Taking a look back: The first-ever diesel truck

In News, Mercedes-Benz5 MinutesBy NZ Trucking magazineJune 18, 2021

The world‘s first diesel truck was launched all the way back in 1923 by Benz & Cie. Test after test in challenging terrain, combined with public scepticism and some slow sales, the history of the diesel truck is an interesting one.

Work on the new truck engine began in 1922. And in the September of that year the first major assembly was put on the test stand, with the first test drive carried out in the Northern Black Forest in Gaggenau, Germany in September 1923.

The five-tonne vehicle was driven by a four-cylinder diesel OB 2 engine with an output of 33kW (45hp) at 1000rpm. When compared with a petrol engine, the diesel engine achieved fuel savings of 86%.

“The favourable consumption is particularly impressive: supplied with brown coal tar oil, the OB 2 requires around 25% less than a petrol engine with the same power,” the engineer’s report read at the time of the test drive.

Benz engineers chose the chassis on the Benz 5 K 3 truck, which was designed for a payload of five tonnes. During the test drives, the OB 2 diesel engine proved itself to such an extent that on 14 April 1923 it was decided that the engine would go into series production.

Rewind to 1911, Daimler-Motoren-Gesellschaft began development of a compact diesel engine for commercial and agricultural purposes. While Benz & Cie. were developing the diesel truck, DMG in Berlin-Marienfelde was building an air-injection diesel engine to be fitted in a truck that boasted almost the same power.

The finished product was a four-cylinder engine with an output of 29kW (40hp) at 1000rpm. The engine proved its road capability during a series of test drives in 1923.

The long-distance drive between the two DMG plants was particularly spectacular at the time: from 20 to 30 September 1923 a Daimler diesel truck drove from Berlin to Stuttgart and back. Following these tests. which drew a great deal of publicity due to the then enormous distances, the first Daimler 5C commercial diesel vehicles produced in Marienfelde – a truck, a three-sided tipper and a bus – were presented at the beginning of October 1923 at the Berlin automobile exhibition.

In 1926, Benz & Cie merged with DMG. Benz’s prechamber principle prevailed against the air-injection diesel engine. The first jointly developed prechamber diesel engine was the six-cylinder OM 5 engine from 1927 (55kW/75hp with a displacement of 8.6 litres). 

The Mercedes-Benz L 5 truck was fitted with either the new OM 5 diesel engine (51kW/70hp at 1300rpm) or a petrol engine, type M 36 (74 kW/100 hp at 2000 rpm). The five-tonner was the only model with a diesel engine to be included in the new Mercedes-Benz commercial vehicle range presented in 1927. Both the 1.5-tonne and 3.5-tonne vehicles were initially only available with petrol carburettor engines. 

The OM 5, which went into series production in 1928, was fitted with the new Bosch injection pump. Robert Bosch had begun working on the diesel injection pump in 1922. In 1927 the systematically improved injection technology was presented and contributed to the acceptance of the diesel drive. Bosch himself was convinced of the diesel engine’s superiority: in 1924 he was one of the first customers to order a diesel truck from Benz & Cie.

Initially, sales were slow because opponents of the new truck design criticised the loud and harsh running of the diesel engine. 

However, in June 1928 a 5-tonne diesel truck was delivered to British Mercedes-Benz Ltd. Commercial Motors, a specialist magazine of the time, praised the characteristics of the Mercedes-Benz truck in five consecutive issues. 

Then in the autumn of 1928, the Royal English Automobile Club awarded Daimler-Benz AG the Dewar Trophy, which was presented annually for special performances in the field of motor vehicle construction.