Never change your oil, even synthetic, at 7500 miles in a 30+ year old diesel. Use quality dyno/synethetic 15w40 and change every 3k miles. When the car was brand new in 1980's, and the engine was new, it was okay to follow this recommended service interval 5000miles+. These engines are decades old and have hundred's of thousands of miles on them.

Doing an oil change is the most inexpensive maintenance item you can do, do it early, use quality parts, and have peace of mind.

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1976 Mercedes 240D (Sold)
1985 Mercedes 300D Turbo Diesel: 500,000KM
1986 Mercedes 300E (Sold)
1988 Mercedes 300E (Sold)
2002 Mercedes C240 (Sold)
2008 Mercedes C350 4matic

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Industrial Rubber