I'm sold on oil-based rustproofing. If they can fog it into body cavities, frame rails, etc...you can't go wrong. I wouldn't even consider Ziebart for rustproofing at this point. I might use them for bedliner or something.
So here's my car...I haven't washed it for months for some reason. Anyway...you can see where the Krown is leeching out of the panels. I think I had it sprayed almost a year ago.
Here you can see it coming out from behind the side marker...