Years ago I drove a 300 series turbo diesel, it was truly a great car....think I got about 300,000 miles out of it until an employee of mine wrecked it....oh, and because the car was like a tank, they walked away from the accident unscathed.
I just got mine. It's an '85 (last year of the W123 chassis), and has only 172,000 miles. I'm hoping to get a fair number of miles out of it, but you never know.