There's nothing worse than a dirty car, it looks more lived-in than a 100-year-old house. fast food and drinks, kids with sticky candy, and pets also do their fair share toward making your car's interior — be it leather, cloth, or carpet — look beaten and worn. By maintaining the appearance of the vehicle inside as well as out, you retain the value of the car, which will help you when it's time to trade it in or sell it..