In this paper, a computational fluid dynamics (CFD) code is applied to two- and three-dimensional simulations of windage power loss (WPL) generated by spur gears rotating in air. Emphasis is placed on the various meshes associated with the Finite Volume Method (FVM) and on the choice of turbulence model. Comparing CFD predictions with the power losses measured on a specific test rig, it is shown that the fluid ejection in the radial direction must be included in order to reproduce the experimental evidence. The relative importance of the losses generated by the gear front and rear faces along with those due to the teeth is discussed. The volumetric flow rate expelled by the teeth is analysed and the influence of flanges is highlighted.