OM402

Because the 400 series held to a 90° bank angle across six, eight, ten and twelve cylinders, and because each crankpin served a pair of opposed cylinders, even firing intervals fell out of the geometry for the V8 alone. That made the 12.8-liter OM 402 the natural center of the range at 256 PS and 834 N·m from 1,400 rpm. The whole family was developed with MAN, the two firms sharing all but a handful of parts and differing chiefly in how they burnt the fuel — MAN with the bowl of its M-process, Daimler-Benz with plain direct injection.

In the New Generation trucks it appeared as the 1624 and 1626 at 240 and 256 PS, and in the heavier 2224, 2226 and 2626; the O 303 coach of 1974 offered it as the middle of three. Like the V6 it outlived its own replacement, because no naturally aspirated engine could be made clean enough for Euro I: back it came, turbocharged and intercooled, as the 381 PS OM 402 LA. By then the same block was selling as industrial plant through MTU, which took over distribution of Mercedes-Benz truck engines outside the firm's own vehicles in 1988.