extremely low temperatures, in logistic systems and engines is not recommended, a separate specification for controlled usage is presented in a Netherlands Technical Agreement NTA 8115. The NTA 8115 is written for a worldwide application in trading and fuel blending.


E20, E25

E20 contains 20% ethanol and 80% gasoline, while E25 contains 25% ethanol. These blends have been widely used in Brazil since the late 1970s. As a response to the
1973 oil crisis In October 1973, the Organization of Arab Petroleum Exporting Countries (OAPEC) announced that it was implementing a total oil embargo against countries that had supported Israel at any point during the 1973 Yom Kippur War, which began after Eg ...
, the Brazilian government made mandatory the blend of ethanol fuel with gasoline, fluctuating between 10% and 22% from 1976 until 1992. Ph.D. Dissertation Thesis, pp. 81-82 Due to this mandatory minimum gasoline blend, pure gasoline (E0) is no longer sold in Brazil. A federal law was passed in October 1993 establishing a mandatory blend of 22% anhydrous ethanol (E22) in the entire country. This law also authorized the Executive to set different percentages of ethanol within pre-established boundaries, and since 2003, these limits were fixed at a maximum of 25% (E25) and a minimum of 20% (E20) by volume. See article 9º and modifications approved by Law Nº 10.696, 2003-07-02 Since then, the government has set the percentage on the ethanol blend according to the results of the
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 ...
harvest and ethanol production from sugarcane, resulting in blend variations even within the same year. Since July 1, 2007, the mandatory blend was set at 25% of anhydrous ethanol (E25) by executive decree, This decree fixed the mandatory blend at 25% starting July 1, 2007 and this has been the standard gasoline blend sold throughout Brazil most of the time as of 2011. However, as a result of a supply shortage and the resulting high ethanol fuel prices, in 2010, the government mandated a temporary 90-day blend reduction from E25 to E20 beginning February 1, 2010. As prices rose abruptly again due to supply shortages that took place again between the 2010 and 2011 harvest seasons, some ethanol had to be imported from the United States, and in April 2011, the government reduced the minimum mandatory blend to 18%, leaving the mandatory blend range between E18 and E25. All Brazilian automakers have adapted their gasoline engines to run smoothly with this range of mixtures, thus, all gasoline vehicles are built to run with blends from E20 to E25, defined by local law as "common gasoline type C". Some vehicles might work properly with lower concentrations of ethanol, but with a few exceptions, they are unable to run smoothly with pure gasoline, which causes engine knocking, as vehicles traveling to neighboring South American countries have demonstrated. Flex-fuel vehicles, which can run on any type of gasoline E20-E25 up to 100% hydrous
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 ...
(E100 or hydrated ethanol) ratios, were first available in mid-2003. In July 2008, 86% of all new light vehicles sold in Brazil were flexible-fuel, and only two carmakers build models with a flex-fuel engine optimized to operate with pure gasoline (E0):
Renault Renault S.A., commonly referred to as Groupe Renault ( , , , also known as the Renault Group in English), is a French Multinational corporation, multinational Automotive industry, automobile manufacturer established in 1899. The company curr ...
with the models
