I was talking to a buddy about this and it wasnt that clear what we figured out. This is more fun than anything. If i have to buy a permit $240.00 to burn propane in a truck that gets 10 mpg and propane is 00.70 a gallon cheaper than gas how many miles will i have to drive to pay for the permit? I know it will burn more propane per mile than it would gas but agin its just for fun and dosent really matter .