Look for the Flying J truck stops to get fuel. Whenever I am traveling in the motorhome, I always use them for the following reasons:

1. They have specific islands for motorhomes/tow rigs with diesel that are pay at the pump
2. You can get a discount card for fuel at no charge(for the card, not the fuel)
3. All their truck stops are listed on their website along with fuel prices so you can plan where to stop and get fuel as well as know what to expect to pay before you leave.
4. They have separate areas for motorhomes/tow rigs that are away from the truck where you can park and sleep for as long as you wish at no charge.

I also have found them to be quite accommodating.