A fluid power steering gear (10) comprises a housing (16). A power steering fluid (34) is disposed within the housing (16). A seal (50) contains the power steering fluid (34) within said housing (16). A member (20) extends through the housing (16) and the seal (50). The member (20) is movable relative to the housing (16) and the seal (50) in response to a change in the fluid pressure in the housing (16). The power steering fluid (34) comprises a base oil and a metal-free lubricant additive. The metal-free lubricant additive is soluble in the base oil and modifies the interfacial surface tension between the base oil and the member (20) and the base oil and the seal (50). The weight percent of the metal-free lubricant additive is about 0.1% to about 5.0%, by weight of the power steering fluid (34).