To obtain a lubricant composition excellent in storage stability at a low temperature and in friction reducing effect, and useful as an automobile engine oil, a gear oil, an agricultural machine oil, or the like, by mixing a specific boric acid ester with a specific basal oil to dilute the ester.
(A) A boric acid ester of a diol compound mainly composed of an alkane-1,2-diol (e.g. hexadecane-1,2-diol) of formula I (R1 is a 12-30C alkyl) in which the oligomer content satisfies the equation 0 wt.% < oligomer content < 30 wt.% and/or a boric acid ester of a diol compound mainly composed of a glycerol monoalkyl ether (e.g. glycerol monohexadecanyl ether) of formula II (R2 is a 14-30C alkyl) in which the oligomer content satisfies the equation 0 wt.% < oligomer content < 30 wt.%, is mixed with (B) a basal oil having a viscosity index of 80-150 (e.g. a paraffin-based hydrogenated, decomposed and refined mineral oil), preferably at a ratio of 0.01-2.0 wt.% of the component A based on the total amount of the composition to dilute it.
TAKAHASHI KOJI
KAWAHARA YASUYUKI
TOMIZAWA HIROTAKA
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