Car maintenance involves various aspects, including grease for components such as the oil door, hinge, and slide skylight track. Applying grease can reduce friction, prevent abnormal sounds, and ensure smooth operation. For example, greasing the hinge of a car door can make it open and close more smoothly without squeaking. When maintaining the skylight track, using the right grease can prevent sticking and ensure the skylight slides easily. White oil is often used for such maintenance work. Regular maintenance of these parts helps keep the car in good condition and enhances driving comfort and safety. It's important to choose the appropriate grease and perform maintenance regularly to avoid potential issues and ensure the longevity of the vehicle's components.