![]() Standard ASTM D2270 Calculates Viscosity Index by Measuring the Kinetic Viscosity of Liquids at 40° and 100☌ and ASTM D567 Method for Calculating Viscosity Index from Viscosity at 100✯ and 210✯. In turn, this means consistent, high performance in the machine. The best oils with the highest VI are stable and do not vary greatly in viscosity over a wide temperature range. ![]() Viscosity Index was measured by a scale of 0 to 100 however, modern science of lubrication has led to the development of oils with very high VI. High-VI liquids, in contrast, are less affected by temperature changes. ![]() Thus, a fluid with a low viscosity index will experience a relatively large swing in viscosity as temperature changes. The higher the VI, the smaller the change in fluid viscosity for a given change in temperature and vice versa. ![]() We can say that the it is the dimensionless number that shows how the temperature change can affect viscosity of an oil (engine oil and automatic gear oils, and power-steering fluids). The viscosity index (VI) is an arbitrary, unitless measure of a fluid’s viscosity change relative to a temperature change. ![]()
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