| abstract |
Disclosed is a synthetic lubricating oil comprising an ±-olefin (co)polymer defined by the following features (i) to (v): (i) said (co)polymer contains constituent units derived from (a) at least one monomer selected from ±-olefins of 8 to 20 carbon atoms in amounts of 90 to 100% by mol and contains constituent units derived from (b) ethylene in amounts of 0 to 10% by mol, (ii) the dynamic viscosity at 100°C is in the range of 8 to 500 mm 2 /s, (iii) the number-average molecular weight (Mn), as measured by gel permeation chromatography, is in the range of 500 to 15,000, (iv) said (co)polymer satisfies the following formulas (I) and (II): n A ¤ 24.0×Exp(-0.0239×K)(I) n B ¤ 0.0775×K(II) nwherein A is a content (%) of a (co)polymer having a molecular weight, as measured by gel permeation chromatography, of not more than 1,000, B is a content (%) of a (co)polymer having a molecular weight of not less than 20,000, and K is a dynamic viscosity (mm 2 /s) at 100°C, and (v) the molecular weight distribution (Mw/Mn) is in the range of 1.1 to 1.8. Also disclosed is a lubricating oil composition comprising the above-mentioned synthetic lubricating oil and a low-viscosity base oil. The synthetic lubricating oil and the lubricating oil composition have high thermal oxidation stability and are excellent in viscosity index, low-temperature viscosity properties and shear stability. |