25,000 Mile Long-Term Test: 1977 Mercedes 300D – The Quirky Appeal Of Doktor Diesel


(first posted 11/ 15/2016)     Diesels were bursting (or smoking and rattling) onto the American automotive scene with full force by the late 1970s, offering strong fuel economy benefits as an antidote to the trade-offs required by lethargic performance and searching for fuel at truck stops.  An undisputed leader in the Diesel Movement in the U.S. was Mercedes-Benz.  For 1977, Mercedes introduced the new W123 platform to the U.S. and naturally a core offering was the recently introduced 5-cylinder Diesel.  Car and Driver ran a long-term road test on the W123 300D, seeking to understand the good and bad over time—their conclusions were reported in the May 1978 issue.




The harsh reality of Diesel operation was that the cost/benefit equation wasn’t particularly strong.  For long-term, high-mileage use, yes, the Diesel would ultimately pay off economically.  However, for many luxury Diesel customers, the real appeal was in showing off a “fuel efficient” mindset—very much in vogue after the first OPEC crisis.  The Diesel, oddly enough, became a style statement for wealthy suburbanites.  Things are no different today: Tesla owners bask in ecological smugness and green superiority as they charge their electric chariots at their energy-sucking monster houses.


CAFE (Corporate Average Fuel Economy) standards were also a major culprit in the rise of Diesels.  Manufacturers knew that American customers valued size and space, and those attributes would be incompatible with the high mileage figures being required by the Feds.  Diesels offered a solution, allowing cars to remain relatively large while still achieving the stricter mileage requirements.  GM leapt into the oil-burner fray for 1978 with the introduction of the Oldsmobile 350 V8 Diesel, which soon proved to be a quality and reliability disaster that badly tarnished the reputation of Diesel power in the U.S.


Mercedes-Benz, by contrast, showcased its mastery of the Diesel with the 300D, which offered a performance bump compared to the glacially-slow 240D.  The engine reinforced the pragmatic virtues of the Mercedes brand, and the overall excellence of the W123 platform was world-class for the time.  Owners who embraced Diesel for their Benz enjoyed the many virtues of the car, even as the suffered through the shortcomings of daily life with a smoker.  In fact, the allure was such that at the end of the test, Car and Driver’s own Leon Mandel bought the 25,000-mile test car and made it his own.


Clearly, the all-around excellence of the 300D made it irresistible, even with all the trade-offs involved over the long haul.  Given that the test-car in question was painted in a color resembling “Cream-of-Flamingo” soup, that must have been true love indeed.