Which brake fluid for my car? Looking to change your brake fluid, but unsure which brake fluid you should use for your car? Is it DOT4, DOT3 or perhaps you’re unfamiliar with the different types of brake fluid? Learn what brake fluid is, how often it should be changed and how to work out which brake fluid to use for your own vehicle now from our helpful guide.
What is brake fluid?
Brake fluid, also known as hydraulic fluid, is vital for moving parts of your braking system. Brake fluid applies hydraulic pressure to the callipers in the system when you press your brake pedal, working under very high pressure. The pads then work with the brake discs, slowing your car down, and then brings it to a stop.
Without brake fluid, you would not be able to use your car brakes at all – so it’s important your brake fluid is topped up in order for you to use your vehicle effectively.
Understanding the different types of brake fluid
Brake fluid is referred to by “DOT” and a number. DOT stands for Department of Transportation, the federal agency responsible for regulating brake fluid specifications for vehicles in the United States. These regulations ensure standard product quality for everyone’s safety.
Each number has a higher boiling point. Most vehicles in the USA take DOT3 or 4 which are amber in color, like a light beer. They are glycol-based and will absorb moisture out of the air (hygroscopic is the technical term). Thus, you’ll want to keep the top of your bottle tight and don’t open the master cylinder reservoir unless needed.
Most master cylinder reservoirs are clear for this reason. Because of its affinity to absorb moisture and the heat generated during braking, brake fluid performance will degrade over time. It will become acidic, promoting the formation of rust and debris in the system, which can clog valves in an expensive ABS system.
By far, DOT 3 is the most popular. It’s been in use for a very long time. Fresh DOT 3 has a boiling point of 401 degrees Fahrenheit; fully degraded, it drops to 284 degrees Fahrenheit. This makes your brake fluid much more likely to boil. Braking hard, going downhill for a long period, towing, or racing can speed up this process.
Since DOT 3 is highly corrosive, great care should be taken. It will remove paint and should be cleaned up immediately using soap and water or a simple degreaser.
DOT 4 is used primarily by European car manufacturers, but it is beginning to be used more widely by vehicle manufacturers elsewhere. Although there are different types of DOT 4 brake fluid, it has a higher boiling point than DOT 3. These boiling points start at 446 degrees Fahrenheit. Additional additives in DOT 4 help reduce the acids that can form from moisture.
While DOT 3 and 4 are technically intermixable, it is not recommended. DOT 4 is twice the cost of DOT 3 and for most, there’s little benefit to switching. There are several different types of DOT 4 so be certain you use the correct type.
DOT 4 is used in some euro and domestic vehicles. DOT 4 Plus is used in Mercedes and Volvo. DOT 4 Low Viscosity is used in some BMW models. Finally, DOT 4 Racing usually has an added blue color.
DOT 5 is a silicone-based brake fluid and has a very high boiling point of 500 degrees Fahrenheit. Usually, it has a purple color to differentiate from the amber color of DOT 3 and 4. It doesn’t absorb water quite like the glycol-based brake fluids, but it does become foamy and the air bubbles are far more difficult to bleed out. This is why DOT 5 is not recommended for ABS systems.
DOT 5 is not able to be mixed with any other fluid and is 4x more expensive than DOT 3.
DOT 5.1 is a glycol-based brake fluid with a boiling point similar to DOT 4 racing brake fluids. Usually clear to amber in color. While it is technically intermixable with DOT 3 or 4, it is not recommended. DOT 5.1 is around 14x more expensive than DOT 3.
How often to change brake fluid?
Typically, it’s recommended by vehicle manufacturers that your brake fluid should be changed at least once every two years. This is to maintain both the quality and the lifespan of the brakes on your vehicle.
However, the frequency of how often you change brake fluid can often vary between different vehicle manufacturers so, if you’re not sure, consult your manufacturer or your vehicle handbook.
Which brake fluid for my car?
