Full definition
Working fluid in hydraulic systems. Functions: transmit force (incompressibility), lubrication, corrosion protection, heat dissipation. Classification ISO 6743-4: HH (no additives), HL (antioxidant/anticorrosive), HLP (also anti-wear — most common), HVLP (high VI for temperature swings). Viscosities: ISO VG 32 (hot climate), VG 46 (standard), VG 68 (high temperature). Biodegradable: HETG (triglycerides), HEES (synthetic esters). Brands: Shell Tellus, Mobil DTE, Petro-Canada Environ.