Clio In Greek mythology, Clio ( , ; ), also spelled Kleio, Сleio, or Cleo, is the muse of history, or in a few mythological accounts, the muse of lyre-playing. Etymology Clio's name is derived from the Greek root κλέω/κλείω (meaning ...
,
Symbol A symbol is a mark, Sign (semiotics), sign, or word that indicates, signifies, or is understood as representing an idea, physical object, object, or wikt:relationship, relationship. Symbols allow people to go beyond what is known or seen by cr ...
, Logan, Sandero and Mégane, and
Fiat Fiat Automobiles S.p.A., commonly known as simply Fiat ( , ; ), is an Italian automobile manufacturer. It became a part of Fiat Chrysler Automobiles in 2014 and, in 2021, became a subsidiary of Stellantis through its Italian division, Stellant ...
with the Siena Tetrafuel. Thailand introduced E20 in 2008, but shortages in ethanol supplies by mid-2008 caused a delay in the expansion of the E20 fueling station network in the country. By mid-2010, 161 fueling stations were selling E20, and sales have risen 80% since April 2009. The rapid growth in E20 demand is because most vehicle models launched since 2009 were E20-compatible, and sales of E20 are expected to grow faster once more local automakers start producing small, E20-compatible, fuel-efficient cars. The Thai government is promoting ethanol usage through subsidies, as ethanol costs four baht (about 12 US cents) a litre more than gasoline. A state law approved in
Minnesota Minnesota ( ) is a U.S. state, state in the Upper Midwestern region of the United States. It is bordered by the Canadian provinces of Manitoba and Ontario to the north and east and by the U.S. states of Wisconsin to the east, Iowa to the so ...
in 2005 mandated that ethanol comprise 20% of all gasoline sold in this American state beginning in 2013. Successful tests have been conducted to determine the performance under E20 by current vehicles and fuel dispensing equipment designed for E10. However, this mandate was later delayed to 2015, and has never taken effect because the federal EPA has yet to authorize the use of E20 as a replacement for gasoline. A study commissioned by BP and published in September 2013, concluded that the use of advanced biofuels in the UK, and particularly E20
cellulosic ethanol Cellulosic ethanol is ethanol (ethyl alcohol) produced from cellulose (the stringy fiber of a plant) rather than from the plant's seeds or fruit. It can be produced from grasses, wood, algae, or other plants. It is generally discussed for use as a ...
, is a more cost-effective way of reducing emissions than using plug-in electric vehicles (PEVs) in the timeframe to 2030. The study also found that the use of higher blends of biofuels is complementary to hybrid electric vehicles (HEVs) and plug-in hybrids (PHEVs).
Battery electric vehicle A battery electric vehicle (BEV), pure electric vehicle, only-electric vehicle, fully electric vehicle or all-electric vehicle is a type of electric vehicle (EV) that uses electrical energy exclusively from an electric vehicle battery, on-boa ...
s (BEVs) can deliver strong CO2 savings with a decarbonised electric grid, but are expected to have significantly higher costs than
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 ...
vehicles and hybrid cars to 2030, as the latter are expected to be the most popular models by 2030. According to the study, in 2030 an E20 blend in an HEV can achieve a 10% emission savings compared to an HEV running on E5, for an annual fuel cost premium of compared to an annual cost of for an all-electric car.


