Hydraulic oil

A hydraulic fluid or hydraulic liquid is the medium by which power is transferred in hydraulic machinery. Common hydraulic fluids are based on mineral oil or water.[1] Examples of equipment that might use hydraulic fluids are excavators and backhoes, hydraulic brake,power steering systems, transmissions, garbage trucks,aircraft flight control systems, lifts, and industrial machinery.

Function Property
Medium for power transfer and control
  • Non compressible (high  bulk modulus)
  • Fast air release
  • Low foaming tendency
  • Low volatility
Medium for heat transfer
  • Good thermal capacity and conductivity
Sealing Medium
  • Adequate  viscosity and  viscosity index
  • Shear stability
  • Viscosity for film maintenance
  • Low temperature fluidity
  • Thermal and oxidative stability
  • Hydrolytic stability / water tolerance
  • Cleanliness and filterability
  • Demulsibility
  • Antiwear characteristics
  • Corrosion control
Pump efficiency
  • Proper viscosity to minimize internal leakage
  • High viscosity index

Special function

  • Fire resistance
  • Friction modifications
  • Radiation resistance

Environmental impact

  • Low toxicity when new or decomposed
  • Biodegradability

Functioning life

  • Material compatibility