Are DOT 3 and DOT 4 Brake Fluid interchangable?

mad52 · Apr 3, 2023

I need to add brake fluid, and the manual says DO NOT MIX Dot 3 with Dot 4! But the service guys at Subaru says it's ok~!? Any insight on this? (they only carry Dot 3, but my receipt for recent fluid change says Dot 4)
thanks

dukey33 · Apr 3, 2023

3 and 4 are fully miscible. No concerns.
5 and 5.1 are not compatible with 3 or 4.

stevenva · Apr 3, 2023

Different boiling points 3/4

motoretro · Apr 3, 2023

I changed mine out and had complete flush done of system just to make sure there were no issues. Never had a issue afterwards.

Are DOT 3 and DOT 4 Brake Fluid interchangable?

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