scope:

This International Standard describes two procedures for calculating the viscosity index (VI) of petroleum products and related materials, such as lubricating oils, from their kinematic viscosities at 40 °C and 100 °C.

Procedure A is applicable to petroleum products of viscosity index up to and including 100.

Procedure B is applicable to petroleum products of viscosity index 100 or greater.

NOTE The results obtained from the calculation of VI from kinematic viscosities determined at 40 °C and 100 °C are virtually the same as those obtained from the former VI system using kinematic viscosities determined at 37,78 °C and 98,89 °C.

This International Standard does not apply to petroleum products with kinematic viscosities less than 2,0 mm²/s at 100 °C. Table 1 applies to petroleum products with kinematic viscosities between 2 mm²/s and 70 mm²/s at 100 °C. Equations are provided for calculating the viscosity index of petroleum products having kinematic viscosities above 70 mm²/s at 100 °C.

NOTE In cases where kinematic viscosity data are not available at temperatures of 40 °C and 100 °C, an estimate may be made of the viscosity index by calculating the kinematic viscosity at temperatures of 40 °C and 100 °C from data obtained at other temperatures. Such viscosity index data may be considered as suitable for information only and not for specification purposes.