The viscosity index (VI) is an arbitrary, unitless measure of the change of viscosity with temperature, mostly used to characterize the viscosity-temperature behavior of lubricating oils.
![Viscosity Table Viscosity Table](https://www.leahywolf.com/wp-content/uploads/2018/03/Viscosity-Table.jpg)
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Viscosity index Classification Under 35 Low 35 to 80 Medium 80 to 110 High Above 110 Very high