Viscosity index意思

Viscosity index (VI) is a numerical index that expresses the effect of temperature on the viscosity of a fluid. It is used primarily for oils and other petroleum products, and it is an indicator of the fluid's resistance to change in its viscosity with temperature.

The viscosity index is determined by measuring the fluid's viscosity at two different temperatures, usually 40°C (104°F) and 100°C (212°F), and then using a formula to calculate the index. A higher viscosity index indicates that the fluid has a lower change in viscosity with temperature, which means it will maintain its viscosity over a wider range of temperatures.

Viscosity index is important in the selection of oils and lubricants for use in engines and other machinery, as it helps to ensure that the oil will provide adequate lubrication over a range of operating temperatures. Oils with a high viscosity index are generally more desirable, as they are less likely to become too thick or too thin at extreme temperatures.