The OM 668 makes use of the common rail system.

Compared to the otto engine M 166 it has 4 valves per cylinder instead of two.

In 1997 the OM 668 was the smallest diesel engine by Mercedes-Benz.

This increased the rated power, but not the torque, due to the weak clutch of the Mercedes-Benz W 168.

The OM668 later developed into the Thielert Centurion 1.7 aero engine *OM = Oelmotor (diesel engine),668 = engine series, DE = Direkteinspritzung (common rail injection), 17 = approximate Displacement in dl,A = Abgasturbolader (turbocharger),L = Ladeluftkühler (intercooler),red.