The most extensively referenced industrial oil classification is the one established by ANSI/AGMA (American National Standard Institute/American Gear Manufacturers Association) that classifies industrial gear oils where gear oils are classified into four types as shown in the following table :
AGMA Gear Oil Classification for Enclosed Gear Units for Industrial Applications
AGMA Gear Oil Classification for Semi-Enclosed Gear Units and Open Gears for Industrial Applications
In gear lubrication, the most important performance property is viscosity and, depending on the gear configuration, number of gear teeth, operating conditions, etc., Gear oil of appropriate viscosity needs to be selected. As for the viscosity classification of industrial gear oils, AGMA specifies it for high-viscosity grades, too.
AGMA also adopted a viscosity number specifying kinematic viscosity from 37.8℃ to 98.9℃ as in open gear applications. ANSI/AGMA classification is used in general for viscosity classification of industrial gear oils. The following table shows the mapping between ISO viscosity classification and ANSI/AGMA viscosity classification: