Hey man, think about the weathershield hd. Thats what im ordering for my car. I was told ( from the manufacturer ) that it repels dirt ( of course ) and water amoung many other things. It is also a tight fit, and comes specially fabricated for your car . The only thing is it's a little pricey. The cost for my e39 528i is around $405.00 . But as stated it is a specially fabricated cover for your car, and takes about 2 weeks to make. Check it out more at carcover usa.
I spend at least 2 hours a day cleaning my car