can you wash a car cover?

I have a California Car Cover on two of my cars. The instructions that came with both covers said they can be washed in a large washer (think laundromat extra large style ). It also said to use a cleaner like "Simple Green" only. Do not machine dry. I cost me about $7 to do a cover. If you go on the car cover manufacturer's website they will probably tell you how to wash your cover. They all seem to have different requirements/recommendations.