Learned about a product from the travel trailer forum we belong to....it's called "303 Aerospace protectant" and has a SPF of 40. Can be used on rubber, tires, matte plastic, plastic windows. I put it on the VX tires and our trailer tires 2 weeks ago, doesn't have ANY stickiness at all so no dirt sticking to tire. These folks have used it for years, so I figure it can't hurt.....
http://www.303products.com/shop303/i...protectant.cfm