E70, E75

E70 contains 70% ethanol and 30% gasoline, while E75 contains 75% ethanol. These winter blends are used in the United States and Sweden for E85 flexible-fuel vehicles during the cold weather, but still sold at the pump labeled as E85. The seasonal reduction of the ethanol content to an E85 winter blend is mandated to avoid cold starting problems at low temperatures. In the US, this seasonal reduction of the ethanol content to E70 applies only in cold regions, where temperatures fall below during the winter. In
Wyoming Wyoming ( ) is a landlocked U.S. state, state in the Mountain states, Mountain West subregion of the Western United States, Western United States. It borders Montana to the north and northwest, South Dakota and Nebraska to the east, Idaho t ...
for example, E70 is sold as E85 from October to May. In Sweden, all E85 flexible-fuel vehicles use an E75 winter blend. This blend was introduced since the winter 2006-07 and E75 is used from November until March. For temperatures below , all E85 flex vehicles require an engine block heater to avoid cold starting problems. The use of this device is also recommended for gasoline vehicles when temperatures drop below . Another option when extreme cold weather is expected is to add more pure gasoline in the tank, thus reducing the ethanol content below the E70 winter blend, or simply not to use E85 during extreme low temperature spells.


E85

E85, a mixture of 85% ethanol and ~15% gasoline, is generally the highest ethanol fuel mixture found in the United States and several European countries, particularly in Sweden, as this blend is the standard fuel for flexible-fuel vehicles. This mixture has an
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 ...
of 108, however, the Ethanol molecule also carries with it an
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 ...
atom, where-as gasoline does not, effectively requiring the internal combustion engine to ingest less air per unit-volume by its own accord, which reduces pumping losses, and further increases the exo-thermic chemical reaction. Ethanol fuel is considered – although not widely known as – a form of "chemical supercharging", similar to that of
Nitrous Oxide Nitrous oxide (dinitrogen oxide or dinitrogen monoxide), commonly known as laughing gas, nitrous, or factitious air, among others, is a chemical compound, an Nitrogen oxide, oxide of nitrogen with the Chemical formula, formula . At room te ...
(N2O) &
Nitromethane Nitromethane, sometimes shortened to simply "nitro", is an organic compound with the chemical formula . It is the simplest organic nitro compound. It is a polar liquid commonly used as a solvent in a variety of industrial applications such as in ...
(CH3NO2). The 85% limit in the ethanol content was set to reduce ethanol emissions at low temperatures and to avoid cold starting problems during cold weather, at temperatures lower than . A further reduction in the ethanol content is used during the winter in regions where temperatures fall below and this blend is called Winter E85, as the fuel is still sold under the E85 label. A winter blend of E70 is mandated in some regions in the US, while Sweden mandates E75. Some regions in the United States now allow E51 (51% ethanol, 49% gasoline) to be sold as E85 in the winter months. As of October 2010, nearly 3,000 E85 fuel pumps were in Europe, led by Sweden with 1,699 filling stations. The United States had 3,354 public E85 fuel pumps located in 2,154 cities by August 2014, mostly concentrated in the
Midwest The Midwestern United States (also referred to as the Midwest, the Heartland or the American Midwest) is one of the four census regions defined by the United States Census Bureau. It occupies the northern central part of the United States. It ...
. Thailand introduced E85 fuel by the end of 2008, and by mid-2010, only four E85 filling stations were available, with plans to expand to 15 stations by 2012. A major restriction hampering sales of E85 flex vehicles or fuelling with E85, is the limited infrastructure available to sell E85 to the public, as by 2014 only 2 percent of motor fuel stations offered E85, up from about 1 percent in 2011. , there were only 3,218 gasoline fueling stations selling E85 to the public in the entire U.S., '', there were 3,218 stations Selling E85 across 2013 cities in the U.S.'' while about 156,000 retail motor fuel outlets do not offer the E85 blend. The number of E85 grew from 1,229 in 2007 to 2,442 in 2011, but only increased by 7% from 2011 to 2013, when the total reached 2,625. There is a great concentration of E85 stations in the Corn Belt states, and , the leading state is
