Comparative overview of five gear oils in mixed and boundary film lubrication

► Mineral, ester and PAO oils were submitted to Stribeck type tests. ► Stribeck curves were drawn with a new x-parameter that improves oil comparison. ► The response of the oils to various operating conditions are analyzed. ► The base oil is most important in full film lubrication. ► Additives become determinant in mixed and boundary film lubrication.