Dressed or Undressed?
I recommend not dressing your RV tires, as it will strip the tires' rubber of their UV protection. I recently attended the 2016 FCOC rally in Yuma, AZ. where Michelin Tire experts gave a really good seminar of tire maintenance and use etc.
One question asked in several different ways was about tire dressing, using a solvent to clean and make your tires shine. The consistent answer from the experts was no, nothing, nada, soap and water only.
They said that most cleaners have petroleum as one of their ingredients and that will rot your tire. They have tested every, and I mean every as the ran off the names of most every major and secondary brand and then some, product and did not find any evidence that it will help the tires.
A test they recommend is that if you do use a cleaner product. Put it on wait about an hour or so then rub your finger over the tire wall of the tire. IS there any black or white or any kind of residue on your finger? If there is what you just rubbed off is either rubber, sun screen protection, ozone protection, or some other protection chemical that was built into the tire to protect it and you just removed it.