Three of my four vehicles are black and I never wash them unless they get rained on or in some other way their paint gets damp. Since they're always under a roof, even at work, all I need is my California Car Brush.
Cleaning your car, however you do it, is good to do on a regular basis so that you can keep an eye on the condition of your car's body and paint job and keep a lookout for any new dings or scratches.
Karl
