It is the UV that does rubber in. You what to find something that has a lot of UV blocker in it. I have used Meguiar's M5716SP Marine/RV Vinyl & Rubber Cleaner & Protectant in the past; https://www.amazon.com/Meguiars-Marine- ... B0000AY4YJ
. 303 products are also good for this purpose ; https://www.amazon.com/303-vinyl-protec ... 20Products
. Do not use interior UV protection products for the outside rubber parts. Most of the interior stuff is water based, while the exterior UV protection stuff is oil based. On the outside, the water based protection will wash off.
I pour the liquid into a small dish or cup, after shaking the spray bottle, and apply the liquid to the rubber with a small foam painting brush. That way I have a lot better control of where the liquid is going. Spraying this stuff on just makes a mess all over the place. By bushing the stuff on, I can get nice even coverage of the rubber. I leave it on over night and then wipe or buff the next day as most of it will be gone and the rubber parts will get maxim amount of the product soaked in. The foam paint bushes are cheap at the hardware store and work very well for this application.