Worked with a friend of mine to detail out his 40yr old bass boat.  He has tows it with a diesel for the past ten years or so.  Many times with out the cover.  (likes to unload and go)  I had brought several Meguiar products over to try them out to see how they would work.  Even though he kept the boat wiped down and occasionally use cleaner the seats were in bad shape.  I was working with the DA on the outside, and he was using the M39 on the inside.  We were both blown away at how well it worked.