US Patent 7759293 Hydraulic oil composition for shock absorbers

Hydraulic oil compositions for shock absorbers comprises a lubricating base oil and at least one type of silicone oil selected from the group consisting of silicone oils with a kinematic viscosity at 25° C. of 10,000 to 350,000 mm2/s and fluorine-modified silicone oils with a kinematic viscosity at 25° C. of less than 10,000 mm2/s. The compositions may further comprise a viscosity index improver. The compositions can enhance the damping force and initial damping properties of a shock absorber and thus improve the ride comfort of an automobile equipped with such a shock absorber.