Lubricating oil composition is provided. The composition includes several components including a base oil, a primary antioxidant including alkylated diphenylamines having an alkyl group derived from propylene tetramers, and a carboxylate detergent.

A substantially zinc-free hydraulic fluid is provided. The substantially zinc-free hydraulic fluid contains a calcium detergent, an ashless antioxidant, and a metal-free phosphorous containing anti-wear agent. In one embodiment, the fluid contains at least 90 weight percent of a base oil having less than 500 ppm sulfur, a calcium detergent in an amount to deliver 5 ppm to 200 ppm calcium to the fluid, at least one metal-free phosphorus containing anti-wear agent to provide 10 ppm to 150 ppm phosphorous, and one or more ashless antioxidants. A method of lubricating a hydraulic system with the substantially zinc-free fluid is also provided.

A lubricant composition comprising an oil-soluble polyalkylene glycol; an ester compound selected from the group of natural esters and synthetic esters, and combinations thereof; and an additive mixture comprising an antioxidant and an anticorrosive, wherein the anticorrosive is selected from neutral alkali metal and alkaline earth metal salts of sulfonic acids, carboxylic acids, naphthoic acids, naphthenic acids, benzoic acids and phosphoric acids, and derivatives and combinations thereof.

Lubricating oil composition is provided. The composition includes several components including a major amount of a base oil, a mixture of alkylated diphenylamines having a weight ratio of mono-alkylated diphenylamine to di-alkylated diphenylamine ranging from 0.6 to 4.0, and a molybdenum or sulfur additive that provides synergistic enhancement of oxidation stability in combination with the mixture of alkylated diphenylamines.