Minnesota Minnesota ( ) is a U.S. state, state in the Upper Midwestern region of the United States. It is bordered by the Canadian provinces of Manitoba and Ontario to the north and east and by the U.S. states of Wisconsin to the east, Iowa to the so ...
with 274 stations, followed by
Michigan Michigan ( ) is a peninsular U.S. state, state in the Great Lakes region, Great Lakes region of the Upper Midwest, Upper Midwestern United States. It shares water and land boundaries with Minnesota to the northwest, Wisconsin to the west, ...
with 231,
Illinois Illinois ( ) is a U.S. state, state in the Midwestern United States, Midwestern United States. It borders on Lake Michigan to its northeast, the Mississippi River to its west, and the Wabash River, Wabash and Ohio River, Ohio rivers to its ...
with 225,
Iowa Iowa ( ) is a U.S. state, state in the upper Midwestern United States, Midwestern region of the United States. It borders the Mississippi River to the east and the Missouri River and Big Sioux River to the west; Wisconsin to the northeast, Ill ...
with 204,
Indiana Indiana ( ) is a U.S. state, state in the Midwestern United States, Midwestern region of the United States. It borders Lake Michigan to the northwest, Michigan to the north and northeast, Ohio to the east, the Ohio River and Kentucky to the s ...
with 188,
Texas Texas ( , ; or ) is the most populous U.S. state, state in the South Central United States, South Central region of the United States. It borders Louisiana to the east, Arkansas to the northeast, Oklahoma to the north, New Mexico to the we ...
with 181,
Wisconsin Wisconsin ( ) is a U.S. state, state in the Great Lakes region, Great Lakes region of the Upper Midwest of the United States. It borders Minnesota to the west, Iowa to the southwest, Illinois to the south, Lake Michigan to the east, Michig ...
with 152, and
Ohio Ohio ( ) is a U.S. state, state in the Midwestern United States, Midwestern region of the United States. It borders Lake Erie to the north, Pennsylvania to the east, West Virginia to the southeast, Kentucky to the southwest, Indiana to the ...
with 126. Only eight states do not have E85 available to the public,
Alaska Alaska ( ) is a non-contiguous U.S. state on the northwest extremity of North America. Part of the Western United States region, it is one of the two non-contiguous U.S. states, alongside Hawaii. Alaska is also considered to be the north ...
,
Delaware Delaware ( ) is a U.S. state, state in the Mid-Atlantic (United States), Mid-Atlantic and South Atlantic states, South Atlantic regions of the United States. It borders Maryland to its south and west, Pennsylvania to its north, New Jersey ...
,
Hawaii Hawaii ( ; ) is an island U.S. state, state of the United States, in the Pacific Ocean about southwest of the U.S. mainland. One of the two Non-contiguous United States, non-contiguous U.S. states (along with Alaska), it is the only sta ...
,
Montana Montana ( ) is a landlocked U.S. state, state in the Mountain states, Mountain West subregion of the Western United States. It is bordered by Idaho to the west, North Dakota to the east, South Dakota to the southeast, Wyoming to the south, an ...
,
Maine Maine ( ) is a U.S. state, state in the New England region of the United States, and the northeasternmost state in the Contiguous United States. It borders New Hampshire to the west, the Gulf of Maine to the southeast, and the Provinces and ...
,
New Hampshire New Hampshire ( ) is a U.S. state, state in the New England region of the Northeastern United States. It borders Massachusetts to the south, Vermont to the west, Maine and the Gulf of Maine to the east, and the Canadian province of Quebec t ...
,
Rhode Island Rhode Island ( ) is a state in the New England region of the Northeastern United States. It borders Connecticut to its west; Massachusetts to its north and east; and the Atlantic Ocean to its south via Rhode Island Sound and Block Is ...
, and
Vermont Vermont () is a U.S. state, state in the New England region of the Northeastern United States. It borders Massachusetts to the south, New Hampshire to the east, New York (state), New York to the west, and the Provinces and territories of Ca ...
. The main constraint for a more rapid expansion of E85 availability is that it requires dedicated storage tanks at filling stations, at an estimated cost of for each dedicated ethanol tank. pp. 28-30 A study conducted by the U.S. Department of Energy concluded that every service station in America could be converted to handle E85 at a cost of $3.4 billion to $10.1 billion.


