Oil compositions useful in hydraulic fluids

The present invention includes a composition which comprises a major amount of an oil of lubricating viscosity and a minor amount effective to inhibit metal corrosion of a soluble additive mixture comprising (A) at least one amide compound of a mono- or polycarboxylic acid or reactive derivative thereof; and (B) at least about 0.1 mole of at least one amine per mole of amide, provided that when (A) is an amide of a dicarboxylic acid and the amine is an alkanol amine, the mixture contains more than 0.5 equivalent of the amine (B) per equivalent of amide (A). The compositions of the invention exhibit improved corrosion-inhibiting properties and the compositions are useful in a variety of lubrication applications. In particular the compositions are useful as hydraulic fluids.