To provide the subject gear low in operational resistance, and to obtain a power steering fluid to be encapsulated therein.

This fluid-powered steering gear 10 for vehicle is equipped with a tubular housing 22, a power steering fluid 34 put in the housing 22, and a member (i.e., a rack 20) mobile relatively to the housing in response to the change in the fluid pressure in the housing. The power steering fluid 34 comprises a base oil and about 0.1-8wt.%, based on the base oil, of a grease.