It is a well known fact that most Flying J Truck Stops are RV-friendly! Many of them have a separate area for overnight RV parking away from the semi trucks. Some don’t!
I’ve read from others who have done so that you can still go on the trucker’s side but they try to follow the truckers' rules if they do
: Don't go into the truckers parking area with your headlights on after dark (use your parking lights); dont take a pull-through site if you don't need it; stay between the parking lines; don't push out your slides; and use common sense and courtesy.
Conversely, I’ve also read that some truckers (rare) aren’t especially happy with an RV taking up one of their spots (some driver’s tend to be territorial). Some complaints have included: Has had RV vandalized; connecting pins removed from toad tow bars; and safety cables cut. So it’s best to check out your rv/connections/etc anytime you overnight park *anywhere* just to be safe.
If you use the truck stops to stay overnight, by all means fill your tank, get propane, eat a meal, or buy something in the convenience store