The internal friction of one oil molecule sliding over another is called viscosity. Viscosity is dependent on molecular size and shape and is used in various applications. It is important to know what viscosity grade is required for each piece of machinery you own. Below is a viscosity chart to help you determine what grade is right for you.

The International Organization of Standards created viscosity standards so that one standard would apply to for all viscosities of any fluid in the world. Below is a chart that shows the different grades of oil differing only by their viscosity and how they are categorized into specific ISO numbers. This chart is yet another tool to help you decide what oil is right for you.

Viscosity 1 (Consistency Grades for Lubricating Greases)

Viscosity 2 (SAE Viscosity Classification for Axle and Manual Transmission Lubricants)

Viscosity 3 (International Organization for Standardization (ISO) Viscosity Classification System for Industrial Fluid Lubricants)