汽车燃油经济性（Fuel economy in automobiles，油耗）是汽车在保证动力性的基础上，以尽可能少的燃油消耗行驶的能力。日语习称燃费，即燃料消费之意，指机动车辆使用单位容量燃料（汽油、轻油等）可行走的距离，也可以说是一定距离下耗费多少燃料才能完成的一项指标。其数值会因为使用的燃料、胎压、路面状况、引擎油种类、承载重量、行驶方式等产生变化。

燃油经济性通常用一定运行工况下汽车行驶百公里的燃油消耗量或一定燃油量使汽车行驶的里程来衡量。

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 volume of fuel to travel a distance, or the distance travelled per unit volume of fuel consumed. Since fuel consumption of vehicles is a significant factor in air pollution, and since 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 fuel is required to overcome various losses (wind resistance, tire drag, and others) in propelling the vehicle, and in 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 fuel and kinetic energy of the vehicle. Driver behavior can affect fuel economy; maneuvers such as sudden acceleration and heavy braking waste energy.