On most vehicles, the brake fluid reservoir is attached to the master cylinder or brake booster, which is generally bolted to the firewall on the driver's side. The cap often has a dipstick that will indicate if the level is sufficient. If not, there should be markings on the side of the reservoir itself. Brake fluid is classified by DOT (Department of Transportation) type. The fluid reservoir cap should be stamped with the recommended fluid type. You can also consult your owner's manual or call your dealership's service department to identify the correct brake fluid type for your vehicle. Using the wrong fluid can severely compromise brake performance or cause damage to your brake system.
DOT 3 is the most commonly used type of brake fluid. It's amber in color and has a boiling point of 401潞 F when fresh and 284潞F when fully degraded. It is glycol-based and will quickly corrode paint, so if you spill it, clean it up quickly with soapy water and degreaser. DOT 4 fluid is mostly used in European cars, but it's becoming more widely used across the globe. It is also glycol-based but has a slightly higher boiling point than DOT 3 fluid. Mercedes and Volvo vehicles use a variant called DOT 4 Plus, and some BMWs use a version called DOT 4 Low Viscosity. There's also a variety called DOT 4 Racing Fluid, which has borate ester added to the glycol base. This聽raises the boiling point and gives it a bluish tint.聽