Not all hydraulic systems can utilise standard hydraulic oil as their operating fluids. Some require fire resistance, low viscosity index, high temperature boiling point, low viscosity. Using these fluids solves one problem and causes several others. MAN have recently designed and manufactured HPUs for use with Water, Water glycol (including sub-sea), DOT 5.1 brake fluid (glycol), turbine oils, silicone oils, phosphate ester and other ester based fluids.