Logic says sell it. But if this involves sentimental value then instead of treating this with contempt and an air of superiority (which is how I read your tone), you could try to sound a little more sympathetic. Yes, it should be sold because no vehicle should sit that long and still be expected to run. Not to mention the cost of upkeep for it once the teenager starts driving it. No teenager needs repair bills on top of everything else. However as a family member did just die (you don't say exactly how close they are to the teenager) I believe you could tone down the scorn and try to reach a compromise. Fine, logic wins. Don't start rubbing it in their faces.