ISO Viscosity Grade (ISO VG)

The ISO VG (Viscosity Grade) classification is recommended for industrial applications. The reference temperature of 40 °C represents the operating temperature in machinery. 

This classification defines 20 viscosity grades in the range of 2 to 3200 square millimeters per second (1 mm2/s = equals 1 cSt) at 40ºC (104ºF). For petroleum-based liquids, this covers approximately the range from kerosene to cylinder oils.

Minimum and maximum values of each grade ranges ±10% from the mid-point. For example, ISO VG 100 refers to a viscosity grade of 100 cSt ± 10% at 40°C.