mbzman, it's possible that the timing chain tensioner needs to be replaced. Our 1992 300CE (with the 104 engine) had a valve train noise that concerned me. An experienced tech at our local MB dealer traced the noise to the tensioner. A new tensioner resolved the issue.

Factory fill for that vintage engine was 15W40 mineral oil. I run Mobil 1 15W50 in our 124 cars year round without any issues.

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Fred Hoelzle