I don't think the car will self-destruct at all....we've seen/heard examples over and over of people who leave dino oil in a car, with just top-ups, and have the car run 30 - 40,000 miles with little apparant damage. And we know that with regular top-us, Amsoil 0W30 'should go 35,000 miles, as per their claims, and still be in reasonable condition. So if he 'pushes it' and doesn't change it, it should still go probably twice that before it develops real problems, maybe even more. Remember, their is a synthetic that says you never have to change it...