Interesting thread!
We're relatively new to 5th Wheeling, but have crossed the country from Seattle to Key West, so have seen a bunch of fuel stops. I'd love to have an aux tank, but so far haven't decided it's worth the grand or so investment. One day...
Meanwhile we're fueling once or twice a day on the road, and use a mix of truck stops and regular stations with Diesel. Our rig's "kind of" short - just 32' behind the truck, so maneuvering isn't usually a big problem. But the height of this 5'er is 13', so I'm hyper-sensitive to pump canopy heights, and have found lots of stations which don't have the 13'6" minimum that I'm willing to negotiate.
We do use truck stops wherever possible. But my experience is that MOST of 'em won't let you leave a card (even if you wanted to), but make you pre-pay, then pump. Since I'm wanting to fill my tank (my F250 only takes 30 gal from empty) what I do is estimate high and pay for a bit more than I need. When the charge goes through, the card gets credited with the difference between what you paid and what you pumped. You might give this a try. An equally annoying problem is the huge number of pumps that are limited to $75 or $80 at a time. These brain dead machines just stop pumping, and to get more fuel you have to "hang up and dial again". How stupid is that!?
Me: I'm getting closer and closer to installing a 50 gal aux tank, so I can stop worrying about this quite so much! Then I'll just pull into the truck stop and take 70 gal or so - who cares about a fill up if you're toting three days fuel?