My father drove an '84 300D 463K miles before an oil ring blew. Original tranny and everything. Of course the car was driven on the highway most of it's life.

The 300SD, if you're not used to it, can be a huge boat to drive. I came from an '85 300D into that car. It seemed to be a lot heavier then the 300D, and handled heavier too. 225K miles on a well maintained diesel is like nothing at all. It's just broken in at those miles.