If you check what rental companies charge for gas when you pick up a car, they typically list something like $12/gallon here if you don't prepay, and something

If you check what rental companies charge for gas when you pick up a car, they typically list something like $12/gallon here if you don't prepay, and something like $5-7/gallon if you "buy the tank". This vs maybe $3-4/gal at the nearest station.