fuel economy comparison

The fuel economy or fuel efficiency of an automobile relates to the distance traveled by a vehicle and the amount of fuel consumed. It can be expressed in terms of the volume of fuel to travel a given distance, such as in or litres per 100 kilometres (L/100 km), or through its inverse, the distance traveled per unit volume of fuel consumed, as in kilometres per litre (km/L) or miles per gallon (mpg). Since fuel economy of vehicles is a significant factor in air pollution, the importation of motor fuel can be a large part of a nation's foreign trade and consumers frequently undervalue fuel efficiency, many countries impose requirements for fuel economy.
Different methods 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) encountered while propelling the vehicle, and in providing power to vehicle systems such as ignition or air conditioning. Various strategies can be employed to reduce losses at each of the conversions between the chemical energy in the fuel and the kinetic energy of the vehicle. Driver behavior can affect fuel economy; maneuvers such as sudden acceleration and heavy braking waste energy.
Electric cars use kilowatt-hours of electricity per 100 kilometres (kWh/100km); in the U.S., an equivalence measure, such as miles per gallon gasoline equivalent (US gallon) has been created to attempt to compare them.

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