Comma BF51L Dot 5.1 Synthetic Brake Fluid, 1 Liter

Product Information

Do not mix brake fluid types.A DOT 5 is strictly not allowed to mix with any other fluids. While DOT 3 and DOT 4 are technically mixable, it is still NOT recommended since they can react badly and corrode the brake system. Compared to racing fluids, this fluid’s dry boiling temperature is about 270° C and 190° C wet. DOT 5.1 has the added benefit of being adaptable to a variety of rubber compositions. DOT 3 and DOT 4 are also compatible with it. Another thing to add is that all the types of fluids are rather the same by structure except the DOT 5 brake fluid. And later on in this article, we are going to explain why is this the case and how they differentiate. Types Of Brake Fluid?

Let's take a look at the minimum boiling temperatures of DOT brake fluid as specified by the Department of Transportation. If you need to use DOT 3 or even DOT 5.1. Consider flushing your old brake fluid completely before adding another type of brake fluid to your brake system reservoir. The Dot 4 brake fluid offers the viscosity of 1800 at 40 degrees Fahrenheit. Although DOT 5.1 has a better lifespan and is compatible with motorcycles, most motorcycle braking systems are designed for DOT 4. The chief disadvantage of DOT fluid is that it is hygroscopic, which means it absorbs water, unlike mineral oil. Make sure to cover any areas DOT fluid could leak onto with a rag because it’s corrosive. Matthew Allen / Immediate Media

To reduce large quantities of wasted brake fluid, use DOT fluid from smaller 100ml bottles. 100ml is enough to bleed a set of brakes (front and rear) 2-3 times. When brake fluid absorbs enough heat it boils and vaporises. It turns from a fluid into a gas. This gas can lead to complete brake failure in hydraulic systems. Suddenly the incompressible nature of the brake fluid, which produces the firm lever feel that we know and trust, has disappeared due to the introduction of compressible gasses in the brake system. The Dry Boiling Point of brake fluid refers to the boiling temperature of fresh, new brake fluid from an unopened container. Whereas the Wet Boiling Point is defined as the temperature DOT brake fluid will begin to boil after it has absorbed 3.7% water by volume. DOT brake fluid will reach this level of water volume after roughly 2 years of service, which is why it is advisable to renew your brake fluid every year. It seems like everyone should want to be using DOT 5 brake fluid since it has the highest boiling point and absorbs no moisture and won't react with everything else in your vehicle. And while that does make it seem good, there are some issues with it as well.

Silicone DOT 5, as we mentioned earlier, is not compatible with any of the other DOT fluids, nor is it able to be mixed with Mineral Oil brake fluid. Since there is no hydraulic mountain bike brakes using DOT 5 fluid we won't worry too much about it. The main thing to remember is it should never be confused with DOT 5.1 as they are fundamentally different brake fluids.

What is mineral oil?

DOT 5.1 is not a revision of DOT 5, as is commonly believed. DOT 5.1 is a mixture of borate ester and polyalkylene glycol ether, a silicone-based product. But still, you should not mix them together. When it comes to switching from DOT 3 to DOT 4 we would recommend you do perform a complete flush of the system and add completely new fluid. Now let’s cover some of the pros and cons of the DOT 5. Knowing these things is really important to determine if you want this type of fluid on your car.