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Current specifications for automatic-transmission fluids and gear oils have viscosity limits which are determined by ASTM D 2983. However, that test is plagued by poor precision. This paper describes the development of a method using the Mini-Rotary Viscometer to make the determination of apparent viscosity at the same nominal shear stress as ASTM D 2983. In this test procedure, samples are cooled in a manner similar to that described in ASTM D 2983. Experimental data were obtained on a mixture of 17 automatic-transmission and gear-oil fluids that included a number of different formulation strategies and commercial products. The results of this method yield a nearly one to one correlation with the results determined by ASTM D 2983.

A commercial High-Temperature High-Shear Capillary Viscometer (HTHS) has been designed and developed to meet the needs of the anticipated HTHS specification which may be included in the SAE Viscosity Classification J300 for engine oils. It is intended specifically for measuring the viscosity of engine oils a) at 150 +/- 0.1°C, 106 s-1 shear rate b) at high production rates c) with minimum operator attention and ease of calibration. The viscometer can be used for other tempertures and shear rates and for liquids other than engine oils.