FLUID COMPOSITION FOR POWER STEERING

摘要

PURPOSE:To obtain the subject fluid composition capable of suppressing shoe sound by cavitation at squeezing part of a direction changeover valve by adding an olefin copolymer or polyisobutylene to base oil having a specific viscosity at a definite ratio. CONSTITUTION:The objective low-cost fluid composition obtained by adding (B) an olefin copolymer such as ethylene-propylene copolymer or polyisobutylene having >=100000 weight average molecular weight to mineral oil or synthetic oil such as a poly-alpha-olefin being 1.5-70cst dynamic viscosity at 100 deg.C in a polymer concentration of >=0.25wt.%.