Propane, also known as liquefied petroleum gas (LPG) or propane autogas, has been used worldwide as a vehicle fuel for decades. It is stored as a liquid, and propane fueling infrastructure is widespread. Propane has a high octane rating, making it an excellent choice for spark-ignited internal combustion engines. This energy source is produced as a by-product of natural gas processing and crude oil refining.
There are two types of propane vehicles: dedicated and bi-fuel. Dedicated propane vehicles are designed to run only on propane, while bi-fuel propane vehicles have two separate fueling systems that enable the vehicle to use either propane or gasoline.
Interest in propane as an alternative transportation fuel stems from its domestic availability, high-energy density, clean-burning qualities, and relatively low cost. It is the world’s third most common transportation fuel, behind gasoline and diesel, and is considered an alternative fuel under the Energy Policy Act of 1992.
Propane vehicles are available from original equipment manufacturers (OEMs) or via a conversion. According to the Propane Education & Research Council, there are nearly 200,000 on-road propane vehicles with certified fuel systems in the United States. Many are used in fleet applications, such as school buses, shuttles, and police vehicles. The availability of new light- and medium-duty propane vehicles has surged in recent years, especially for fleet use. A propane vehicle’s power, acceleration, and cruising speed are similar to those of conventionally fueled vehicles.
Propane autogas is produced domestically, so using it increases the country’s national security. This fuel has been used for awhile, so there is already a great foundation of accessible propane vehicles and infrastructure. Propane at primary infrastructure sites (those that frequently provide fuel to vehicles) typically costs less per gallon than gasoline and offers a comparable driving range to conventional fuel. The fuels high octane rating, combined with its low-carbon and low oil-contamination characteristics, has resulted in improved engine life compared to conventional gasoline engines, which is one of the biggest attractions for fleets. Propane vehicles emit less GHGs than conventional engines and present no threat to soil, surface water, or groundwater.
Propane vehicles require a significant investment because their purchase price can be thousands of dollars more than comparable conventional vehicles. The vehicles have a slightly lower fuel economy than conventional gasoline and produce equivalent amounts of tailpipe emissions.