That makes sense that the '89 has the M103 which I believe the 300E had as well. As far as reliability is concerned, it sounds like this engine is fairly robust. I heard that oil leaks and valve guides can be a problem. The owner of the '89 CE says it drips a bit of oil on the garage. I guess I will take a look when I go see the car. It only has about 60k miles. Now what oil do you guys suggest for an older, low mileage car like this one? Will synthetic cause problems? I have an older air cooled Porsche and I have been using non-synthetic oil with a high level of zinc to condition the metals in the engine. Then again, the Porsche has flat tappets where the Mercedes has hydraulic lifters. As far as fuel, I understand premium is recommended. Is that just 91 octane or is a higher octane required?