HYDRAULIC FLUID

The present invention provides a hydraulic fluid comprising:(a) 40 to 2000 ppm by weight in terms of nitrogen content of a corrosion inhibiting agent which is one or more compounds of formula (I):and/or tribologically acceptable salts thereof, wherein in formula (I):each R1 is independently a hydrocarbyl group comprising 1 to 10 carbon atoms,x is 0 to 4,each of R2 and R3 is independently hydrogen or a hydrocarbyl group comprising 1 to 20 carbon atoms,R4 is -NR5R6 or -OR7,each of R5 and R6 is independently an aryl group comprising 6 to 14 carbon atoms, optionally substituted with one or more hydrocarbyl groups comprising 1 to 20 carbon atoms,R7 is a hydrocarbyl group comprising 1 to 20 carbon atoms, andin each of said hydrocarbyl groups containing 2 or more carbon atoms, the carbon chain may, independently, optionally be interrupted by one or more ether groups;(b) 0.1 to 1% by weight of an ashless dispersant; and(c) a major amount of a base oil.