| 摘要 |
<p>The present invention provides a hydraulic oil composition comprising a base oil composed of a mineral oil (A) and/or synthetic oil (B) incorporated with 20 wt% or less, based on the whole composition, of one or more types of additives (C) including viscosity index improver and/or pour point depressant, and having a kinematic viscosity of 1 to 20 mm<2>/s at 100 DEG C, a viscosity index of 140 or more and a Brookfield viscosity of 2000 mPa•s or less at -40 DEG C, wherein the mineral oil (A) is a deeply dewaxed mineral oil (a) having a kinematic viscosity of 2 to 3 mm<2>/s at 100 DEG C, pour point of -30 DEG C or less and cloud point of -27.5 DEG C or less, or a mixed mineral oil of the deeply dewaxed mineral oil (a) and a low-viscosity mineral oil (b) having a kinematic viscosity of 1.0 to 6.0 mm<2>/s at 40 DEG C, and the synthetic oil (B) is a poly- alpha -olefin (c) having a kinematic viscosity of 1.5 to 45 mm<2>/s at 100 DEG C, and/or an ester compound (d) having a kinematic viscosity of 1.5 to 20 mm<2>/s at 100 DEG C and pour point of -30 DEG C or less.</p> |
