An apparatus produces a diesel-oil/water microemulsion and injects the emulsion into a diesel engine. The apparatus has three high pressure cylinders, inlets of two of the high pressure cylinders are connected to a static raw emulsion premixer. Outlets of the two high pressure cylinders are connected to a homogenizing valve. An inlet of the third high pressure cylinder is connected to the outlet of the homogenizing valve and the outlet of the third high pressure cylinder is connected to the diesel engine. The three pistons of the three high pressure cylinders are constituent parts of a pressure booster whose drive piston is guided in a drive cylinder which is connected to a hydraulic drive unit.