OM138

The experiment began in autumn 1933, when Daimler-Benz put 80 PS 3.8-liter diesel sixes into Typ Mannheim test cars and found the engine shook the chassis beyond any hope of production. The answer was a four using the same cylinder dimensions but deliberately lower specific output, ready in mid-1935. Its one-piece head carried pre-chambers set at roughly 45° and led out eccentrically, with injectors and glow plugs reachable from outside and the pushrods threaded through the head on the pre-chamber side — awkward to draw, easy to service in a yard.

It appeared at the Berlin motor show in February 1936, in the long Typ 200 chassis, as the 260 D. Hanomag exhibited a diesel Rekord in the same halls but did not start regular series production until 1938, which left the 260 D as the world's first series-built diesel passenger car. Almost every early one went into taxi work, where a 90 km/h top speed mattered far less than the fuel bill and the six-seat body. Some 5,719 engines were built to 1940 — well beyond the 1,967 cars, because the L 1100 and L 1500 light lorries and the O 1500 bus took it too.