One thing to check is to make sure your odometer is measuring the miles correctly. The 123's are notorious for slipping gears in the odometer, which gives you a false milage reading. You can it check versus mile markers along the highway.

Good luck!

__________________
1976 240D
1987 560SL
2007 E320 Bluetec
1998 C280 (now son’s car)
1982 240D Manual - Sold