So how true is this? According to an article that I read, automatic car washes can be safer for your car's finish than washing your car yourself because do-it-yourselfers sometimes don't use enough water to safely remove dirt; or they wash the car in direct sunlight -- which can burn spots in the paint. Or they use the wrong type of soap -- such as dishwashing detergent, which removes protective wax and leaves a chalky residue on the finish. Or any one of several common mistakes can end up doing more harm than good.
To know more, click this LINK.