ABSTRACT
Efforts to modify the high-temperature viscosity specifications have dealt primarily with developing correlations between oil film thickness measured in the journal bearings of operating engines and viscosities values measured at different high-temperature, high-shear rate conditions in laboratory viscometers. At the same time that engine oil viscosity has reemerged as an important issue with regard to engine design and performance, the deficiencies in the present method for specifying the high-temperature viscometric properties of engine oils have become more apparent. Most references have accomplished this task by simply draping a braided metal wire, one end of which is connected to ground, over the portion of the shaft extending outside of the engine. Depending on whether measurements of electrical resistance or capacitance are to be used in calculating film thickness values, different methods for applying a voltage across the bearing are employed.
