Propane, also known as liquefied petroleum gas (LPG or LP-gas) or autogas, has been used worldwide as a vehicle fuel for decades. Stored under pressure inside a tank, propane turns into a colorless, odorless liquid. As pressure is released, the liquid propane vaporizes and turns into gas that is used for combustion. An odorant, ethyl mercaptan, is added for leak detection.
Propane has a high octane rating and excellent properties for spark-ignited internal combustion engines. Propane is produced as a by-product of natural gas processing and crude oil refining. It accounts for about 2 percent of the energy used in the U.S. Uses include home and water heating, cooking and refrigerating food, clothes drying, powering farm and industrial equipment and drying corn. Rural areas that do not have natural gas service commonly rely on propane. The chemical industry uses propane as a raw material for making plastics and other compounds. Less than 2 percent of U.S. propane consumption is used for transportation fuel.
Propane is considered an alternative fuel under the Energy Policy Act of 1992. According to the Propane Education and Research Council, there are more than 270,000 on-road propane vehicles in the U.S. Many are used in fleet applications, such as police cars, shuttles and school buses.
The development of new, light- and medium-duty propane vehicles has surged in recent years for fleet use. Propane vehicles can either be conversions from gasoline vehicles or purchased from original equipment manufacturers.