Oil Film Thickness in a Bearing of a Fired Engine Part III: The Effects of Lubricant Rheology

This is the third interim report describing oil film thickness measurements in a bearing of a fired single cylinder engine.

The minimum oil film thickness (MOFT) in the front main crankshaft bearing of a fired CLR (Cooperative Lubricants Research) engine has been measured using a capacitance technique.

The effects of base stock viscosity, VI improver type and concentration, and finished oil viscosity at both high and low shear rates are presented and discussed. Five VI improvers are compared, and are found to have varying degrees of effectiveness in increasing MOFT in a given formulation and base stock. The shear rate and temperature of the viscosity measurement are found to affect the overall correlation between MOFT and oil viscosity.