ED95

ED95 designates a blend of 95% ethanol and 5% ignition improver; it is used in modified
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 where high compression is used to ignite the fuel, as opposed to the operation of gasoline engines, where spark plugs are used. This fuel was developed by Swedish ethanol producer SEKAB. Because of the high ignition temperatures of pure ethanol, the addition of ignition improver is necessary for successful
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 ...
operation. A diesel engine running on ethanol also has a higher compression ratio and an adapted fuel system. This fuel has been used with success in many Swedish
Scania Scania ( ), also known by its native name of Skåne (), is the southernmost of the historical provinces of Sweden, provinces () of Sweden. Located in the south tip of the geographical region of Götaland, the province is roughly conterminous w ...
buses since 1985, which has produced around 700 ethanol buses, more than 600 of them to Swedish cities, and more recently has also delivered ethanol buses for commercial service in Great Britain, Spain, Italy, Belgium, and Norway. As of June 2010
Stockholm Stockholm (; ) is the Capital city, capital and List of urban areas in Sweden by population, most populous city of Sweden, as well as the List of urban areas in the Nordic countries, largest urban area in the Nordic countries. Approximately ...
has the largest ethanol ED95 bus fleet in the world. As of 2010, the Swedish ED95 engine is in its third generation and already has complied with Euro 5 emission standards, without any kind of post-treatment of the exhaust gases. The ethanol-powered engine is also being certified as environmentally enhanced vehicle (EEV) in the Stockholm municipality. The EEV rule still has no date to enter into force in Europe and is stricter than the Euro 5 standard.
Nottingham Nottingham ( , East Midlands English, locally ) is a City status in the United Kingdom, city and Unitary authorities of England, unitary authority area in Nottinghamshire, East Midlands, England. It is located south-east of Sheffield and nor ...
became the first city in England to operate a regular bus service with ethanol-fuelled vehicles. Three ED95 single-deck buses entered regular service in the city in March 2008. Soon after,
Reading Reading is the process of taking in the sense or meaning of symbols, often specifically those of a written language, by means of Visual perception, sight or Somatosensory system, touch. For educators and researchers, reading is a multifacete ...
also introduced ED95 double-deck buses. Under the auspices of the BioEthanol for Sustainable Transport project, more than 138 bioethanol ED95 buses were part of demonstration trial at four cities, three in Europe, and one in Brazil, between 2006 and 2009. A total of 127 ED95 buses operated in
Stockholm Stockholm (; ) is the Capital city, capital and List of urban areas in Sweden by population, most populous city of Sweden, as well as the List of urban areas in the Nordic countries, largest urban area in the Nordic countries. Approximately ...
, five buses operated in
Madrid Madrid ( ; ) is the capital and List of largest cities in Spain, most populous municipality of Spain. It has almost 3.5 million inhabitants and a Madrid metropolitan area, metropolitan area population of approximately 7 million. It i ...
, three in
La Spezia La Spezia (, or ; ; , in the local ) is the capital city of the province of La Spezia and is located at the head of the Gulf of La Spezia in the southern part of the Liguria region of Italy. La Spezia is the second-largest city in the Liguria ...
, and one in Brazil. In Brazil, the first Scania ED95 bus with a modified diesel engine was introduced as a trial in São Paulo city in December 2007, and since November 2009, two ED95 buses were in regular service. The Brazilian trial project ran for three years and performance and emissions were monitored by the National Reference Center on Biomass (CENBIO- ) at the Universidade de São Paulo. In November 2010, the municipal government of
São Paulo São Paulo (; ; Portuguese for 'Paul the Apostle, Saint Paul') is the capital of the São Paulo (state), state of São Paulo, as well as the List of cities in Brazil by population, most populous city in Brazil, the List of largest cities in the ...
city signed an agreement with UNICA, Cosan, Scania and ''Viação Metropolitana'', a local bus operator, to introduced a fleet of 50 ethanol-powered ED95 buses by May 2011. Scania manufactures the bus engine and chassis in its plant located in
São Bernardo do Campo São Bernardo do Campo () is a Brazilian Municipalities of Brazil, municipality in the state of São Paulo. It is part of the Metropolitan Region of São Paulo. The population is 810,729 (2022 census) in an area of . According to 2021 data from ...
, São Paulo, using the same technology and fuel as the ED95 buses already operating in
Stockholm Stockholm (; ) is the Capital city, capital and List of urban areas in Sweden by population, most populous city of Sweden, as well as the List of urban areas in the Nordic countries, largest urban area in the Nordic countries. Approximately ...
. The bus body is a Brazilian CAIO. The first ethanol-powered buses were delivered in May 2011, and the 50 buses will start regular service in June 2011 in the southern region of São Paulo. The 50 ED95 buses had a cost of R$ 20 million () and due to the higher cost of the ED95 fuel and the lower energy content of ethanol as compared to diesel, one of the firms participating in the cooperation agreement, Raísen (a joint venture between
Royal Dutch Shell Shell plc is a British multinational oil and gas company, headquartered in London, England. Shell is a public limited company with a primary listing on the London Stock Exchange (LSE) and secondary listings on Euronext Amsterdam and the New ...
and Cosan), supplies the fuel to the municipality at 70% of the market price of regular diesel.


