I could make fun of this as being over the edge but then, you'd make fun of me - my 500SL doesn't leave tha garage unless its bone dry out and no forecast of rain for two days (Houston) LOL

That being said, in my other cars, I just use some (gasp!) dishwashing soap... you gotta have something that will cut the road oil that flies up.

It may affect the wax job a little but if you're using your washers that much you're probably waxing pretty often anyway aren't you?

Kevin