Use of a Couette High-Shear-Rate Viscometer for Measuring the Viscosity of Engine Lubricants

A Couette viscometer is described which is capable of measuring the viscosity of engine lubricants at a temperature of 150°C and shear rates from 10⁵ to 10⁶ s^-1. A novel feature of the instrument is the introduction of an electrical capacitance method for measuring the size of the annular gap. Operating procedures are discussed in detail and mathematical corrections are established for dealing with temperature rise in the test sample. Viscometric data for some single-grade oils and multigrade oils are presented.