Propane:liquefied petroleum gas (LPG)

       Propane or liquefied petroleum gas (LPG) is a clean-burning fossil fuel that can be used to power internal combustion engines. LPG-fueled vehicles produce fewer toxic and smog-forming air pollutants. LPG is usually less expensive than gasoline, and most LPG used in U.S. comes from domestic sources.
No LPG-fueled light-duty passenger cars or trucks have been produced commercially in the U.S. since the 2004 model year, but gasoline and diesel vehicles can be retrofitted to run on LPG in addition to conventional fuel. The LPG is stored in high-pressure fuel tanks, so separate fuel systems are needed in vehicles powered by both LPG and a conventional fuel such as gasoline.

 Advantages:      

• Fewer toxic and smog-forming air pollutants
• 85% of LPG used in U.S. comes from domestic sources
• Less expensive than gasoline

 Disadvantages:

• No new passenger cars or trucks commercially available (vehicles can be retrofitted for LPG)
• Less readily available than gasoline & diesel
• Fewer miles on a tank of fuel