In this paper, a computational fluid dynamics (CFD) code is applied to a two and three dimensional study of windage power loss (WPL) from a single spur gear. Finite Volume Method (FVM) meshing and turbulence modelling choices are discussed. By comparing CFD findings to measured power losses on a specific test rig, it appears that only a model which reproduces a fluid ejection in radial direction can give accurate results. The relative importance of losses which occur at faces and those at teeth is discussed.