Scott, Mark, Barry, I appreciate the thoughtful advice. Mark we're in roughly the same boat sans severe mileage drop. I have noticed it dip a touch however.

This is the first diesel and the only w123 I've ever driven. Therefore, any improvements I experience are entirely relative. To be honest, I don't actually have any real issues (that I'm aware of). The car starts on the first crank, has a fine idle, mileage is in the 25-26 range. Hills are an issue though. I live on a very steep street and pulling out of my drive way in the morning to climb it is a bit of a joke. I'd estimate 7-8 mph and obviously in first gear the entire way. I also struggle mightily to keep over 50 on a highway grade, say 4%.

More than anything, I find incremental improvements to be very satisfying. I imagine we all do. Because I have no clue what this car was like off the assembly line, the idle can always be a little smoother, engine quieter, and hills more surmountable than they presently are.