Lubrication networks in today's passenger car engines are complex systems managing the interactions between the manufacturers' demand for long engine-life, low friction characteristics and sufficient heat-transfer work of the lubricant. Modern engines work harder and run hotter and consequently place more demands on the engine oil and the design of the lubrication system. The paper presents an overview of the influences of various oil pump parameters as oil pump suction port, rotor geometry and oil pump component clearances on the engine's operating behavior. The results of detailed investigations, intended to design the oil pump capacity exactly to the requirements of the optimized lubrication system, are shown in combination with the analysis of the oil draining system, aimed to reduce the hydraulic losses. A potential is presented that engine manufacturer can obtain in terms of saving energy.The positive influence on fuel consumption by a consequent improvement of the oil pump design, the reduction of the hydraulic losses within the lube system and the elimination of power train losses by minimizing the amount of splashed oil in the crankcase is demonstrated.