When should I replace it? Are brake fluids interchangeable?
To function correctly, the braking system not only depends on the maintenance of its mechanical and hydraulic components, but also on the condition of the brake fluid. The brake system relies on the incompressible nature of the brake fluid to efficiently transmit pressure from the brake pedal into hydraulic pressure to the brake caliper, for the brakes to apply in order to slow down or stop your vehicle.
In addition to this brake fluid must have a high boiling point to prevent boiling when exposed to high temperatures from braking.
If the brake fluid boils, it evaporates into vapour and vapour is compressible. If this happens the pedal will be compressing vapour and not transmitting the force to the brakes, which means slower response when braking that can prove fatal!
Brake fluid isalso required to keep the braking system lubricated and preserving its components against corrosion.
When should I replace it?
The recommended intervals for changing brake fluid are usually specified by the Manufacturer however may vary dependent on the type of fluid that is used.
99% of the car-park utilizes brake fluid that is glycol based and is highly hygroscopic, which means that they absorb moisture from the atmosphere. Due to its hygroscopic nature, brake fluid tends to absorb external moisture through the porosity of brake hoses. This deteriorates its condition , lowering the boiling point. Therefore brake fluid that has been in a vehicle for 3 years or longer has a considerably lower boiling point than brand new brake fluid from an unopened bottle. Having a low boiling point as mentioned previously leads to a reduced response when braking and, in some cases, pressing the brake pedal has no effect: called the Vapour Lock. Vapour Lock occurs when moisture in the brake system turns to steam when heated significantly, causing “compressibility” of the brake fluid Brake fluid should ideally be clear and clean. Dark and cloudy brake fluid indicates that it has accumulated impurities and that it’s time to be replaced.
Which brake fluid is correct for my vehicle?
Consult your vehicle's service manual to help choose the right DOT rated fluid for your vehicle. Using a DOT rated fluid other than what is recommended may cause improper brake operation.
Generally, glycol-based DOT 3, DOT 4 and DOT 4 Low viscosity brake fluids meet the technical requirements of 90% of cars on the road today.
Brembo DOT 4 brake fluid is suitable for use on most vehicles that use glycol based fluid, from the oldest to the most recent models, including those fitted with anti-lock braking systems (ABS).
For latest-generation cars, with ABS systems for stability or traction control systems (ESP, ASR, TCS, EBD), we recommend the Brembo DOT 4 LV (Low viscosity) brake fluid. Brembo DOT 4 LV (Low viscosity) brake fluid maintains uniform viscosity even at low temperatures. In these electronic systems, the fluid flows through control mechanisms where there are valves with very narrow passageways and it is vital for the fluid to maintain its viscosity, to flow smoothly for the precise and immediate transfer of pressure.
For drivers with high performance vehicles that produce even higher braking temperatures, Brembo recommend using DOT5.1 with higher boiling points however, owing to its characteristics, requires more detailed maintenance than DOT 4 fluids.
Are brake fluids interchangeable?
Car braking systems are manufactured to use a specific type of fluid. Therefore it is crucial that the vehicle should continue to use that particular type of fluid for the rest of its service life. This is crucial as the internal components of the braking system have been designed, selected and tested to operate with that particular fluid. Although DOT 3 and DOT 4 fluids are all glycol-based, the chemical composition of each type of fluid is different, so it will have a different effect on the system. To ensure that the system works as it should, it is imperative to keep using the exact brake fluid recommended by the manufacturer.
To find out more
What brake fluid does and why its maintenance is important: