MB861

Air cooling was the odd choice here. Daimler-Benz built water-cooled engines almost without exception, and the 860 series was the deliberate departure: the same 115 × 140 mm cylinder as the water-cooled 850s, the same 2,000 rpm rated speed and the same 20 PS per cylinder, but finned barrels and a blower where the radiator had been. The MB 861 was the smallest of them — a single cylinder of 1.45 liters, 20 PS, and a fuel consumption of about 180 grams per horsepower-hour.

An engine that heavy for that little power only makes sense if it is expected to run for a very long time with nobody watching it, and that was the market exactly. Daimler-Benz had been in it since the 1920s with horizontal slow-runners sold to drive irrigation pumps and stationary installations, specifically in places where trained personnel were not available; air cooling removed one more thing that could freeze, boil or leak on a remote site. The larger members of the family did the same work at greater scale — the eight-cylinder version of 160 PS was offered in 1964 as a marine, generator, stationary and industrial engine.