What oil does the car door lock use if it is not flexible?

You can't use lubricating oil when the car door lock is inflexible, because the dusty lubricating oil has a certain adsorption effect, which will make the lock more inflexible. You can use pencil foam.

All mechanical locks will be difficult to insert or remove the key after a period of time. In this case, you can't lubricate the door with oil. Using oil will make the door unable to open, which is counterproductive. You should use a pencil to grind the key several times or blow pencil foam into the lock hole to lubricate the key. The lock will be more flexible and easy to use.