Years

The Mercedes-Benz 300D served as the diesel-powered variant of the brand's mid-size executive sedan lineup, first appearing in 1975 on the W115 chassis before continuing through the W123 and W124 generations. It was positioned as a fuel-efficient, durable alternative to gasoline models, targeting buyers who prioritized longevity and low running costs. The W123-generation 300D, produced from 1976 to 1985, became particularly well known for the longevity of its OM617 five-cylinder diesel engine. Typical strengths across its generations included robust build quality, strong fuel economy, and the ability to accumulate very high mileage with proper maintenance.

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  1977-1985

  The Mercedes-Benz 300D (W123) was sold from 1977 to 1985, initially with a naturally aspirated 3.0-liter five-cylinder diesel and, from 1981, a turbocharged variant producing roughly 120 horsepower. Common service items include glow plug and fuel filter replacement, injection pump and injector maintenance, and timing chain inspection on high-mileage engines. These cars are also prone to rust in the floor pans, fenders, and trunk, and aging vacuum and rubber components can affect turbocharged models.