I have only been through a truck wash once. I believe they use an acid wash on tankers but they said it should not be used on the RV (due to clear coat?) so they did not - supposedly!
They did use some sort of wax in the rinse.
Did a pretty good job of getting the Canadian road salt off on a southbound winter trip, but cost me $60 so I only did it once!
Brian & Connie Mitchell
2005 Classic 30'
Hensley Arrow / Centramatics
2008 GMC Sierra SLT 2500HD,4x4,Crew Cab, Diesel, Leer cap.