This study presents a test campaign carried out at IFPEN aimed at understanding and characterizing the thermal behavior of electric motors incorporating direct oil cooling. Several cooling systems and oils are evaluated at different operating points, and the effect of parameter variations is investigated. Experimentations are defined and performed to understand and quantify the impact of different oils and direct cooling systems on the performances of the electrical machine. The test results make it possible to verify and quantify the gain on the thermal behavior obtained by adding an oil injection system directly to the active parts of the machine in addition to an indirect water jacket cooling. This gain is observed for a representative set of operating points and oil injection parameters. The impact of physicochemical properties of oils on direct cooling performance is assessed by a comparison of several oils. The viscous friction losses are also identified. The results presented include a repeatability and reproducibility study for speed values up to 14 krpm and continuous powers up to 60 kW.