Since you have a Gas Motorhome The truck stop diesel lanes dont apply. Good news is you can use any gas station you can fit! No station will refuse to sell you 80 gallons! Your credit card transaction on "pay at the pump" may be limited however to a certain amount for the stations and card concern over stolen cards. Almost all cards will generally allow you Two transactions (swipe once fill and swipe again to finish) the Third time may not be approved ,so just use a second card.You can also go in and prepay/ authorize using a card or cash.
In my opinion not filling up unless traveling is not a good practice. your tank should be full while sitting to lessen moisture accumulation in the tank. Like many others we try to fill up near the end of the day before setting up.Since i use diesel my station choices are different but using a easy access busy station lessens the bad gas concern. Being in the trucking business and knowing a few drivers, all gas comes from the same refinery tanks so I don't really care about the" brand"