I fuel up at the end of each day before I stop to camp. That way I can track my mileage, fuel consumption, generator usage, etc... I just end up doing two or more transactions with the same card, at whatever limit the fuel pumps are set to. I always choose Debit, and let my bank know when I head out on a trip.
One thing you can do if you choose to go inside, is to prepay for the fuel and then whatever you don't use will be refunded back to the card. That would guarantee a single transaction, but does mean you go into the store at least once.
I also use gasbuddy and try to find cheaper gas and then use google maps to determine which ones I can get into with my Motorhome and toad. Pilot, Flying J, Loves etc... typically are easier to get in and out of.
Michael & Angela Foret
North Central Florida
2019 Entegra Vision 31V