In 1935 a new heavy-duty truck with a payload capacity of 6.5 tonnes was launched, named the L 6500. There were two diesel engines available; the 10.3 litre OM 79 six-cylinder which developed 120 horsepower as well as the 12.5 litre six-cylinder OM 54 engine which produced 150 hp at 1700 rpm. A petrol M 78 engine which produced the same power rating as the OM 79 was an option, although very few examples with this engine existed and little information on this engine is known.
An LK 6500 tipper variant with a decreased wheelbase from 5,100mm to 4,350mm was produced as well as an LD 6500 turntable ladder version for use as a fire engine. In 1938 after feedback from customers Mercedes upped the OM 79's horsepower to 150 and the displacement to 11.2 litres. All models were fitted with a ZF 8-gear manual transmission.
2,137 examples were produced during the five-year production span of 1935-1940. The L 6500 was the predecessor to the popular L 6600 / L 315 range of the 1950s, and there were some similarities in the design of both models.