The research aimed at finding an effect of various base oils on the scuffing initiation, scuffing propagation and pitting. The following base oils were tested: mineral oil, synthetic hydrocarbon oil (polyalphaolefins), synthetic non-hydrocarbon oils (polyol ester, polyglycol) and highly refined mineral one known as a white oil. The tests were performed in two different four-ball testers. One was used to investigate scuffing at pure sliding friction. The second instrument was employed to test pitting at rolling movement. To avoid an effect of the oil viscosity, base oils having similar viscosities ν100 (3,8 – 5,5 mm2 s−1) were compared. In this group the highest load causing the scuffing initiation is given by the polyglycol, and the lowest one — by polyalphaolefins and white oil. The scuffing propagation is similar for all the oils. The best resistance to pitting is given by the mineral oil, and the worst — by the white oil.
