| abstract |
The present invention provides a hydraulic oil composition comprising: a lubricating base oil; and 0.2 to 40% by mass, based on a total amount of the hydraulic oil composition, of at least one copolymer selected from olefin copolymers having a number-average molecular weight of 18000 or lower and copolymers of an α-olefin and a dicarboxylic ester, having a number-average molecular weight of 20000 or lower. |