(Note: this may or may not be a correct picture of the 1923 Benz diesel truck, as the only images available from Daimler’s site are of the 1924 Mercedes diesel truck. But it’s of a similar vintage).
Yesterday we featured the first American diesel truck, the 1933 Kenworth. By that time, Benz—and then Mercedes-Benz after their merger in 1926—had been building diesel trucks for a full decade. Given that Germany was home to Rudolf Diesel as well as high fuel prices, it’s not too surprising that they pioneered in bringing this more efficient and economical power plant to mobile applications, starting with tractors (1922) and trucks (1923).
Daimler’s Mercedes was one year behind, with this, their first diesel truck appearing in 1924, although some sources cite 1923. So strictly speaking, the sign in its bed celebrating “10 years in service” wasn’t quite technically correct, depending on which date is correct, but it’s close enough, and it was quite an achievement. The truck itself is a Mercedes 5 K3, with a five tonne rating.
The Benz engine was the OB2, a four cylinder that made all of 45 hp @1000 rpm. It used a precombustion chamber to start the combustion process, a feature that would be widespread and used by Mercedes trucks until 1964, when the more efficient direct injection system replaced it.
The 1924 Mercedes diesel used air-blast injection. This was a common system before high pressure injection pumps became more widespread. A simple low-pressure fuel-feed-pump supplied the injection nozzle with fuel. At injection, a blast of compressed air presses the fuel into the combustion chamber, hence the name air-blast injection. It was more primitive, and adjusting the speed was problematic, thus it was more suitable to stationary engines.
The diesel was at least 25% more efficient than a comparable gasoline engine; total fuel costs were up to 86% lower, since the diesel could run on cheap tar oil, gas oil, kerosene, Texas oil, or paraffin oil. It wasn’t picky; I’m sure it would have happily digested the more expensive vegetable oils too.
After their 1926 merger, the trucks (and cars) were all named Mercedes-Bnz, and the diesel truck line soon expanded to both lighter and heavier trucks, like this L10000 from 1936. Its 12.5 L inline six made 150 hp, with a fuel consumption of 42 L/100 km (5.6 mpg).