Posted: Mar 29 2011 at 3:49pm | IP Logged

As a retired chemist, I have more negatives than positive views of undercoating.  My real problem is that as it ages, it can crack, blister and/or bubble, all of which allow salt and water to get UNDERNEATH the undercoating where it stays and really causes rust.

I spray underneath my Frontier with a light machine oil in the autumn and then once a week or so in the winter, I hose off the frame and the underside with clear water.  Been doing this for decades now and have had no real rust.  I live in central PA where the roads are snowy and quite salty!