There are multiple different types of brake fluid that can be used for your vehicle. However, these are grouped into two headings:
- Glycol based – this includes brake fluids such as DOT3, DOT4 and Super DOT4.
- Silicone based – an example of a silicone-based brake fluid is DOT5.
Typically, most vehicles use DOT4 – however, to find out which brake fluid you need to use for your vehicle, you will need to consult your vehicle handbook.
The reference to ‘dots’ in the different types of brake fluid refer to the fluid’s boiling point – typically, the lower the ‘DOT’ number (for example, DOT3), the lower the fluid’s boiling point. How you use your vehicle will then determine which level of ‘DOT’ you’ll need for your brake fluid.
A high performance driven car; one used for race driving or driving around rural hilly areas, for example, will likely require a brake fluid with a higher ‘DOT rating, due to its lower boiling point.
What does brake fluid do?
Playing a crucial role in the braking process, brake fluid helps transfer the movement and force created when you press down on the brake pedal. Extreme heat is generated when braking. This high heat can cause moisture to condense in the brake hydraulic system.
The brake fluid absorbs this moisture and prevents it from boiling and causing brake failure. In addition, the brake fluid serves as a lubricant for all movable parts and prevents corrosion. It must remain fluid in all temperatures.
Brake fluid helps transfer the movement and force created when you press down on the brake pedal.
Adding brake fluid is usually not part of routine vehicle maintenance. Low brake fluid typically means that your brake pads are worn and will soon need to be changed.
If you notice a sudden drop in the brake fluid level, it could indicate a problem with your brake system or that you simply need to change your brakes. Have a mechanic check your brakes if you are unsure.
What happens if your brake fluid is low?
Brake fluid works hard every day to keep you safe on the road. However, brake fluid is not something most people think about until something starts going wrong. Over time, it can become contaminated, depleted, or burnt out, which prevents proper brake function.
Common signs that you have a brake fluid problem include:
The ABS light comes on
One of the basic indicators that brake fluid is low is when the Anti-Lock Braking System (ABS) light on a vehicle’s dashboard illuminates. While not all vehicles, particularly older models, have ABS lights, newer vehicles generally come equipped with this feature to inform drivers of a potential problem.
Brake pads not functioning properly
When brake fluid is low or dirty, it cannot depress brake pads as efficiently as it should. This can lead to uneven wear and damage to brake pads, causing squealing, squeaking, or grinding noises when the brakes are engaged.
Strange noises when braking
Braking systems that don’t have enough fluid in them, or have old fluid, will begin to make noise. When this occurs, it is important to have the brakes checked as soon as possible.
Problems with the brake pedal
When brake fluid is low, or needs to be replaced, a driver may notice that the brake pedal doesn’t respond like it used to. If the pedal feels firmer than usual, the fluid could be contaminated. If the pedal feels soft, bouncy, and/or spongy when the pedal is pressed down, it can be a sign that the brake fluid is getting low.
Smoke or burning smells
Overheating brakes can emit smoke or burning smells after prolonged use. If this occurs, drivers should pull over as soon as possible to allow the brakes to cool. If a vehicle continues to be driven in this condition, the overheated fluid can cause brake failure, preventing the ability to stop.
Can i drive without brake fluid?
No. Brake fluid is essential to safe driving. The pressure applied to a brake pedal is transferred through the brake lines via fluid that pushes against the brake pads. Without this essential fluid, brakes won’t work.
Which brake fluid is best for powerstop brakes?
PowerStop components are only compatible with glycol-based DOT 3, 4, and 5.1 brake fluids. Most vehicles in the United States use DOT 3 and many European vehicles use DOT 4. Check your vehicle’s owner’s manual to find the factory-recommended brake fluid if you aren’t sure.
How do I know what brake fluid to use?
The best way identify what type of brake fluid your car needs is to check your owner’s manual. You can also check the master cylinder reservoir cap to identify the type of brake fluid used in your vehicle.
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