Liquefied petroleum gas or liquid petroleum gas (LPG or LP gas), also referred to as simply propane or butane, are flammable mixtures of hydrocarbon gases used as fuel in heating appliances, cooking equipment, and vehicles.It is widely used alternative fuel. It has substantial reserves due to its dual origins from natural gas processing and crude oil refining. Liquefied Petrol Gas (LPG) powered passenger cars have about 10% lower tailpipe CO2 emission than comparable gasoline-powered cars. When compared to a diesel car, there is no significant CO2 emission reduction per km driven; however, LPG powered vehicles do have substantially lower NOx emissions than diesel-powered vehicles.