Fuel and propulsion technologies

According to the European Environment Agency, the transport sector is a major contributor to air pollution, noise pollution and climate change.

Most cars in use in the 2010s run on gasoline burnt in an internal combustion engine (ICE). The International Organization of Motor Vehicle Manufacturers says that, in countries that mandate low sulfur gasoline, gasoline-fuelled cars built to late 2010s standards (such as Euro-6) emit very little local air pollution. Some cities ban older gasoline-fuelled cars and some countries plan to ban sales in future. However some environmental groups say this phase-out of fossil fuel vehicles must be brought forward to limit climate change. Production of gasoline fueled cars peaked in 2017.

Other hydrocarbon fossil fuels also burnt by deflagration (rather than detonation) in ICE cars include diesel, Autogas and CNG. Removal of fossil fuel subsidies, concerns about oil dependence, tightening environmental laws and restrictions on greenhouse gas emissions are propelling work on alternative power systems for cars. This includes hybrid vehicles, plug-in electric vehicles and hydrogen vehicles. 2.1 million light electric vehicles (of all types but mainly cars) were sold in 2018, over half in China: this was an increase of 64% on the previous year, giving a global total on the road of 5.4 million. Vehicles using alternative fuels such as ethanol flexible-fuel vehicles and natural gas vehiclesclarification needed are also gaining popularity in some countries.citation needed Cars for racing or speed records have sometimes employed jet or rocket engines, but these are impractical for common use.

Oil consumption has increased rapidly in the 20th and 21st centuries because there are more cars; the 1985–2003 oil glut even fuelled the sales of low-economy vehicles in OECD countries. The BRIC countries are adding to this consumption.