I to be bleeding the brakes and ran the end of the Blue period 4 so ns finished up with dot 3. Are they compatible or have to I flush and also refill with just one?


You are watching: Can you mix dot3 and dot4 brake fluid

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The difference between the fluids is the temp rating. Girlfriend shouldn"t mix or use opened up container brake fluids (unless its known to be totally free of contaminates) that havn"t been stored properly. The blue dot 4 is a greater temp, violet is a synthetic grade 4, the dot 3 is not.Flush and fill with one or the other of at least the great the automobile requires .
Never heard of artificial DOT 4. I assumed all dot 4 were glycol based, very same as dot 3 and chemically, completely compatible through it.I can"t believe two not compatible fluids could carry the very same DOT specification. Or space you speak the purple and also blue dot 4"s room compatible? If so they room compatible through DOT 3.What is "synthetic" brake fluid. I thought it to be a Valvoline marketing gimmick uneven you are talking about DOT 5 silicone.
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DOT4 and DOT3 are both polyethylene glycol based, which is a synthetic polymer. There"s no such thing as a mineral based automotive brake fluid. It"d be likewise redundant to industry water together inorganic.DOT4 boosts the boiling point over DOT3 by including borate esters. That"s it. If the bulk of the fluid had performance characteristics sufficiently past the minimum forced by FMVSS, including a little amount the DOT3 is nothing to sweat about. Obviously the greatest boiling point feasible is preferable for safety reasons, but you"d have to be driving like a crazy human being to obtain into trouble.DOT4 is cheap to produce, so fluids through DOT3 maximum performance don"t make lot sense. Some manufacturers have resorted to simply packing DOT4 into bottles marked DOT3/DOT4 so the target market will no ask questions.What is important, however, and was stated before, is care in dealing with PEG based brake fluids (everything yet the silicone DOT5). Always use brand-new bottles, because the oil automatically starts taking in moisture, therefore the necessity to readjust it each year or 2 to maintain the boiling point.
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JoinedDec 8, 2008LocationAppleton, MaineTDI99.5, '01 A4 Jetta sedans, 5 sp box, Hamman mod, Joey mod, Bilsteins, 2.00" lift
Thank friend for the clear, concise response. Ns love hearing together answers based on real knowlege and not simply parroted everything from "the net."
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compu_85Gadget Guy
JoinedSep 29, 2003LocationSpringfield VATDI... Nobody :S
Oct 12, 2011


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I think some DOT3 fluids resist water much better than DOT4 fluids. ~ above a vehicle that hasn"t had actually its brake liquid flushed in a when I choose to begin out through DOT3, leave it in for a week, climate re-flush v DOT4 to gain all the crap out. -J