Ok, this is probably going to be a really dumb question and I believe my rookie-ness may show.
If you have your car/truck undercoated is it not going to get washed off if you go through one of those car washes with the under carridge wash, is it not going to get washed off?

 

Man it better not. that stuff is applied and is supposed to be a permanant barrier of preotection for the underside of the vehicle. If it comes off, take it back to whomever did the work and have it reapplied.

 

I pressure wash mine all the time and it hold on just fine. I use a self applied rubberized undercoat. I do re-apply it every couple years or so because of rock chips, but other then that it holds up just fine.