E100

E100 is pure ethanol fuel. Straight hydrous ethanol as an automotive fuel has been widely used in Brazil since the late 1970s for neat ethanol vehicles and more recently for flexible-fuel vehicles. The ethanol fuel used in Brazil is distilled close to the
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 ...
mixture of 95.63%
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 4.37% water (by weight) which is approximately 3.5% water by volume. The azeotrope is the highest concentration of ethanol that can be achieved by simple
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 ...
. The maximum water concentration according to the Agência Nacional do Petróleo (ANP) specification is 4.9 vol.% (approximately 6.1 weight%) The E nomenclature is not adopted in Brazil, but hydrated ethanol can be tagged as E100, meaning it does not have any gasoline, because the water content is not an additive, but rather a residue from the distillation process. However, straight hydrous ethanol is also called E95 by some authors. The first commercial vehicle capable of running on pure ethanol was the
Ford Model T The Ford Model T is an automobile that was produced by the Ford Motor Company from October 1, 1908, to May 26, 1927. It is generally regarded as the first mass-affordable automobile, which made car travel available to middle-class Americans. Th ...
, produced from 1908 through 1927. It was fitted with a
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 ...
with adjustable jetting, allowing use of gasoline or ethanol, or a combination of both. At that time, other car manufacturers also provided engines for ethanol fuel use. Thereafter, and as a response to the
1973 Events January * January 1 – The United Kingdom, the Republic of Ireland and Denmark 1973 enlargement of the European Communities, enter the European Economic Community, which later becomes the European Union. * January 14 - The 16-0 19 ...
and 1979 energy crises, the first modern vehicle capable of running with pure hydrous ethanol (E100) was launched in the Brazilian market, the
Fiat 147 The Fiat 147 was a three-door hatchback subcompact car produced by Fiat in the Brazilian state of Minas Gerais from autumn 1976 until 1987, when it was replaced by the Fiat Uno. It was the Brazilian variant of the Fiat 127. Some were also buil ...
, after testing with several prototypes developed by the Brazilian subsidiaries of
Fiat Fiat Automobiles S.p.A., commonly known as simply Fiat ( , ; ), is an Italian automobile manufacturer. It became a part of Fiat Chrysler Automobiles in 2014 and, in 2021, became a subsidiary of Stellantis through its Italian division, Stellant ...
,
Volkswagen Volkswagen (VW; )English: , . is a German automotive industry, automobile manufacturer based in Wolfsburg, Lower Saxony, Germany. Established in 1937 by German Labour Front, The German Labour Front, it was revitalized into the global brand it ...
,
General Motors General Motors Company (GM) is an American Multinational corporation, multinational Automotive industry, automotive manufacturing company headquartered in Detroit, Michigan, United States. The company is most known for owning and manufacturing f ...
and Ford. , there were 1.1 million neat ethanol vehicles still in use in Brazil. Since 2003, Brazilian newer flex-fuel vehicles are capable of running on pure hydrous ethanol (E100) or blended with any combination of E20 to E27.5 gasoline Print edition No. 1941 (a mixture made with anhydrous ethanol), the national mandatory blend. , there were 17.1 million flexible-fuel vehicles running on Brazilian roads. E100 imposes a limitation on normal vehicle operation, as ethanol's lower evaporative pressure (as compared to gasoline) causes problems when cold starting the engine at temperatures below . For this reason, both pure ethanol and E100 flex-fuel vehicles are built with an additional small gasoline reservoir inside the engine compartment to help in starting the engine when cold by initially injecting gasoline. Once started, the engine is then switched back to ethanol. An improved flex-fuel engine generation was developed to eliminate the need for the secondary gas tank by warming the ethanol fuel during starting, Ano 2, No. 3 (every article is presented in both English and Portuguese) and allowing them to start at temperatures as low as , the lowest temperature expected anywhere in the Brazilian territory. The Polo E-Flex, launched in March 2009, was the first flex-fuel model without an auxiliary tank for cold start. The warming system, called Flex Start, was developed by Robert Bosch GmbH. Swedish carmakers have developed ethanol-only capable engines for the new Saab Aero X BioPower 100 Concept E100, with a V6 engine which is fuelled entirely by E100 bioethanol, and the limited edition of the Koenigsegg CCXR, a version of the CCX converted to use E85 or E100, as well as standard 98-octane gasoline, and currently the fastest and most powerful flex-fuel vehicle with its twin-
supercharged 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. It is a form of forced induction that is mechanically powered (usually by ...
V8 producing 1018 hp when running on biofuel, as compared to 806 hp on 91-
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 ...
unleaded gasoline. The higher
fuel efficiency Fuel efficiency (or fuel economy) is a form of thermal efficiency, meaning the ratio of effort to result of a process that converts chemical energy, chemical potential energy contained in a carrier (fuel) into kinetic energy or Mechanical work, w ...
of E100 (compared to methanol) in high performance race cars resulted in Indianapolis 500 races in 2007 and 2008 being run on 100% fuel-grade ethanol.


