I might be able to clear up some of the confusion/misconceptions about propane. Propane is a type of Liquefied Petroleum Gas (LPG) along with Butane and Iso-butane. It is widely available throughout the US--mostly at gas stations but also at Propane suppliers and some convenience stores. "Vehicle Propane" is the same chemically as any other propane--like the kind you run your camp stove on--but you must have a way to get it into the vehicle fuel tank. Any gas station that sells propane can dispense propane into your vehicle fuel tank (via pressure increasing pump)--you just can't go to the hardware store and buy a cylinder for your barbeque and expect that you will somehow be able to pour it into your vehicle fuel tank. The State of Washington charges a substantial tax for diesel, gasoline and, yes, propane. If you have a propane powered vehicle, and purchase the special tax stamp thingie, you pay an annual tax instead of a per gallon tax. However this only works if you are able to find a dealer (few and far between) that understands the tax stamp thingie. Most local gas stations don't so you will have to pay full price. But propane is propane whether you buy "regular" propane or "vehicle" propane. Now here is where it gets interesting. Propane is a bi product of manufacturing gasoline. So the supply is gasoline driven. Propane is mostly used for heating. Gasoline sales drop in the cold months so propane costs go up. In the summer when gasoline demand increases, therefore so does the propane supply and so the propane price goes down. Soooo--combined with propane being 120 octane--it could be a great tow vehicle fuel. In the summer it is usually about $2.50 per gallon. It gets the same rough mileage as the same gasoline vehicle. You can have a system that allows the vehicle to run on propane or gasoline at the flip of a switch. It would be an ideal conversion for an older (carburated) vehicle. Have no idea about fuel injected vehicles.