gas at truck stops

The other thing to think about is your credit card, if you use one at the pump. When you first insert your card, a predetermined amount is charged to your account to "hold" the funds. Usually in auto lanes, that is anywhere from $25 to $75. Then when you complete your actual purchase, the true amount is billed, and the remainder (if any) is freed up on your card for other uses. The kicker is how long it takes the station to "settle" the transaction - it can be very soon, overnight, or several days. Not too much of an issue with normal gas fills. But if you go to the trucker lanes, your initial amount could be as high as $500. And if your bill is only $75, you run the risk of not being able to use the remaining $425 for a number of days. If you hit a few stations that are slow to settle, you can exceed your credit limit, and your card will stop working for a while.
So if you plan to use a card at a pump, make sure it has a high limit!