What type of fluid is commonly used in hydraulic systems?

Hydraulic oil or hydraulic fluid is the commonly used type of fluid in hydraulic systems due to its specific properties that enhance system performance and reliability. One of the key attributes of hydraulic oil is its ability to transmit force effectively while providing lubrication to the moving parts within the system. This lubrication reduces wear and tear, which is vital for the longevity of hydraulic components.

Additionally, hydraulic fluids are formulated to withstand a broad range of operating temperatures and pressures. They often possess anti-corrosive and anti-foaming properties, which help maintain efficiency and system integrity over time. Moreover, these fluids typically have a higher viscosity index, meaning their viscosity changes less with temperature variation, ensuring consistent performance under different operating conditions.

While options like water and vegetable oil can sometimes be used in specialized applications, they generally do not offer the comprehensive benefits that hydraulic oils provide, such as better protection against thermal degradation and moisture absorption. Compressed air, while essential in pneumatic systems, does not have the capability of transmitting power like hydraulic fluids do and therefore is not applicable in hydraulic systems.