This standard specifies requirements for fluids for use in hydraulic brake systems of motor vehicles@ containers for these fluids@ and labeling of the containers. Purpose. The purpose of this standard is to reduce failures in the hydraulic braking systems of motor vehicles which may occur because of the manufacture or use of improper or contaminated fluid. Application. This standard applies to all fluid for use in hydraulic brake systems of motor vehicles. In addition@ S5.3 applies to passenger cars@ multipurpose passenger vehicles@ trucks@ buses@ trailers@ and motorcycles.