The current Mercedes S-class will receive an eco boost with the arrival of a four-cylinder diesel version next year.
Called the 300 CDI, the new model is expected to be powered by the E250 CDI’s 201bhp turbodiesel, pushing out 384lb ft of torque.
Mercedes' R&D boss Thomas Weber admitted that downsizing the S-class diesel was an engineering challenge.
"The issue is NVH [noise, vibration and harshness]," he said. "Getting refinement to S-class levels was difficult and we had to change engine mounts and add body stiffness".