Rudolf Diesel filed the patent for his signature engine in 1893. However, its installation in a passenger car didn't occur until 1933, when Citroën installed a diesel engine into a Rosalie bay, although this car was never authorized to run on roads. Not until 1936, when Mercedes showed off the 260D, can we talk about the first successful diesel car on the road. Based on the 200 model, the 260 used a 2.4-liter I-4 engine named OM 138 mated to a Bosch mechanical injection pump. The ensemble allowed the car to produce 45hp of power at 3,200 rpm. Almost 2,000 units were built through 1940. The car initially has a 3-speed gearbox; and was upgraded with electric coil ignitors in 1938.
One of the diesel powerplant's main benefits – then as now – was reduced fuel consumption. The 260D burned 9 l/100 km (26 mpg U.S.) compared to 13 l/ 100 km (18 mpg U.S.) in the gasoline counterpart. Another bonus: at the time, diesel was half the price of gasoline, so the motorists saved a lot of cash at the pump.