I got suckered into the protective coating from the dealership when I purchased. My first F150 so at the time I figured what the hell, sure. Lots of road salt where I live. I later looked it and it appears all they did was take one of these spray cans and spray a few areas. Not comprehensive at all. So maybe I’ll go back and try this DIY approach later.Based on a very informative F150 Gen 14 thread long term test of undercoat products, I used about 4 cans of Amsoil Heavy Duty Metal Protectant to hand-spray every surface, crevice and hole for the bottom 10 inches of my Lightning.
It too a while on a sunny day 13 months ago. I had the truck up on ramps, 1st on end and then the other end. We have only a driveway (1930s house in an old inner suburb).
The overspray made me wear a woodworking respirator and goggles.
70% or so of the Amsoil went into the ends of the undercarriage because of the battery protection plates.
We can't prove a negative, but I'm glad I paid the $$, and glad I did the work myself. The Amsoil HD MP coat has dried to a very nice half-solid film and now a year later I see nothing I do not like, despite running the truck through a lot of different environments including layers of baked-on salt at the Bonneville Salt Flats.
As an added benefit he more than 90 minutes of this work, on a nice warm Fall day, made me learn the truck's underside thoroughly. And of course, this type of work when done myself vs. being delegated to the unknown 19-year old in the franchise's back shop does provide some certainty.