Working on the wife’s 2018 F150. With the aluminum body I don’t fluid film it but I do want to hit the frame rails and such every couple years. When new I hit it with amsoil HDMP. It’s working OK but time for a refresh. Anyways, the frame seems to have this baked on mud splatter. Hasn’t come off in two years of car washes, doesn’t rinse off and doesnt come off with a brush or with mild hand rubbing. Feels smooth not like there is anything stuck on there. Will it be fine to coat over this with HDMP or will it significantly reduce protection? Any suggestions to wash it off? It’s almost like it imbedded in the initial coat two years ago even though it would have been more than enough time to dry before exposure…
