There is provided a durable low-torque lubricating oil for bearings and fluid dynamic bearings, porous oil-impregnated bearings and hydrodynamic type porous oil-impregnated bearings suitable for use as bearings in small-sized spindle motors for information equipment. The lubricating oil composition comprising (A) a diester of a monovalent aliphatic alcohol containing 6-10 carbon atoms and a saturated aliphatic dicarboxylic acid containing 10 carbon atoms as base oil and (B) 3-20% by weight of a low-viscosity lubricating oil with a kinematic viscosity of less than 11 mm2/s at 40° C., a fluid dynamic pressure bearing unit or a porous oil-impregnated bearing unit containing said lubricating oil composition or a spindle motor provided with said bearing unit.