On the subject of dishwashing liquids - mentioned by defibvt - I've read most are very harsh and will, at the least, remove wax. Only one supposedly mild enough to use for carwashing applications is Ivory.

I try to play it safe & use the carwashing concentrate put out by ArmorAll .. just haven't yet tried the stuff put out by Meguiar's but have no doubt it's as good as or better than the ArmorAll.

HTH :-)