Which property of hydraulic fluids is crucial for effective lubrication?

The property of hydraulic fluids that is crucial for effective lubrication is the viscosity index. The viscosity index reflects how the viscosity of a fluid changes with temperature. Fluids with a high viscosity index maintain a more consistent viscosity across temperature variations, which is essential for ensuring that adequate lubrication is provided under different operating conditions.

Effective lubrication reduces wear and tear on moving components, helps prevent metal-to-metal contact, and promotes the efficient operation of the hydraulic system. A stable viscosity under varying temperatures means that the fluid can provide sufficient lubrication even when the system experiences changes in heat due to operational demands or environmental conditions, thereby enhancing overall system reliability and longevity.

The other properties mentioned, while important in their own right, do not directly affect the lubrication performance of hydraulic fluids in the same critical way as the viscosity index does.