Liquefied petroleum gas (LPG), also called LP gas, any of several liquid mixtures of the volatile hydrocarbons propene, propane, butene, and butane.It was used as early as 1860 for a portable fuel source, and its production and consumption for both domestic and industrial use have expanded ever since. LPG is better for the environment as it is a cleaner-burning fuel that gives off 14% fewer CO2 emissions than petrol cars and 10% fewer than diesels. It also produces 50% less nitrogen oxides than petrol and 20% less than diesel.