What is a primary requirement for hydraulic fluids?

The primary requirement for hydraulic fluids is their ability to remain incompressible. This characteristic is crucial because hydraulic systems operate based on the principle of transmitting force through the fluid. When pressure is applied in a hydraulic system, the incompressibility of the fluid allows the force to be effectively transferred throughout the system, enabling components to function as intended without significant loss of power or performance.

While hydraulic fluids should indeed have stable viscosity under varying temperatures and should not retain moisture, the fundamental expectation is that they remain incompressible to ensure reliable operation. If the fluid were compressible, it would lead to inefficiencies and potential system failures since the pressure exerted would not translate directly to movement or force generation in the hydraulic components. This incompressibility is what distinguishes hydraulic fluids in their role within hydraulic machinery and systems.