Dish soap is good for grease & grime, but seems to strip wax faster.
Car soap seems to prolong wax, but does a good job at lifting dirt from the paint.
I haven't used dish soap on a vehicle in years, come to think of it; haven't really got one grimy enough.
We use dish soap when we are going to buff a car because it does strip all off all the protective protection. Otherwise it just seems too harsh in most cases. The car wash products with wax do have a little residual paint protection that helps a little to resist stains and is easier on any protectant that is already there.
