We have a 36 ft 5th wheel and have been pulling it for a little over 7 years. We normally stop at truck stops/RV Islands. We have the Pilot/Flying J card with the discounts so the price is normally the cheapest or close enough to it. We also stop at TA, Loves etc.
We solve the "going inside" problem with walkie-talkies. DW gets the pump number, goes inside with the credit card, gets the pump started and then calls me so I can start pumping. When the tank is full, I call into her, she signs the receipt and hurries out so I don't forget her.
As far as the fuel tax, it can be a pain but just have DW tell the person at the desk you are a private RV and they should know how to handle it. All in all, there are not that many states where you have to deal with that. The ones that do will normally show different prices for truck fuel and auto fuel.
In the truck lanes, there is normally a line to show you where to pull ahead to after you have fueled and waiting for DW. That lets a truck pull in behind you and start fueling after you have finished. As others has said, if you are going inside to eat, shop or use the restroom, find a parking spot.
About the only comments I have had from truckers start with "I have an RV too". Will some give you the evil eye, maybe, but so will some car drivers if you pull into the auto lanes. Just use common sense and courtesy and all will be fine.
Ken and Sue Smith
'15 Silverado 3500 LT, DRW, D/A, Ice Silver
2007 Carriage Cameo 35KS3
2016 Coleman 235QB - Lantern
Indecision is the Key to Flexibility