The brake liquid is perhaps the most important fluid in your vehicle. If the level of brake fluid is too low or has already lost its properties it can put both your safety and that of the passengers at serious risk.
With that said, how can you tell if the brake fluid has already lost its properties and therefore your vehicle requires a brake fluid change? Moreover, in case you need to service your brake system, what would be the right brake fluid to use? DOT 3, DOT 4, DOT 5.1?
In this article, we will answer these and other key questions concerning this important topic.
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Comparison of the Best Brake Fluids
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Is All Brake Fluid The Same?
No, all brake fluids are not the same. In fact, there are significant differences regarding their properties, their useful life, and the type of application for which they are recommended. It should be noted, that the correct type of brake fluid to use in your vehicle will be written on your brake fluid resevoir cap and also in the service manual.Below, we analyze the main types of brake fluid, namely:
DOT 3
It is the most common type of brake fluid, ideal for pre-2010 daily driving vehicles. It has the lowest boiling points, 205 °C (401 °F) dry boiling point and 140 °C (284 °F) wet boiling point.
DOT 4
Similar in composition to DOT 3 but with additives that enhance its properties to reach 230 °C (446 °F) dry boiling point and 155 °C (311 °F) wet boiling point. This fluid is designed for applications that require more robust brake systems such as modem passenger cars, trucks, and full-size SUVs. A disadvantage of this liquid is that it absorbs water more quickly, so it has to be replaced more frequently than DOT 3 fluid.
Super DOT 4
Exceeds the properties required by the DOT 4 standard, hence its name. It can reach dry boiling points over 340 °C (644 °F) which makes it ideal for racing applications and high-performance vehicles. Moreover, in many cases, this fluid also has enhanced hygroscopic properties which makes it less prone to absorb water.
DOT 5.1
It is in many ways similar to DOT 3 and DOT 4 fluids, but its formula allows it to have the same minimum wet and dry boiling points as DOT 5. Additionally, this type of liquid is less viscous which is required by the ABS and ESC systems of newer vehicles.
DOT 5
Even though its notation suggests that it is a less advanced brake fluid than DOT 5.1, the reality is quite the opposite. This type of brake fluid is silicone-based and does not absorb moisture like DOT 3, 4, or 5.1 fluids. It is extremely expensive and should only be used on vehicles that explicitly specify it.
Buying Brake Fluid: What to Look For
Choosing the best brake fluid depends on several aspects. Let’s review some of them.
Hygroscopic Properties
Have to do with the ability of the brake fluid to absorb water. In the case of DOT 3, 4, and 5.1 brake fluids, their hygroscopic properties largely determine their service interval as it affects the fluid’s compressibility.
Compressibility
Under normal conditions, all liquids have low compressibility which allows them to transfer energy in hydraulic systems. However, as brake fluid absorbs moisture its properties change. Since water has a lower boiling point than brake fluid, it can easily boil, creating bubbles in the system.
Unlike liquids, vapors are compressible, so these bubbles can dramatically increase the compressibility of the fluid, making it less effective. Hence the importance of the hygroscopic properties of brake fluid.
Viscosity
In very cold environments or vehicles with the latest generation ABS and ESP systems, the viscosity becomes a determining factor. That’s why most manufacturers require brake fluids with low viscosity levels.
Dry Boiling Point
This is one of the most important factors to consider. The “dry” boiling point is the temperature at which the fluid boils when it is in a pure state (without moisture). The higher the boiling point, the better the fluid’s ability to withstand the high temperatures generated by the brake system.
Wet Boiling Point
It is the boiling point when the brake fluid has a water content of approximately 4% by volume. Like the dry boiling point, the higher it is, the more beneficial for the brake system. The wet boiling point gives you an idea of how often you should change the fluid (the lower the boiling point, the more often you should change it).
Review of the Best Brake Fluids
Ready to explore the best brake fluids on the market? In this section, we will review each of the types of brake fluid available, as well as their most common applications.
Best Overall:Pentosin DOT4 LV Brake Fluid
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PROS
- Exceeds DOT 4 dry and wet boiling points
- Extremely low viscosity at cold temperatures
- Safe to use on vehicles that require DOT 4 fluid
- Ideal for newer vehicles fitted with next-gen ESP, ASR, and ABS systems
- Superior hygroscopic properties give it incredible resistance to absorbing and retaining water
CONS
- More expensive than most other DOT 4 brake fluid
- Due to its lower viscosity, it can give pre-2010 vehicles an overly soft pedal feel
What Are This Fluids Specs?
- Color: clear/yellow
- 170 °C (338 °F) wet boiling point (+15 °C)
- Meets FMVSS 116 DOT 4, ISO 4925 Class 6, SAE J1704 specifications