A car is something that is going to be sold on at some point, maybe a few months down the line or maybe 10 years later. With more and more personalised services built in there needs to be a simple straightforward 'do this when you sell' process detailed either in the handbook (if you have it) or in a menu on screen. It needs to be simple enough for your mum to use - think about all the people you have to support with (simple) tech issues. I also needs to either kill any linked online accounts or deregister itself as a linked device from them either automatically or indicate to you what they all are and how to do so manually.
Remember not every car will be traded in to a dealer (who you would hope would be able to do this as part of the selling on process) but you could be selling/buying it as a private sale.
Biting the hand that feeds IT
