The International Standards Organization created the ISO VG in response to the need for a globally recognized viscosity designation. It worked with other major engineering groups in the development of such a system. The ISO VG was born out of such an effort. As a result, engineers, practitioners and suppliers are now able to select and use liquid lubricants with minimal difficulty.
The ISO VG is essentially a classifying system and creates a viscosity measurement method so that all parties have a standardized basis for using industrial lubricants. Primarily, lubricants are classified on the basis of their kinematic viscosity at 40 degrees C. The kinematic viscosity relates a lubricant's resistance to force. The ISO VG system also establishes approximately 20 different gradients that range from 2 to 3,200 square mm per second. The key point is that there is a difference of at least 50 percent between subsequent grades.
An ISO VG simply allows a user to choose a lubricant that has the required viscosity for a machine's functioning temperature range. The actual VG value signifies a lubricant's average viscosity at 40 degrees C. For example, a lubricant with a VG value of 200 will have an average viscosity of 200 cSt (centistokes) at 40 degrees C.