LOCOMOTIVE POWER BRAKE FLUID Dot-4 is made from high molecular weight polyalkylene glycol ethers and borate esters, to give a high boiling point fluid of DOT 4 quality. The formulation has been developed such that the vapor lock point can be sustained at a higher level than conventional glycol ether based fluids during the service life of the product. It contains inhibitors to prevent the corrosion of metallic brake components and to reduce oxidation at increased temperatures.