Viscosity Index

The viscosity index (VI) measures how much a fluid's viscosity changes with temperature. Viscosity refers to a fluid's thickness or resistance to flow; for example, honey is more viscous than water. A high viscosity index means the fluid maintains its thickness better across a range of temperatures, making it more stable for use in engines and machinery. Conversely, a low viscosity index indicates that the fluid's viscosity changes significantly with temperature, which can affect performance. Essentially, a higher VI is preferred for lubricants, as it ensures consistent operation in varying temperatures.