The fuel economy of an automobile is the fuel efficiency relationship between the distance traveled and the amount of fuel consumed by the vehicle. Consumption can be expressed in terms of the volume of fuel to travel a distance or the distance traveled per unit volume of fuel consumed.
Since fuel consumption of vehicles is a significant factor in air pollution, and since the importation of motor fuel can be a large part of a nation’s foreign trade, many countries impose requirements for fuel economy.
Different measurement cycles are used to approximate the actual performance of the vehicle. The energy in the fuel is required to overcome various losses (wind resistance, tire drag, and others) in propelling the vehicle and providing power to vehicle systems such as ignition or air conditioning.
Various measures can be taken to reduce losses at each of the conversions between chemical energy in the fuel and vehicle kinetic energy Driver behavior can affect fuel economy; maneuvers such as sudden acceleration and heavy braking waste energy.