The L 5 model was presented in 1927 at the Cologne international commercial vehicle show with the newly-designed OM 5 diesel engine which utilised Bosch's diesel fuel injection technology. The vehicle produced 70 horsepower at 1,300 rpm from an 8.6 litre straight six-cylinder engine. It was the first mass-produced diesel powered truck, and the OM 5 was the first six-cylinder diesel engine intended for use in vehicles.

The L 5 had a payload capacity of 5 tonnes as the name indicated. The “L” stood for lastwagen, which is German for truck.

Also available was a low-chassis version named the N 5 which was primarily used for buses, and for those who preferred traditional petrol power, a 100 horsepower M 36 petrol engine was available.

The new diesel truck received criticism at first as it was rough and noisy, unlike the smooth petrol engine it was attempting to replace. In 1929, to promote the new technology that was largely unknown around Germany, a Mercedes L 5 toured around the country advertising the diesel engine's advantages over petrol power.

1927 Mercedes L 5 flatbed
An L 5 model was delivered to England a year earlier in 1928, where it was extensively tested by the Commercial Motor magazine. The results were so impressive that the Royal Automobile Club (RAC) awarded Mercedes with the prestigious Dewar Trophy, an award given to vehicle manufacturers in recognition of remarkable achievement in automotive design.

In 1930 Mercedes' model designation system was changed. The new layout was a letter describing the vehicle type, then four digits standing for the payload in kilogrammes. This meant the L 5 became the L 5000.