When most people think of diesel engines, they often picture heavy-duty trucks and locomotives — or they might recall Volkswagen’s Dieselgate scandal – but diesel power actually made its passenger car debut nearly a century ago. While the 1936 Mercedes-Benz 260 D is often credited as the first production car with a diesel engine, the full story goes back a bit farther and includes earlier prototypes — plus a surprise appearance from a French automaker.
The diesel engine takes its moniker from its inventor, Rudolf Diesel, who patented his first-of-its-kind compression ignition engine in the 1890s. Unlike gasoline engines, which use spark plugs to ignite air and fuel within the combustion chamber, diesel engines rely on compressing air to intense pressures and temperatures before injecting fuel. The resulting combustion is not only powerful, but highly efficient. These qualities made it ideal for both industrial and commercial use.
Early applications of diesel power were seen in ships, trains, and factories because these massive engines were far too heavy for the compact personal vehicles of the time. It wasn’t until the early 20th century that automakers began to seriously experiment with smaller, more roadworthy versions.
Enter the Benz
Mercedes-Benz unveiled the 260 D – internally designated the W 138 – at the Berlin Motor Show in the spring of 1936. It was a pullman landaulet model that could comfortably seat six that was powered by a 2.6-liter four-cylinder diesel engine and boasting a modest 45 horsepower. It wasn’t showy or particularly powerful, but it was efficient, reliable, and consumed less fuel than its gas-powered counterparts.
Mercedes put it into full production in September of that year, selling nearly 2,000 units between its introduction and December 1940. They introduced three sedan versions in addition to the flagship pullman, which became particularly popular with taxi operators who were highly appreciative of its fuel efficiency. The 260 D’s significance isn’t that it was the very first diesel powered vehicle, but rather that it was the first diesel-powered passenger car produced at scale and marketed to everyday drivers. Its OM138 engine set a standard for durability and fuel economy that would become the hallmark of diesel engines for years.
Still, just because Mercedes-Benz made it to production and sale to the general public first does not mean that French automaker Citroën doesn’t deserve its fair share of the credit for the diesel engine’s launch. Three years before the debut of the 260 D, Citroën fitted one of their 7U Rosalie models with a diesel engine, and built a handful of successful prototypes based on the 7U platform. While these cars weren’t available to the public or produced in quantity, they were drivable and road-tested.
Diesel’s legacy and future
So while most historians acknowledge that Mercedes-Benz deserves credit for being the first to truly produce a diesel passenger car at scale, Citroën rightly deserves recognition for showing that diesel wasn’t just an idea for tractors, trucks, and tankers. It provided a glimpse of the future where diesel engines could be refined, road-worthy, and at home in a consumer vehicle.
Though diesel passenger cars never really took off in the U.S. market, they became staples across Europe, particularly in the decades post WWII. Mercedes-Benz’ 260 D and its subsequent iterations laid the groundwork for future diesel cars produced by other European automakers like Fiat and Volkswagen. In 1978, Mercedes-Benz was first again with its introduction of the turbodiesel 300 CD and 300SD with turbocharged engines delivering even more refinement and performance.
Today, diesel engines remain ubiquitous in commercial applications — trucking, agricultural vehicles, and shipping. However, these engines have faced scrutiny in recent years in the face of tighter and tighter emissions regulations and the rise of EVs. We don’t yet know exactly what the future holds for restrictions on diesel engines, as mandates are largely affected by the shifting political tides, but its clear that they’re here to stay in some form or fashion.
The 1936 Mercedes-Benz 260 D wasn’t fast — and certainly couldn’t haul heavy loads — but it did prove that diesel could work in a passenger car, paving the way for a new era of automotive engineering. For that, it earns its place in the diesel hall of fame, sharing the spotlight with the Citroën that quietly held the door open for its arrival.
