Wis. Stat. § 347.37: Brake fluid, sale regulation.

(1) After January 1, 1960, no hydraulic brake fluid for use in motor vehicles shall be sold in this state if such brake fluid is below the minimum standard of specifications established by the society of automotive engineers for heavy duty type brake fluid No. 70R1 or a later designator for an improved product.

(2) All manufacturers of brake fluids selling such fluids in Wisconsin shall state on the immediate containers in which such fluid is packaged that the fluid therein meets or exceeds the specifications under sub. (1).