fuelefficiency

Fuel efficiency, in transportation, is the distance traveled per unit of fuel energy. It is commonly expressed as miles per gallon (mpg) in the United States, and liters per 100 kilometers (L/100km) in many other countries. For electric vehicles, energy efficiency is measured as kilowatt-hours per 100 kilometers or miles per kilowatt-hour, and some metrics use miles per gallon of gasoline-equivalent (MPGe) to enable comparison with gasoline vehicles.

Measuring fuel efficiency relies on standardized tests such as the U.S. Environmental Protection Agency (EPA) testing cycle, the European Union’s WLTP, or similar methods elsewhere. Real-world fuel economy often differs from laboratory results due to driving behavior, terrain, climate, vehicle load, and maintenance. Efficiency can be expressed as fuel consumption (L/100km, gal/100mi) or as distance per unit energy (mpg, miles per kWh).

Factors affecting efficiency include engine or motor efficiency, drivetrain losses, vehicle mass, rolling resistance, aerodynamic drag, tire selection, and auxiliary loads like air conditioning. Driving practices such as gentle acceleration, steady speeds, and minimizing idling improve economy. Hybrid and electric powertrains use regenerative braking and energy recycling to enhance efficiency.

Importance and applications: higher fuel efficiency reduces energy consumption, emissions, and operating costs. Automakers and regulators pursue efficiency through design choices, technology development, and efficiency standards to balance performance, cost, and environmental impact.