Brake Fluid

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Sep 9, 2022 | 03:32 PM

Jim Coscette

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Brake Fluid

True or false? All dot 3 brake fluid is "synthetic."

Can I use ANY DOT 3 brake fluid in a 40 year old car with DOT 3 already in it?

Sep 9, 2022 | 04:29 PM

4-vettes

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False
yes

Sep 9, 2022 | 07:32 PM

kodpkd

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From: Loveland

DOT-3 by definition is synthetic.

Sep 9, 2022 | 08:59 PM

C3 Stroker

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From: Youngstown Ohio

Dot 3 is synthetic, and compatible with Dot 4, which has a higher boiling point. Dot 5 is silicone based and does not mix with Dot 3 or 4.

Sep 9, 2022 | 09:21 PM

Bikespace

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From: Virginia

It's really easy.

DOT 3, DOT 4, and DOT 5.1 are glycol-based, regardless of being "synthetic", and all compatible, but with ascending boiling points.
DOT 5 is silicone, is incompatible with glycol-based fluid, and may be completely incompatible with some recently made brake components (YMMV).

It's the most obvious numbering scheme ever!