Apparatus for testing shear stability of lubricants

Claim 1

A test method for predicting the shear breakdown of a polymeric high molecular weight Viscosity Index lubricating oil additive in lubricating use under conditions of high mechanical shear as in automotive crankcase oils and automatic automotive transmission fluids, which comprises forming an oil solution of said additive, measuring the viscosity of said solution, adding said solution to the test cell of a test instrument comprising a test cell, a roller bearing assembly within said test cell comprising a pair of races separated by roller bearings, one of said races being fixed within the test cell, and the other race being mounted on a shaft rotated by a motor, means for pressing said race mounted on said shaft against the race fixed in said cell to thereby exert a predetermined load on said bearings, rotating said races relative to each other at a constant speed and temperature for a given period of time to thereby obtain a rolling and shearing action on said oil solution of said polymeric additive, removing said solution from the instrument, and measuring the change in viscosity of said solution to thereby indicate the shear breakdown of said polymer.