All things considered, we all wipe down the car after we wash it, right? Why do we wipe it down after a wash? To prevent spotting. What causes the spots? Dirt (Cl, K, some Na, etc) in the water (well or city). Same idea with rain, there is dirt in it. So if ya just washes the car, then it rains, I personally think it'd be fine to wipe her down. If it has sit out for awhile, and accumulated dust on it, then wash it. Just my $.02
