I've heard of million mile MB's, but the highest mile car I've seen personally is a 1987 190D 2.5 with 1.1 Million kilometers (683,000 miles) that has not had the bottom end apart. There is a traveling doctor in southern Alberta with a 1984 190D 2.2 with 1.3 Million KM's on his car, but I haven't seen anything verifying it other than the fact that my Dad's known him since he bought the car back in 1984. (that's 807,000 miles) I don't know if the bottom end has been apart or not.
1 million miles in seven years? That's 142,857 per year or 391 per calender day. Suppose he does that 800 per "driving" day. That's 1250 driving days. That's 62 working months at 20 working days per month. If he did need to drive that 800 miles per working day, the mileage he attained is realistic.
I could see it lasting. Why? No cold starts or extended idling. The truck is 1995, so it's not sat around for a couple decades rotting (time is harder than miles, imho).
As to "synthetic" vs "not synthetic" I really couldn't care as long as the oil performs the way I want it to. I need SUPER LOW pour points (it was -34 here yesterday morning), and that cold weather protection is all I'm interested in.
The Mobil 1 I use (tri-synthetic) is liquid at extremely cold temperatures. It performs just like the 'ol Mobil 1 used to where I need it to.
As to the debate of extended change intervals, I don't care. I change the Mobil 1 at the same intervals that I used to do Dino. And the extra cost? I've been buying my Mobil 1 for about $4.00 a litre at Wal-Mart, which is only about $1 more than regular oil. That's only $7 an oil change difference.
1998 C230 "Black Betty"