Not that anybody is wrong, but the side of that motorhome is a gel coat. When it's faded, it's faded. You can buff it, you can do the Zep, you can do all of these "remedies" to get rid of the ghost images. But, nothing easy is going to make it go away completely, and more important, permanently.
Being a painter for right at 40 years, I know what the powdered cleansers will do to the sidewalls, and that's scratch it, and that's not a good thing. The Zep treatment is an indoor product, and I know people have used it for a few years now with good results for that time. Not me, it is intended for indoor use. When I take the stripes off of my 2003 Flair, I'm going to wet sand with 1000 grit then 1500 grit wet or dry sandpaper (and don't forget to add a few drops of dish soap liquid to the water to help keep the paper clean and from clogging). Then I'll buff it back out with 3M polishing compound. And then apply a good wax of your choice. I like Meguiars, and Mother's products, but that's just from my painting experience. My flame suit is on, flame on y'all.....
Tank Thomas, USAF Ret.
There are no secrets to success. It's the result of preparation, hard work and learning from mistakes.