We use a AAA credit card dedicated to fuel purchases only, swipe at the pump only authorized to recieve our 5% discount for the security and accounting. AAA has phoned me within seconds when we attempted to use the card outside our stated $ limits or geography. Good for them!
We do have an 80 gal reserve tank so with the trucks 34 gal we have 12 -1400 mi. between fueling when towing. When we do fuel, we do it where we wish, at the price we wish. The tank has paid for itself many times over in savings and convenience.