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What color is brake fluid?

What color is brake fluid?

The color of brake fluid is an important indicator of its health and safety. Not all brake fluid is the same color and can change over time. It's important to keep an eye on the color of your brake fluid to keep you informed about the condition of your brake system and alert you to any deterioration.

Brake Fluid Colors

Black brake fluid

Brake fluid can turn black due to contamination from particles and residue that naturally build up in the brake system over time. These particles can come from normal wear and tear on brake system components such as pads, rotors, calipers, pistons, or seals.

Brake fluid darkens due to corrosion of internal brake system components, which can release metal particles into the brake fluid. Corrosion can be caused by water contamination of the brake fluid or by the use of a brake fluid that is incompatible with the brake system materials.

In either case, the presence of particles in the brake fluid can lead to loss of brake performance and even complete failure of the brake system.

Green Brake Fluid

When brake fluid turns green, it may indicate contamination by moisture or other substances.

More specifically, a green color can indicate the presence of copper in the brake fluid. This can occur if copper brake lines are used in the brake system, which can cause copper oxidation and lead to the formation of green particles in the brake fluid.

Brown Brake Fluid

Brake fluid turns brown when it begins to deteriorate and contaminants build up in the fluid. If the brake fluid is not changed regularly, these contaminants can build up and reduce the efficiency of the brake system.

Red brake fluid

Brake fluid can turn red for a number of reasons, but the most common is the presence of a red dye added by the manufacturer. Brake fluid is often dyed for ease of identification and to distinguish brake fluid from other automotive fluids. This technique also facilitates brake fluid quality control by making it easier to see if there are any contaminants or impurities in the fluid.

In another case, if brake fluid turns red without any added dye, it may be a sign of contamination from water or engine oil. Water can enter the brake system from moisture in the ambient air or from a leak in the system. Engine oil can also enter the brake system through a leak in the cylinder head gasket or camshaft seal. In these cases, the red color is the result of water or engine oil contamination.

My brake fluid is changing color: why and how should I change it?  

When brake fluid changes color, it can be a sign that the fluid is contaminated or that contaminants have accumulated in the brake system. Here's what to do if your brake fluid changes color:

  • Check the brake fluid level: Make sure the brake fluid level is adequate and between the "minimum" and "maximum" marks on the reservoir.
  • Identify the color of the brake fluid: If the brake fluid is brown, it may indicate that the fluid is beginning to deteriorate. If the brake fluid is yellow, it may indicate that moisture has accumulated in the brake system. Green brake fluid may indicate coolant contamination.
  • Have the brake system checked:If the brake fluid has changed color, it's important to have the brake system checked by a qualified professional. They will be able to determine the cause of the contamination and whether repairs are necessary.
  • Replace the brake fluid: If the brake fluid has changed color due to contamination or deterioration, it's important to have it replaced.


The color of new brake fluid does not indicate its quality! If brake fluid becomes very dark or muddy after use, it may be a sign that it is contaminated and needs to be replaced.

Brake fluid absorbs moisture from the air and, if not replaced regularly, can become waterlogged, leading to corrosion of internal brake system components and loss of brake performance. This corrosion can also cause particles to form in the brake fluid, causing it to appear dark or muddy.

However, brake fluid can become contaminated even if it retains its original color, so it's important to regularly check its dry boiling point or follow the manufacturer's recommendations for regular brake fluid replacement.

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