Which property of hydraulic fluid is critical for its ability to operate at various temperatures?

The property of hydraulic fluid that is critical for its ability to operate at various temperatures is viscosity. Viscosity refers to the thickness or resistance to flow of a fluid, and it significantly affects how well the hydraulic system can perform under different temperature conditions.

As temperature changes, the viscosity of hydraulic fluid can either increase or decrease. At high temperatures, fluids typically become less viscous, allowing them to flow more easily, which can be beneficial for reducing pump load and increasing system efficiency. Conversely, at low temperatures, fluids can become more viscous, leading to sluggish movement and potential issues with flow and pressure in the system. Therefore, the viscosity of the hydraulic fluid must be appropriate for the operating temperature range of the system to ensure optimal performance and reliability.

Other properties such as density, conductivity, and corrosiveness are important in their own right but do not primarily influence the fluid's performance across the varying temperature ranges as viscosity does.