I sold my then new 2006 Mustang almost 4 weeks ago, within 2 weeks, at asking price. The car was Ziebart rust proofed along with under body coating. At that time, the Mustang body was all metal. Anyway, after all the Wisconsin winter driving, up until 2021, with early 4 years of winter daily expressway driving , the car was clean. I had 4 Blizzak snow tires. The car was driven year round.
Our then new 2019 Ford Edge, was also Ziebart treated with underbody coating. Ziebart stickers on rear windows.