ISO (International Standards Organisation) viscosity classification
The ISO viscosity classification uses mm2/s (cSt) units and relates to viscosity at 40oC. It consists of a series of 18 viscosity brackets between 1.98 mm2/s and 1650 mm2/s, each of which is defined by a number. The numbers indicate to the nearest whole number, the mid points of their corresponding brackets. For example, ISO viscosity grade 32 relates to the viscosity bracket 28.8 to
35.2 mm2/s, the mid point of which is 32.0 mm2/s. This is illustrated in the table below, which shows the ISO viscosity grade numbers, the mid-points of each bracket, and the viscosity limits. This system is now used to classify all industrial lubricating oils where viscosity is an important criterion in the selection of the oil. Cutting oil and some other specialized products are more important in relation to grade selection.
ISO VISCOSITY GRADE (ISO VG)
|KINEMATIC VISCOSITY AT 40oC (mm2/s)|