I resently purchased a 1993 300SD with 91k miles. It's burning a quart of 20/50 every 100 miles. My local Mercedes Whiz says valvue guides and/or valvue stem seals. I'm looking at an $1,800 repair bill. two questions: Is this a reasonable price and does anyone have any idea why this needs to be done with only 91K on the engine?

 

Check and be sure the rods are straight before putting money into the car.

A sign of bent rods is heavy oil consumption in 3.5 motors.

Not sure on 603s w/ self adjusting tappets but valve seals in general are not that hard to replace.