What is the significance of the viscosity index in hydraulic fluid analysis?

The viscosity index (VI) is a crucial measure of a hydraulic fluid's ability to maintain a stable viscosity across a range of temperatures. Viscosity refers to a fluid's resistance to flow; a high viscosity means the fluid is thick and flows slowly, while a low viscosity means it's thin and flows easily. A high viscosity index indicates that the fluid's viscosity changes relatively little with temperature fluctuations. This is highly desirable in h....