However, after the introduction of the OM621, the OM636 was kept in production for industrial vehicles such as small lorries, boats, and combine harvesters, until 1990.

For a short period of time between January 1952 and August 1953, a facelifted version of the W136 (now having the chassis code W191) was sold.

In 1953, the W120 succeeded the W191, starting in 1954 it was offered with an upgraded version of the OM636, now displacing 1.8 litres and again making 40 PS (29 kW).

[2] The OM636 is a water-cooled inline-four-cylinder diesel engine with precombustion chamber injection, eight valves, OHV valvetrain and wet sump lubrication.

The camshaft is driven by gears, it also drives the inline injection pump.