Propane, also known as liquefied petroleum gas (LPG) or liquefied natural gas (LNG), is the fuel of choice for many fleets. LNG has been used as a clean burning alternative vehicle fuel in thousands of trucks, buses, waste collection trucks, and other vehicles in the United States for more than 15 years. Propane as a gas has a high energy density, giving vehicles a sizeable driving range. Propane fueling infrastructure is also widespread
Today most propane vehicles are conversions from gasoline vehicles. Dedicated propane vehicles are designed to run only on propane; bi-fuel propane vehicles have two separate fueling systems that enable the vehicle to use either propane or gasoline.
Propane vehicle power, acceleration, and cruising speed are similar to those of gasoline-powered vehicles. The driving range for bi-fuel vehicles is comparable to that of gasoline vehicles. The range of dedicated gas-injection propane vehicles is generally less than gasoline vehicles because of the 25% lower energy content of propane and lower efficiency of gas-injection propane fuel systems. Extra storage tanks can increase range, but the additional weight displaces payload capacity. Liquid Propane Injection engines, introduced in 2006, promise to deliver fuel economy more comparable to gasoline systems.
Lower maintenance costs are a prime reason behind propane’s popularity for use in delivery trucks, taxis, and buses. Propane’s high octane rating (104 to 112 compared with 87 to 92 for gasoline) and low carbon and oil contamination characteristics have resulted in documented engine life of up to two times that of gasoline engines. Because the fuel mixture (propane and air) is completely gaseous, cold start problems associated with liquid fuel are eliminated.
Compared with vehicles fueled with conventional diesel and gasoline, propane vehicles can produce significantly lower amounts of harmful emissions. The use of domestic propane is also key to increasing U.S. energy security.