Use limitations


Modifications to engines

The use of ethanol blends in conventional gasoline vehicles is restricted to low mixtures, as ethanol-gasoline is corrosive and can degrade some of the materials in the engine and fuel system. Also, the engine has to be adjusted for 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 ...
as compared to a pure gasoline engine to take advantage of ethanol's higher oxygen content, thus allowing an improvement in
fuel efficiency Fuel efficiency (or fuel economy) is a form of thermal efficiency, meaning the ratio of effort to result of a process that converts chemical energy, chemical potential energy contained in a carrier (fuel) into kinetic energy or Mechanical work, w ...
and a reduction of tailpipe emissions. The following table shows the required modifications to gasoline engines to run smoothly and without degrading any materials. This information is based on the modifications made by the Brazilian automotive industry at the beginning of the ethanol program in that country in the late 1970s, and reflects the experience of Volkswagen do Brasil. Disadvantages to ethanol fuel blends when used in engines designed exclusively for gasoline include lowered fuel mileage, metal corrosion, deterioration of plastic and rubber fuel system components, clogged fuel systems, fuel injectors, and carburetors, delamination of composite fuel tanks, varnish buildup on engine parts, damaged or destroyed internal engine components, water absorption, fuel phase separation, and shortened fuel storage life.''Is fuel with an increased level of ethanol a problem for small gas engines?'', Tools & Power Equipment, Consumer Reports, 24 June 2009Vatalaro, Michael,
A Serious Problem - A Corny Solution
', Boat US Magazine, (July 2006)
Maloney, William,

', retrieved 8 August 2011
Many major auto, marine, motorcycle, lawn equipment, generator, and other internal combustion engine manufacturers have issued warnings and precautions about the use of ethanol-blended gasolines of any type in their engines, and the
Federal Aviation Administration The Federal Aviation Administration (FAA) is a Federal government of the United States, U.S. federal government agency within the United States Department of Transportation, U.S. Department of Transportation that regulates civil aviation in t ...
and major aviation engine manufacturers have prohibited the use of automotive gasolines blended with ethanol in light aircraft due to safety issues from fuel system and engine damage.


Other disadvantages

Combustion of ethanol gives some
acetaldehyde Acetaldehyde (IUPAC systematic name ethanal) is an organic compound, organic chemical compound with the chemical formula, formula , sometimes abbreviated as . It is a colorless liquid or gas, boiling near room temperature. It is one of the most ...
, which is an irritant. Ethanol is not miscible with gasoline at low temperatures, e.g. in cold regions of the planet. It is also leads to deposits.


See also

* Butanol fuel * Ethanol fuel * Ethanol fuel energy balance * Ethanol fuel in Brazil * Biofuel in Sweden * Ethanol fuel in the United States * Food vs. fuel * Indirect land use change impacts of biofuels * List of flexible-fuel vehicles by car manufacturer * List of gasoline additives


Notes


References


External links


2011 NACS Annual Fuels Report
{{Authority control Ethanol fuel Petroleum products