In recent years, in order to optimize performance and exhaust emissions of internal combustion engines, the design of auxiliary systems assumed a particular importance especially due to the need to obtain higher efficiency and reduce power losses required by these components. In this sense, looking at the lubrication circuit, it appears important to use solutions that allow to optimize the fluid dynamics of both the ducts and the pump.In this paper a tridimensional CFD analysis of a lubrication circuit oil pump of a modern high-performance engine will be shown. In this particular application there is a variable displacement pump used to optimize the operative conditions of the lubricant circuit in all engine running conditions. This variable displacement pump changes the positions of the ring as a function of the boundary conditions.The model was build up with PumpLinx®, a commercial CFD 3D code developed by Simerics Inc.®, taking into account all the thermo-fluid dynamic conditions with particular attention to the cavitation phenomena. The model was also validated by data of an experimental campaign performed on a hydraulic test bench. The focus of this paper is to analyze phenomena which occur during the pump operation, as cavitation, to calculate the flow-rate limit during the eccentricity variations and, consequently, the displacement variation.Moreover the model allows to determine the forces between the pump rotating elements which influence the equilibrium of the ring and consequently the displacement variation.