Hydraulic oil with excellent defoaming and low foaming

摘要

This invention provides a hydraulic oil comprising: 1) a lubricant base oil having an average molecular weight greater than 475, a viscosity index greater than 140, and a weight percent olefins less than 10; and 2) an antiwear hydraulic oil additive package. The hydraulic oil of this invention has an air release by ASTM D 3427-03 of less than 0.8 minutes at 50 degrees C., and a sequence II foam tendency by ASTM D 892-03 of less than 50 ml. We describe a process for making the hydraulic oil of this invention, and a method of operating a hydraulic pump without pump cavitation using the hydraulic oil of this invention.