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Old 09-08-2003, 12:26 PM
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sixto sixto is offline
smoke gets in your eyes
Join Date: Jun 2000
Location: SF Bay Area
Posts: 20,114
Difficult to tell over the course of a weekend or PPI but the M103 engine is known for oil consumption as it wears. Valve seal deisgn or materials were changed over the life of the M103 and a 91 should have the latest iteration. Still not a hermetic seal.

The 100-150K mile range is when oil consumption starts to pick up. MB considers up to a quart in 1000 miles to be normal. Even says so in the manual, I think. Mixed reviews on whether synthetic oil helps or hurts. Changing valve seals is a ~$400 job that doesn't require pulling the head and will curb consumption for 20-50K miles, maybe more. Not a bad DIY job but not fun as I define it (and replacing a tranny by myself is fun for me).

Trannies typically go 150-200K miles. Those that last longer are on borrowed time, IMO. Most often it's a slow death and it will be unpleasant to drive before it's impossible to drive.

And to save you a post, expect the engine to turn more than 3000rpm at 65mph. It's a 4-speed AT with second gear start and 1:1 fourth gear. First gear will let you climb a wall.

95 S420
91 300SE
87 300SDL
83 300SD
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