OM57

In 1938 Daimler-Benz revised its two heaviest ranges together. The L 6500 and the N 56 chassis received reworked spur-gear hub drives and modern all-steel cabs, and both changed engines: out went the OM 54, in came the OM 57, still rated at 150 hp. It was another water-cooled prechamber six with overhead valves, a seven-bearing crankshaft, a low camshaft driven by spur gears off the crank and a Bosch pump injecting into the prechambers — but a tighter engine than the one it replaced, at roughly 11.2 liters against 12.5.

What followed was not much of a commercial career. Vehicles built for the Wehrmacht carried the standard-issue military cab and a de-rated version of the engine. N 56 truck production ended in 1939, L 6500 production at Gaggenau in 1940, and the bus chassis in 1941; the OM 57 went with them. When Daimler-Benz restarted lorry production after the war it began somewhere else entirely, with the small, high-revving OM 312 of 1949, and the heavy pre-war sixes were never revived.