The development of a standard ASTM test method for measuring engine oil viscosity at high temperature (150°C) and high rate of shear (10⁶ S^-1) is discussed. A review is provided of the ASTM interlaboratory program that incorporated several different viscometer designs to evaluate a single generalized procedure for viscosity determination. A statistical analysis for ASTM repeatability and reproducibility resulted in a level of precision that approached that of rotational high-temperature, high-shear viscometers. Excellent correlation between capillary viscometers and rotational instruments is also demonstrated. The method is applicable to existing high-temperature, high-shear viscosity requirements in the European Committee of Common Market Automobile Constructors (CCMC) specification as well as individual high-temperature, high-shear specifications established by original equipment manufacturers.