| abstract |
To provide a hydraulic fluid composition that can achieve both internal leakage prevention and pipe resistance reduction, and has high energy efficiency for the entire hydraulic system. SOLUTION: A lubricating base oil, an olefin copolymer having a number average molecular weight of 18000 or less, an α olefin having a number average molecular weight of 20000 or less, and a dicarboxylic acid ester, 0.2 to 40% by mass based on the total amount of the composition. And a hydraulic fluid composition comprising at least one copolymer selected from these copolymers. [Selection figure] None |