+MarkG Short answer - cost savings. Long answer - Propane is a lot less expensive than race fuel and has the advantage of greater octane ratings (104) so you can make serious HP with less fear of burning down. It is a gas at any temp above -44f, so if you go sledding and it's colder than that, no gas will come out of the tank. At really cold temps, the tank may have to be heated to deliver adequate fuel. In addition to having a turbo, a efficient propane engine will have greatly increased throttle response and 'crispiness' of the engine.