| abstract |
PURPOSE:To prepare a hydraulic fluid compsn. excellent in oxidation stability, heat stability and other performances by using a mineral oil having specified compsn. and characteristics as a main ingredient of the base oil. CONSTITUTION:A mineral oil of a specified compsn. (total arom. content of 2-15% wt.; total content of isoparaffin and monocyclic naphthene of 60% wt. or above; alkylbenzene content in total arom. components of 30% wt. or above; and tri- and tetra-cyclic arom. content in the total arom. components of 4% wt. or below) having a viscosity index of 105 or above and a pour point of -10 deg.C or below is used as the main ingredient of the base oil. |