[olrocker]

The “black tar” that many companies used to use in the 1970s and 80s (Tuff Kote Dynol, Mickey’s, AutoArmor, etc) actually can seal in moisture and dirt if it’s not applied correctly. These old fashioned rustproofing made things actually worse, forcing the rust to develop from the inside out.

Check your door jams. See any plastic caps in them? That’s where they drilled into the jams to squirt rust proofing tar in between the body and seams.

As stated before lanolin-based prices are the best option today. I recommend Fluid Film.