Hydraulic fluids, also called hydraulic liquids, are the medium by which power is transferred in hydraulic machinery. Common hydraulic fluids are based on mineral oil or water, with biodegradable vegetable oil fluids (primarily based on canola oil) also becoming commercially accepted. Unmodified vegetable oil tend to oxidize easily; it may be advisable to protect the fluid from air exposure in equipment, use additives, or possibly continuously degas (e.g. ).
Examples of equipment that might use hydraulic fluids include excavators and backhoes, brakes, power steering systems, transmissions, garbage trucks, aircraft flight control systems, lifts, and industrial machinery.
It forms the basis for much of the power transmission for GVCS technologies.
Hydraulic systems like the ones mentioned above will work most efficiently if the hydraulic fluid used has low compressibility. Lubricating properties of the fluid are also important (particularly an issue with water-based fluids).
- Canola (rapeseed) field crop