I was curious to experiment with this as well. My region usually gets about 5 inches of rain a month, but we haven't had any measurable rain since I bought the car almost 3 months ago. I think we are currently 17 inches below normal for the year. I can't even wash my car. If you are seen using a water hose to clean your car, they fine you $100 on the spot. I've been keeping the car clean with a car duster and spray detailer. My car hasn't had a "bath" in 6 weeks.