Abstract: Disclosed are stabilized lubricating oil compositions with improved oxidative performance. These lubricating oil compositions contain certain phenolic antioxidants, in combination with other antioxidants, which contribute to the improved performance. These certain phenolic antioxidants are defined in formula (I), wherein, R1 is alkyl of 1 to 4 carbon atoms, n is 1 to 4, R2 is H or R3, R3 is —(CH2)x—COOR4 where x is 1 to 10, R4 is straight or branched chain alkyl of 1 to 24 carbon atoms or E, when n is 1, E is straight or branched chain alkyl of 1 to 24 carbon atoms; when n is 2, E is straight or branched chain alkylene of 2 to 12 carbon atoms or said alkylene interrupted by one to five O or S atoms; when n is 3, E is a straight or branched chain alkanetriyl of 3 to 6 carbon atoms; and when n is 4, E is pentaerthyrityl.

Abstract: The present invention discloses a process for stabilizing polyolefin compositions against the deleterious effects of melt processing, heat aging and exposure to combustion products of natural gas, which process comprises incorporating or applying to a polyolefin an effective stabilizing amount of a tris-(mono-alkyl)phenyl phosphite ester of the formula I, or a mixture of phosphite esters of formula I, where each R is the same or different and is straight or branched chain alkyl of from 1 to 8 carbon atoms, and where said phosphite ester or phosphite ester mixture is in the liquid state at 25° C. and 1 atm of pressure. Also disclosed is a stabilized composition comprising polyolefin and a present phosphite ester or phosphite ester mixture as well as certain mixtures of tris-(mono-alkyl)phenyl phosphite. The present liquid phosphite ester stabilizers are especially compatible with low density polyethylene.