With the turn of the century, the taxi changed from being something similar to the coach, into something more like the car of today, with the engine up front. Indeed, as shown in the above picture of the 1914 Benz 8/20, it was only later completely closed in. Former coachmen had to be schooled as taxi-drivers. The days of the coachmen's short naps were over.

At the beginninig of the First World War, the so-called Marne-Taxis became famous. They were recruited at short notice, to transport the 6,000 men of the 7th division, 5 men to a vehicle, via Paris to the front line on the river Ourcq. This considerably foiled the plans of the attacking Germans and forced the, until then successful, Marne-offensive into retreating because of the counter offensive.

There is indeed, another striking point in the history of the motor-taxi: the first Diesel engines for motor cars. This way Mercedes was able to secure the taxi market for decades. The Mercedes Diesel engines were even installed in a number of car bodies from other manufacturers, although not the first examples from 1936. They had the well known low fuel consumption and, perhaps even more important, the attribute of a favourable wear and tear behaviour, which was important for the necessary cold starting of the taxis in winter, the engine was however, weak, heavy, rough and ready and only available for the taxi enterprise.

Although the Bosch injection-pump for truck-engines had already been available since 1927, the attempt to transfer this combustion method to the smaller motor car engine appeared simply not to be a success. The high compression necessary for the spontaneous combustion, required a heavy-weight cylinder block and crank mechanism, which e.g., as a 3,8 liter six-cylinder was too much for the chassis. The engineers were in despair.

A completely new approach brough the necessary help. After Bosch altered their pump and from the 3,8 liter six-cylinder, a 2,6 liter four-cylinder with overhead valves and precombustion chambers was created, the engine was at least driveable, although the above mentioned unwanted features were still present.