8bender, to the best of my knowledge "factory fill" for that vintage engine was 15W40 mineral oil. So IMO it's best to use Mobil 1 15W50 in that engine. That's the oil I have been running in our early-to-mid 1990's MB vehicles for the past 18 years. I change oil (and filter) every 7,500 miles.

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Fred Hoelzle