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 theUniversity 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 forthfluing lower fuel use (i.e. up to a fuel use of 2560 km/l.^[27]