Synergistic lubricating oil composition containing a mixture of a nitro-substituted diarylamine and a diarylamine

A composition comprising a lubricating oil and an oil soluble synergistic mixture of antioxidants, said mixture comprising:

• a) from 0.1 to 10 weight percent of a first antioxidant according to formula I:
• wherein
• R1 is selected from the group consisting of alkyl from 3 to 24 carbon atoms, —NHR, —NRR where R is independently selected alkyl from 1 to 18 carbon atoms;
• R2 is hydrogen or alkyl from 1 to 20 carbon atoms;
• and
• b) from 0.1 to 5 weight percent of a second antioxidant selected from the formula
• wherein
• R3 and R4 are each independently hydrogen or alkyl from 1 to 20 carbon atoms;
• n is an integer from 1 to 3;
• R5 is selected from the group consisting of branched and straight chain hydrocarbyl radicals having from 3 to 24 carbon atoms selected from alkyl, alkoxy, aralkyl or alkaryl, or —NHR6, —NR6R7 where R6 and R7 are independently selected alkyl from 1 to 18 carbon atoms, or when R4 is positioned adjacent to R5 then R6 together with R4 can form a live- or six-membered heterocyclic ring.