Relating High-Temperature, High-Shear Viscosity to Bearing Oil Film Thickness Measurements
SourceThe ASTM Bearing Oil Film Thickness Task Force was formed to establish a series of reference oils and to relate engine bearing film thickness measurements to oil rheological and compositional properties. Using seven Newtonian oils, a test method was developed. It consists of a capacitance technique run at several steady-state speed, torque, and temperature conditions. Evolution of equipment and techniques is presented. Normalized results from seven laboratories showed good agreement, precision, and correlation with oil viscosities. The task force's reason for being is a program to evaluate eighteen monograde and multigrade oils including four viscosity modifier types and all viscosity grades of significant interest. Analysis of available results is presented. Other recent published information on bearing film thickness measurements is summarized.