I But who wants the underside of their vehicle coated with grime?
Well...
when I was a kid my grandpa run a car repair shop. One of the services he offered, was undercoating for the winter. The stuff he sprayed was a mix of used motor oil, penetration oil, that sticky oil you use for chain saws, petroleum jelly and woolwax. He came up with this formula himself, after a lot of testing. After he was done, he drove the car over a dry dirt road "to bake it in" as he called it. It worked very well, but it was a mess.
Good memories though - he taught me al lot about cars and engines and I loved to be at his shop.
