Viscosity index

The viscosity index (VI) is a measure of how much a lubricant's viscosity changes with temperature. It provides insight into the performance of lubricants under varying thermal conditions. A higher viscosity index indicates that a lubricant has relatively stable viscosity across a wide range of temperatures, meaning its performance is less affected by changes in temperature. Conversely, a lower viscosity index means that the viscosity of the lubricant is more susceptible to variations in temperature.