Abstract: An oil-soluble polyester having a weight average molecular weight of 10,000 to 1 000,000, which is a polycondensate prepared by polycondensing the following ingredients (A), (B) and (C):(A) a divalent higher carboxylic acid ingredient,(B) a divalent alcohol ingredient comprising a glycol represented by the following formula:HO--CH.sub.2 --CR.sup.1 R.sup.2 --CH.sub.2 --OHwherein R.sup.1 and R.sup.2 represent a alkyl group, and the sum of carbon numbers in R.sup.1 and R.sup.2 is at least three, and(C) 0.1 to 15% by mole, based on the total of ingredients (A) and (B), of at least one multi-valent ingredient selected from a carboxylic acid with a valency of at least three and an alcohol with a valency of at least three. This oil-soluble polyester is useful as an additive for a lubricating oil.

Abstract: An oil-soluble polyester having a weight average molecular weight of 10,000 to 1,000,000, which is a polycondensate prepared by polycondensing the following ingredients (A) and (B): (A) a dicarboxylic acid ingredient, and (B) a diol ingredient comprising (i) a hindered glycol represented by the following formula: HO--CH.sub.2 --CR.sup.1 R.sup.2 --CH.sub.2 --OH wherein R.sup.1 and R.sup.2 independently represent a linear or branched alkyl group, and (ii) an alkylene glycol having at least 4 carbon atoms in the main chain. This oil-soluble polyester is useful as an additive for a lubricating oil.