DOT 5

DOT 5

DOT 5 is one of several designations of automotive hydraulic brake fluid, denoting a particular mixture of chemicals imparting specified ranges of boiling point.

DOT 5 is a silicone-based brake fluid (contains at least 70% by weight of a diorgano polysiloxane).

Unlike polyethylene glycol based fluids, it is hydrophobic. Its chief advantage over other forms of brake fluid is that silicone exhibits a more stable viscosity index in extreme temperatures. It is widely used in the antique automobile arena as well as it does not damage paint.

Using DOT 5 in a DOT 3 or DOT 4 system without proper flushing will cause damage to the seals and cause brake failure. DOT 5 brake fluid is not compatible with anti-lock brake systems. DOT 5 brake fluid absorbs a small amount of air requiring care when bleeding the system of air.