I always asked the manager at a Wal-Mart if it was alright to park overnight in his lot AFTER purchasing items we needed. Seemed to go alot smoother if he/she saw that we'd patronized their business.
I'd always try to ask where he/she preferred me to park to make sure I was out of the way of everyone. And let them know when I expected to leave.
Only once was I asked to leave, but it wasn't only trucks. The local police were asking everyone to leave this certain part of the lot for some reason. trucks, cars, rv's.......if I remember right, that was in Oregon.
Just a little advice though..........if your going thru Arnold Mo.......which is just south of St. Louis on I-55.........DON'T.........I repeat........DON'T even think of going in the Wal-Mart there if your in a straight truck......It's the most screwed up parking lot I've ever seen!! VERY difficult to get a straight truck in and out. Their firm believers of cement dividers and have most of the lot sectioned off in small squares. Easy for cars, nightmare for straight trucks!!!!!! beep, beep, beep, look out, I have to back up one more time so I can make the corner into the next section. Let's see, where the heck was that entrance/exit again???
How did it get way over there!! Wasn't that far when I drove in!! LOL