At Peak Auto we specialize in brake service and repair. We use OEM brakes parts and Fluid including Textar, Zimmerman, and Pentosin. Brake fluid sounds like a simple part of the system, but what is the difference between DOT 3 and DOT 4. Also, what is DOT LV or Super DOT 4? Let us start with what brake fluid does. When you step on the brake pedal, the arm presses a piston in your brake master cylinder which pushes brake fluid to each caliper on your vehicle. The caliper has a least one piston that then expands and squeezes the brake pads against the brake rotor.
Squeezing the rotor creates friction which then in turns slows down the rotation of the rotor which is directly connected to your wheel/tire. Some vehicles have drums brakes in the rear (lower performance) and some vehicles have more than one piston per caliper (high performance). Most vehicles have ABS or anti-locking braking systems. This makes the braking a little more complicated to explain, and the more expensive your vehicle the more complicated the ABS system would be.
DOT 3 is most commonly found on American and Asian Vehicles. It has a lower boiling temperature (less performance) but does not attract moisture as much as it’s competition DOT 4. DOT 4 brake fluid has a higher boiling temperature (higher performance) but needs to be flushed and replaced more often. Some experts would argue that Brake Fluid is designed to attract moisture in order to retain the moisture and keep the water molecules away from important parts that could oxidize, corrode, or rust. We flush brake fluid to keep the other parts in the system protected so they will last longer. Calipers, ABS Pumps, and Master Cylinders can be quite expensive to replace, so it is preventative maintenance.
BMW (including Mini Cooper) Started using DOT 4 LV around 1999 and forward. The LV stands for Low Viscosity, which means more slippery. Audi and Volkswgen started using DOPT 4 LV around 2006. Mercedes Benz went a different route and focused on boiling temperature. When you use your brakes a lot, like when racing, everything gets hot, really hot. They came out with DOT 5 DOT 6 and Supper DOT. It seems like they are still looking for the magic but most of Mercedes Benz vehicles use SUPER DOT 4 which is supposed to have a higher boiling temperature than DOT 4. In investigating our German suppliers the DOT 4 Brake fluid that we use at Peak Auto has the same boiling temperature as the Super DOT 4 but does not attract water as much. When water is combined (through time) with the brake fluid it lowers the boiling temperature (not good).
It is recommended that you flush your braking system every 2 years. If your own a newer BMW, the vehicle keeps track of this maintenance item similar to keeping track of replacement on the you cabin air filters and engine air filter. At Peak Auto in Apex NC right next tot the Cary NC Auto Mall we are happy to explain in more detail when you bring your BMW, MINI Copper, Mercedes Benz, Audi, or Volkswagen in for service.