Your car is a giant box of information that you need to keep sorted for one reason or another: year, make, model, last oil change, next oil change, engine size . . . Keep those details straight by adding your car to your phone's contact list.
As reddit user SithLard points out, your contacts app (usually) has a notes section where you can add any special info you want. You can use this section to store anything about your car you need to know but aren't likely to remember such as insurance information, or what type of oil your car takes. If you're a heavy note-taker, you could use your notes app of choice, but saving it as a contact is an option everyone can use.