It's my understanding the maintenance plan transfers with the car upon a sale. It's associated with the car in Porsche's records by VIN number. I imagine Carmax will assign a value to it when they make you an offer just like any other option. In the end, there's probably no way to know what you're getting for the maintenance plan over and above what you would've gotten without it. I think that's true no matter who you sell the car to.I'm thinking about selling my 2018 718 Cayman S and probably to Carmax. I purchased a 2-year 20k-mile prepaid maintenance plan when I purchased my car new for $920 and have not had a 2-year service yet. Is there a way to recoup the cost of the maintenance plan somehow? Can I get it refunded from Porsche NA or the dealer? Or perhaps transfer to another party?