Most automobiles in use today are propelled by an internal combustion engine

The weight of a car influences fuel consumption and performance, with more weight resulting in increased fuel consumption and decreased performance. According to a research conducted by Julian Allwood of the University of Cambridge, global energy use could be heavily reduced by using lighter cars, and an average weight of 500 kg has been said to be well achievable.[24]
In some competitions such as the Shell Eco Marathon, average car weights of 45 kg have also been achieved.[25][26] These cars are only single-seaters (still falling within the definition of a car, although 4-seater cars are more common), but it nevertheless demonstrates the huge degree in which car weights can still be reduced, and the subsequent lower fuel use (i.e. up to a fuel use of 2560 km/l).[27]
Seating and body style

See also: Car body style
Most cars are designed to carry multiple occupants, often with four or five seats. Larger cars can often carry six, seven or more occupants depending in the internal arrange of seats. Sports cars are often designed with only two seats, and very occasionally three seats. The differing needs for passenger capacity and their luggage has resulted in a large variety of body styles to suit personal requirements such as the sedan/saloon, hatchback, station wagon/estate and Multi-Purpose Vehicle/Minivan.
Fuel and propulsion technologies



The Nissan Leaf is an all-electric car launched in December 2010
See also: Alternative fuel vehicle
Most automobiles in use today are propelled by an internal combustion engine, fueled by deflagration of gasoline (also known as petrol) or diesel. Both fuels are known to cause air pollution and are also blamed for contributing to climate change and global warming.[28] Rapidly increasing oil prices, concerns about oil dependence, tightening environmental laws and restrictions on greenhouse gas emissions are propelling work on alternative power systems for automobiles. Efforts to improve or replace existing technologies include the development of hybrid vehicles, plug-in electric vehicles and hydrogen vehicles. Vehicles using alternative fuels such as ethanol flexible-fuel vehicles and natural gas vehicles are also gaining popularity in some countries