One would think that but debit cards are usually going to be cheaper. At virtually any retail outlet when the charge is going to be defined before the transaction starts it defaults to debit. When you pull that nozzle out they don't know how much gas you will pump and there is no way to get it back if you pump more than you have in the bank. That is why they will impound the total a pump will let you have until they get around to settling up, no matter what you pump.
