When on the highway I look for either a truck stop or one of the large gas stations that have lots of room at the pumps
Like others have posted most of the time I will fill while unhitched from the 5th wheel either after we finish setting up camp or before we leave to head to the next stop.
One time we needed fuel and had to pull into a little town and the only station was one of the small type from the 50's. My wife direct traffic around our 5th wheel because the rear end stuck out into the street. She said most people smiled and waved at her as they went by.