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What is Brake Fluid?

Brake fluid is a hydraulic substance that helps convert force into pressure when a driver steps on the brake pedal. This conversion causes the brake pads to clamp down on the vehicle's brake rotors, which slows down or stops a car. Since a vehicle's braking system experiences high temperatures, brake fluid is made with very high wet and dry boiling points to avoid vaporization. Its wet boiling point, which is when the fluid boils once moisture is absorbed, is lower than the dry boiling point. There are four main types of brake fluid designated by the U.S. Department of Transportation, each with designated boiling points and fluid bases and for specific vehicles.

Types of brake fluid

Brake Fluid Type

Wet Boiling Point

Dry Boiling Point




284° F401° FPolyethylene glycolCars, pickup trucks and SUVs


311° F446° FPolyethylene glycolCars, pickup trucks and SUVs


356° F500° FSiliconeCars without anti-lock brake systems

DOT 5.1

356° F500° FPolyethylene glycolHigh performance or racing vehicles