Will washing the bottom of a car ruin it?

Washing the bottom of a car will not ruin it. In fact, it is recommended that you wash the bottom of your car regularly to remove dirt, salt, and other corrosive materials that can damage the undercarriage. You can wash the bottom of your car by using a hose with a nozzle, a pressure washer, or a car wash brush. Be sure to use a mild detergent and rinse the undercarriage thoroughly with water.