The composition of the brake fluid includes a base consisting of polyglycols and their esters or silicones, and additives. Additives should protect metal parts of the brake system from corrosion.
Brake fluids are produced according to J1703, ISO standards (DIN) 4925 and FMVSS 116. The brake fluid class for a particular vehicle is determined by its manufacturer.
The manufacturer must indicate the basis of the brake fluid on the packaging. Domestic and imported liquids of classes DOT 3, DOT 4 and DOT 5.1 can be mixed in any proportions. Liquids have shades from light yellow to light brown.
Warning! DOT 5 brake fluids are silicone based and are not compatible with polyglycol fluids. Silicone-based liquids are dark red in color.