Progressive shifting is a technique for changing gears commonly practiced by drivers of

semi-trailer truck A semi-trailer truck (also known by a wide variety of other terms – see below) is the combination of a tractor unit and one or more semi-trailers to carry freight. A semi-trailer attaches to the tractor with a type of hitch called ...

s. It is meant to reduce

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 ...

consumption — something very important for drivers who travel several hundred miles each day. Progressive shifting is accomplished by changing gears upward as early as possible when accelerating while staying within the flat torque range. Each shift will go a little higher into the RPM until the vehicle is in its top gear at cruising speed. After each shift is completed, the

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 ...

and transmission should be operating at or near the lowest

rpm Revolutions per minute (abbreviated rpm, RPM, rev/min, r/min, or r⋅min−1) is a unit of rotational speed (or rotational frequency) for rotating machines. One revolution per minute is equivalent to hertz. Standards ISO 80000-3:2019 def ...

speeds recommended by the manufacturers of those parts. The fastest acceleration is achieved when the truck is receiving as close as possible to maximum power throughout the entire time it is accelerating. E.g. in a truck with a Caterpillar C15 engine, it is achieved by going all the way up to 1950RPM, then shifting to a gear that will put the engine at 1500RPM. In contrast, using progressive shifting, i.e. maintaining maximum

torque In physics and mechanics, torque is the rotational analogue of linear force. It is also referred to as the moment of force (also abbreviated to moment). The symbol for torque is typically \boldsymbol\tau, the lowercase Greek letter ''tau''. Wh ...

, the overall acceleration is slower but there is increased

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 lower wear of the engine due to lower RPM.

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* *{{cbignore Trucks