old guys rule
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Can you mix dot 4 brake fluid with Dot 3 synthetic brake fluid?
Brake fluid mix
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Yes. I believe the only no go is dot 5 with others, however 5.1 supposedly OK.
I believe Rick Erenberg (Mopar Action) stated that DOT 5 would work with 3 and 4 as adding, even inadvertently, to a system could cause a braking failure that the DOT would not allow if an adverse reaction could occur due to chemistry. Anyone else read that statement by Rick?
Mike
Mike
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Not sure about any Erehnberg specific quotes on it.
Glycol and silicone-based fluids are NOT compatible. It is important not to mix these fluids. Only use DOT 5 in a completely dry system or in a vehicle that already has DOT 5 in the system. DOT 3, DOT 4, and DOT 5.1 are all interchangeable.
DOT 5
DOT 5 brake fluid is a silicone-based fluid. Silicone-based fluid is hydrophobic, meaning it repels water. Moisture introduced into a brake system with DOT 5 fluid does not mix with the brake fluid. This causes the moisture to freeze or boil and can lead to brake fade.Glycol and silicone-based fluids are NOT compatible. It is important not to mix these fluids. Only use DOT 5 in a completely dry system or in a vehicle that already has DOT 5 in the system. DOT 3, DOT 4, and DOT 5.1 are all interchangeable.
old guys rule
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Thanks guys
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I've read that statement by Rick, and he was incorrect. He stated that DOT 3,4 and 5 refer to boiling points only, and not whether or not they had silicon in them. He even said that some DOT 3 has silicon, which contradicts what the DOT requirements are for brake fluid. I like a lot of Rick's writings, but don't agree on this one.
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