There are many types of hydraulic oil. For example, large jet airliners use phosphate ester hydraulic oil; metallurgical and casting and forging hydraulic systems use water-glycol hydraulic oil; coal furnace hydraulic supports mostly use water-packed hydraulic oil. Oil or water-in-oil hydraulic oil. Different types of hydraulic oil have different main components. And most hydraulic oils are protected by patents, and their ingredients and formulas cannot be leaked at will. Hydraulic oil uses liquid pressure energy.