Rick's Free Auto Repair Advice

Brake Fluid DOT 3

Brake Fluid DOT 3

Brake fluid DOT 3 and DOT 4 are made with glycol-ether and boil lowering additives and anti-corrosive additives. Glycol-ether is used because it has a high boiling point and is compatible with the rubber components used in an automotive braking system.

DOT 3 fluid is approximately 80% glycol ether base. The boiling point of DOT 3 brake fluid is rated at 401°F with no water in it and as low as 284°F if it’s holding water.

DOT 4 has a higher boiling point than DOT 3, making it seem it’s the better choice. However, DOT 4 absorbs moisture more readily (about 20% faster) than DOT 3. That’s why DOT 3 is preferred by many carmakers.

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Posted on by Rick Muscoplat


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