Car cover for the sun?

Thats a tough one. IMO it would be better with a tent cover that does not touch the car. Anything touching the car tends to hold in moisture and cause heat buildup. But then I am in Houston, TX.

Any cover at all will cut way, way down on sunlight damage. In Arizona sunlight, the cheapest ones last about 12-18 months, the best about 4 years before they start tearing (usually first around the rearview windows, so consider cutting holes there) or shedding lots of lint. Costco and Wal-mart can be a lot cheaper than anyone else for covers. The tie-downs won't work in high winds; only a draw string all the way around the bottom perimeter or a bunch of magnets will do that.

Get metalized window tint because even the lightest will block at least 95% of the UV. A dashboard mat will block most sunlight but is actually very porous, so I line mine with a layer of aluminize mylar (space blanket material, like window tint). Apply vinyl preservative anyway. Covering the seats with a white bedsheet also helps, especially if it's washed every few weeks in detergent containing brightners, which boost the SPF from about 5x-8x to 30x-50x.

Higher priced car covers made of Tyvek or Technalon are advertised for being able to block rain, and even though you can form a bag out of the material and hold a couple of gallons of water without leaking a drop, rain will wick right trough. The only waterproof covers are made of vinyl.

One of those blue tarps used for storm damaged house roofs.

Those cheap covers though, I once bought one at Wal Mart.It didn't even last a year. cuhulin

Found some on the Net made from acrylic..... but cost was $395