3M body shutz won't creep into the pinch welds like oil. I do this every other year just before winter. That squirter will shoot oil all the way to the front of the bed panels, putting a good coat inside where the rust really starts. I also squirt it into the doors, rockers, tailgate and fenders. You will have to wipe oil off some of the drain areas for a couple days but that's a lot better than having it rust to death. Make sure it's been dry out for a couple days before oiling, you don't want to trap water in there.