I had an 82 escort GT that had been originally bought in Illinois... it had that injected ziebart treatment and the parts that were injected didn't seem to have much rust. The wheel wells were another story - i noticed one day while replacing the rear brakes that I could not only see, but reach in and touch the passenger side rear speaker's magnet through a big rust crack in the fender well.

I have to assume that when they did the injecting thing they also did the standard undercoating thing, so the synopsis would be injection worked, undercoating kinda didn't work. at least not for 15+ years.

I had no idea what ziebart or even "rustproofing" were, being from the west coast.. had to ask someone "why are there all of these little yellow plugs in the door jams that say ziebart??" <img src="/forums/images/graemlins/kewl.gif" alt="" />