MB853

Three cylinders of 115 × 140 mm made 4.36 liters and 60 PS at 2,000 rpm, and marked the point at which the 850 series ran out of room in a straight line. Everything larger used the identical cylinder in vee form: the four-cylinder MB 854 at 80 PS, the six-cylinder MB 856 at 120, and the 11.6-liter eight-cylinder MB 858 at 160 PS for 890 kg. Below sat the twin MB 852 and the single MB 851. Direct injection, water cooling and a 505 kg dry weight say plainly what sort of duty was expected.

Rated speed was the defining decision. At 2,000 rpm the pistons moved at 9.33 m/s, slow enough to be worked continuously without complaint, and the 18.5:1 compression ratio with direct injection made the engine frugal rather than lively. That is precisely what an industrial customer specified, and it explains why a half-tonne three-cylinder Mercedes-Benz made commercial sense in the 1960s in a way it never could in a vehicle. Daimler-Benz ran the water-cooled and air-cooled versions side by side to the point where one parts book covered both.