The solitary perfect protector for tires and plastic is shade
Next is silicone dielectric grease. No petroleum. But the stuff is costly and has to be applied something like twice a year. It really works. I used tons of it on rubber and stainless steel adel clamps sitting in the sun. Works on plastic electrical wiring, but cross link insulated wire is almost as good.
Go to the tropics. Observe bronzed ladies of advanced years. Their skin resembles a gator's.
Ultraviolet is a powerful ray. Even virus and bacteria surrender before it.