A method of operating a hydraulic pump, comprising: a. filling a hydraulic system oil reservoir with a hydraulic oil comprising: i. a lubricant base oil having defined properties: and ii. an antiwear hydraulic oil additive package; wherein the hydraulic oil has an air release at 50.degree. C. less than 0.8 minutes; and b. operating the hydraulic pump without pump cavitation. A hydraulic system, comprising a hydraulic system oil reservoir holding a hydraulic oil comprising: i. a lubricant base oil, optionally having defined properties; and b. an antiwear hydraulic oil additive package; wherein the hydraulic oil has an air release at 50.degree. C. less than 0.8 minutes. In one embodiment the hydraulic oil additionally has low foam tendency and good demulsibility.