Comma BF51L Dot 5.1 Synthetic Brake Fluid, 1 Liter

Product Information

Hydragas and Hydrolastic suspension were a widely used form of hydropneumatic suspension, designed by Alex Moulton, and used on British Leyland cars from the 1960s. This system was not engine-driven and did not involve the braking system. DOT 4 brake fluid absorbs moisture via the brake lines. As you keep pressing the brake pedal, the fluid in the system warms up. Source: Pixabay

Glycol-ether (DOT 3, 4, and 5.1) brake fluids are hygroscopic (water absorbing), which means they absorb moisture from the atmosphere under normal humidity levels. Non-hygroscopic fluids (e.g. silicone/DOT 5 and mineral oil based formulations), are hydrophobic, and can maintain an acceptable boiling point over the fluid's service life. Ideally, silicone fluid should be used only to fill non-ABS systems that have not been previously filled with glycol based fluid. Any system that has used glycol-based fluid (DOT 3/4/5.1) will contain moisture; glycol fluid disperses the moisture throughout the system and contains corrosion inhibitors. Silicone fluid does not allow moisture to enter the system, but does not disperse any that is already there, either. A system filled from dry with silicone fluid does not require the fluid to be changed at intervals, only when the system has been disturbed for a component repair or renewal. The United States armed forces have standardised on silicone brake fluid since the 1990s. Silicone fluid is used extensively in cold climates, particularly in Russia and Finland. The International Standards Organisation has published its standard ISO 4925, defining classes 3, 4, and 5, as well as class 5.1, class 6 [2] and class 7 [3] [4] reflecting progressively higher performance for brake fluids. Do NOT use DOT 3 in your motorcyclesince its boiling point is too low. The brake system might not work properly with DOT 3.

Because of the slow adoption of the DOT 5, something had to be done. A ton of carmakers didn’t want to swap to this type of brake fluid so there needed something to be done. DOT 5 is mainly used for classic cars. Since they do not run ABS and it is a really good application for these types of vehicles. In addition to this, this type of fluid prevents rust in the brake lines and this makes it perfect for cars intended for long-term storage. So, if you have a classic motor, this is the right fluid for you. What Vehicles Use DOT 5 Brake Fluid It has a completely different chemical structure since it’s made out of silicone and it does not resemble the glycol-based compounds in any way possible. This is why manufacturers gave it a distinctive purple color to make it different so people would not mix these two types of fluid. Before we dive into more complex topics such as the DOT 5 brake fluid, let’s first take a look at the basics of the brake fluid and also learn what this DOT abbreviation means in the first place. Knowing this will be a good starting point for beginners who are not into cars and want to learn the basic stuff. To make the choice easier, brake fluids are classified into categories: DOT 3, DOT 4, DOT5, and DOT 5.1.

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.The disadvantage of mineral oil is that it’s unregulated and as a result, not all mineral oils are created equal. While on the other hand DOT 3 is not interchangeable with DOT 5 brake fluid. These two are completely different and do not overlap. So, if your car is not certified for DOT 5, you should avoid using it and instead use the 5.1 fluid instead. This will guarantee that you get the best performance for your money. 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.

The effects of this water content over time are better illustrated by the graph below. This graph is taken from Shell and gives an overview of the declining effect water content has on its range of DOT 3 and DOT 4 brake fluids. This means that it is rather different from the regular hydraulic fluid that is known as ATF or transmission fluid. Since DOT 3 is glycol based, it absorbs moisture easily as well. As a result, DOT 3 brake fluid accumulates around 3% of water in it in a year. AN EXPLANATION OF BRAKE AND CLUTCH FLUIDS". Xpowerforums.com. Archived from the original on 2008-11-04 . Retrieved 2015-05-26.

Can I mix and match fluids?

Brake fluid is only one of several vital components which enable hydraulic brake systems to work effectively. Its job is to transfer the input forces you create at the master cylinder (lever) to the caliper pistons. This is possible as fluids are generally incompressible.