Abstract: Hydraulic oil for use in construction machinery, wherein the hydraulic oil comprises a poly(meth)acrylate of weight average molecular weight in the range of from 30,000 to 100,000 in a highly refined base oil but does not incorporate an oiliness agent, and wherein the kinetic viscosity at 60° C. is in the range of from 25 to 60 mm{hacek over ( )}/s, the kinetic viscosity at 80° C. is in the range of from 15 to 34 mm{hacek over ( )}/s, the viscosity index is in the range of from 200 to 220, and the low temperature cranking viscosity at 25° C. is in the range of from 1000 to 8000 mPa·s. The hydraulic oil of the present invention not only has a high kinetic viscosity in the high-temperature domain even though the incorporation of an oiliness agent is omitted, and can thereby effect satisfactory operation efficiently and which has excellent braking characteristics, but which also has a low viscosity in the low-temperature domain and so has excellent low-temperature performance.

Abstract: The present invention involves the addition of an aspartic acid derivative and a fatty acid ester of a polyhydric alcohol to a base oil of, e.g., mineral oil or synthetic oil type. By including these additives, a lubricating oil composition having excellent rust-preventing properties, reduced friction coefficient and excellent energy-saving properties and so being suitable for industrial lubricating oils can be obtained. Also, by further adding an epoxy compound and by adding also a fatty acid amine, it is possible to obtain a lubricating oil composition even more endowed with rust-preventing properties and energy-saving properties.

Abstract: A lubricating oil composition is provided containing a base oil having a kinematic viscosity at 40° C. in the range of from 2 to 20 mm2/s and a viscosity index of 50 or more and a polymethacrylate, wherein the lubricating oil composition has a kinematic viscosity at 40° C. in the range of from 22 to 95 mm2/s; a kinematic viscosity at 100° C. in the range of from 10 to 30 mm2/s; a pour point of ?10° C. or less; a CCS viscosity at ?20 ° C. of 2500 mPas or less; and a flash point of 140° C. or more.