Original sentence: Fuel economy in automobiles is the amount of fuel required to move the automobile over a given distance.While the fuel efficiency of petroleum engines has improved markedly in recent decades, (especially diesel engines that are now up to 45% efficient), this does not necessarily translate into better fuel economy, if larger and heavier vehicles are used, or if that efficiency is used to produce faster cars capable of higher rates of acceleration
Edited sentence: Fuel economy in automobiles refers to the amount of fuel required to move the automobile over a given distance.While the ability of petroleum engines to maximize the transformed chemical energy of the fuel (their fuel efficiency) has increased since the beginning of the automotive era, this has not necessarily translated into increased fuel economy, which is additionally affected by the mass, shape, and size of the car, and the goals of an automobile's designers, which may be to produce greater power and speed rather than greater economy and range