Add Years to the Life of Your Car Car interiors and exteriors can take a real beating during the winter months. The build up of salt on the outside and sand and other debris inside will quickly dull finishes and leave carpets and upholstery looking worn. The key is to give your car a thorough washing after snow storms and sunny days of melting slush. Be sure to use a carwash that provides undercarriage washing. Using mats and vacuuming often will keep carpets looking new.