| 摘要 |
The object of the present invention is to provide a base oil for hydraulic oil suitably used for hydraulic systems having filters of which micropore diameter is 50µm or less, which is capable to improve the decrease of flow in a hydraulic pump at low temperature like -30°C or less and capable to normally operate the hydraulic systems. The invention also provides a hydraulic oil composition using the above base oil, especially a hydraulic oil composition suitably used for such as tractors, transmissions, and common systems thereof having the hydraulic systems. In order to achieve the object, provided is a base oil for hydraulic oil comprising mineral oil, wherein the mineral oil is defined by kinematic viscosity at 100°C: 1.5~6mm 2 /s, pour-point: -10°C or less, viscosity index: 100 or more, %C P : 70 or more, %C A : 2 or less, and aniline point: 106°C or more; and wherein, the mineral base oil is treated by catalytic dewaxing process and/or contains tertiary carbon atoms at a ratio of 7.4% or more to the total carbon atoms. |
