A natural gas vehicle (NGV) is an alternative fuel vehicle that uses compressed natural gas (CNG) as a cleaner alternative to other fossil fuels. Natural gas vehicles should not be confused with vehicles powered by propane (LPG), which is a fuel with a fundamentally different composition.
Worldwide there is +- 14.8 million natural gas vehicles (2011). Existing gasoline-powered vehicles may be converted to run on CNG . Diesel engines for heavy trucks and buses can also be converted to run on a blend of CNG and Diesel.
CNG must be stored in high pressure cylinders (3000psi to 3600psi operation pressure). These cylinders take up more space than gasoline or diesel tanks that can be molded in intricate shapes to store more fuel and use less on-vehicle space. CNG tanks are usually located in the vehicle's trunk or pickup bed, reducing the space available for other cargo.
CNG-powered vehicles are considered to be safer than gasoline-powered vehicles.
Autogas is the commonly used name for liquefied petroleum gas (LPG) when it is used as a fuel in internal combustion engines in vehicles as well as in stationary applications such as generators.
Autogas is widely used as a "green" fuel, as its use reduces CO2 exhaust emissions. The octane rating is between 90 and 110.
Autogas is the third most popular automotive fuel in the world, with approximately 16 million of 600 million passenger cars powered using the fuel. Approximately half of all AutoGas fueled passenger vehicles are in the five largest markets (in descending order): Turkey, South Korea, Poland, Italy, and Australia.