Autogas is the name applied to Liquid Petroleum Gas when used as a vehicle fuel. The same gas that is often used in rural areas for cooking and central heating can be used to power vehicles. There is nothing new about vehicles powered by gas. some of the earliest stationery internal combustion engines were fuelled by gas. During the second world war vehicles could be seen with a large box shaped balloon on the roof containing coal gas, or town gas as it was often called, but it is true to say that, during the post war years, the ready availability of petrol reduced the need for gas fuelling. Happily, nowadays the gas technology does not rely on a giant balloon on the roof! The gas is now stored under pressure in liquid form in purpose made tanks. At room temperature and atmospheric pressure Autogas is in a gaseous state, changing to liquid when subjected to pressure. Being in a liquid state under low pressures gives Autogas an advantage over natural gas which will only turn to a liquid at extremely low temperatures. Therefore with Autogas more fuel can be stored for the same weight and volume than with natural gas.
In many countries LPG for automotive use is a mixture of propane and butane gases, usually in equal proportions, although some countries, depending on the ambient temperature, use varying ratios of propane and butane at different times of the year. In the UK propane only is used as the market place for Autogas is small when compared with industrial and domestic uses. The supply companies do not wish to send separate tankers out to industrial, domestic and Autogas users. This may change in the UK when the use of Autogas as a vehicle fuel becomes more widespread.