The present invention relates to specific derivatives of dimer fatty acids, compositions comprising them and a method to reduce pour points.

An industrial oil composition contains a mineral or a synthetic oil as a base oil, and a neutral phosphite ester derivative represented by the following formula (B) and a 2,6-di-t-butylphenol derivative represented by the following formula (C) as antioxidants. In the formula (B), R.sup.b21 to R.sup.b24 each independently represent an aliphatic hydrocarbon group of 10 to 16 carbon atoms. In the formula (C), R.sup.c1 represents a straight-chain or a branched alkyl group of 1 to 12 carbon atoms. ##STR00001##