(57) A methylpolysiloxane oil containing CH₃SiO_3/2, (CH₃)₂SiO, and/or (CH₃)₃SiO_1/2 units and having a specific gravity of 1.02 or greater has been found useful as an hydraulic fluid. The specific gravity of the hydraulic fluid allows for any water introduced into the system to collect as an upper layer above the hydraulic fluid where it can be removed easily. A particularly preferred methylpolysiloxane hydraulic fluid contains 0 to 10 mol percent (CH₃)₃SiO_1/2 units, 45-80 mol percent (CH₃)₂SiO units, and 20-45 CH₃SiO_3/2 units with a 1.65 to 1.80 CH₂/Si ratio.