I guess you're asking because you have a gasoline engine in your tow vehicle. If you have a diesel engine then use the truck pumps at travel centers and truck stops where canopies are high enough for the big rigs.
My previous truck had a 8.0 liter gas V10 engine that averaged 6 MPG when towing. On long road trips I'd have to make stops for gas a lot. Generally speaking almost all gas stations along the interstate highway system will have a canopy tall enough for your fifth wheel to fit under. Of the ones I encountered that were too low for my Wildcat they all had the height of the canopy marked.
There are still some older stations along state and county roads that have low canopies. From what I've seen most of the low canopies are obviously too low for the fifth wheel. If you are in doubt have whoever is traveling with you spot you as you slowly drive under the canopy.
Look for travel centers to gas up, I've yet to see one that didn't have a high canopy. Also when we traveled along the interstates I would only fuel up at exits that had more than one station. I always looked for stations that had easy in and easy out access.
Bob and Joyce
2013 CC Silverback 29RL
2010 Ford F250 XL Crew Cab 6.4 liter diesel
ATU Local 788