intrceptor....two recommendations....try "303 Aerospace Protectant is the most manufacturer recommended protectant by manufacturers of automotive, aviation and boating vinyl. 303 Aerospace Protectant protects any vinyl, rubber or plastic surface from the damaging effects of ultraviolet light. Regular use can prevent nearly 100% of UV fading and degradation!" according to the mfg.
also, I use Zaino z-16 tire gloss for tires and all rubber/vinyl exterior surfaces. the stuff is non-greasy and lasts thru multiple car washes....unlike silicone based products, it produces a satin, not glossy, waxy finish. I take my X to a manual car wash and blast the hell out the wheel and tire.....the water actually beads off the tire like it was waxed. Amazing stuff.
try both....hope they help. I am in a sunshine state too, but my car is garaged where I work and at home, but ya never know.....let me know how they work out.