DOT 3, DOT 4 and DOT 5 brake fluid compatability? | FerrariChat
Buy

DOT 3, DOT 4 and DOT 5 brake fluid compatability?

Discussion in 'Technical Q&A' started by Ekasilicon, May 6, 2004.

This site may earn a commission from merchant affiliate links, including eBay, Amazon, Skimlinks, and others.

  1. Ekasilicon

    Ekasilicon Formula Junior

    Jan 21, 2003
    507
    #1 Ekasilicon, May 6, 2004
    Recently I was bleeding my brake lines in my M3 and ran out of DOT 4 fluid. I went to the auto parts store to pick some up and they had DOT 3 and DOT 5 fluid, but no DOT 4. The man at the store said DOT 5 would be just fine. I wasn't sure if I believed him, so I went to another store and bought DOT 4.

    Since then I have wondered if DOT 5 can be a substitute for DOT 4. Does DOT 5 mix well with DOT 4, or are they two completely different fluids?
     
  2. Mule

    Mule F1 Rookie
    Owner Rossa Subscribed

    Jun 25, 2003
    3,758
    Alaska
    Full Name:
    Mule
    #2 Mule, May 6, 2004
    Before this gets into a shooting war on which is better. My understanding is that DOT 3 and DOT 4 are compatible, while DOT 5 is synthetic and does not mix with the others. Some bottles say DOT 3/4, but none say DOT 4/5 or DOT 3/5.

    The synthetic was developed for military vehicles and does not absorb water, so it is good for cars that may be "inactive".

    I was in the same situation, since Ferrari dealerships use "Tutela Extreme 5" brake fluid, but it is DOT 3/4, not DOT 5 despite the name, so I was confused, too. Good call on going to another store.
     
  3. Bryan

    Bryan Formula 3

    Nov 1, 2003
    1,310
    Montrose, Colorado
    #3 Bryan, May 6, 2004
  4. Mule

    Mule F1 Rookie
    Owner Rossa Subscribed

    Jun 25, 2003
    3,758
    Alaska
    Full Name:
    Mule
    #4 Mule, May 6, 2004
    Bryan is right about a lot of opinions. My correction is that DOT 5 is Silicone instead of sythetic.
     
  5. Schatten

    Schatten F1 World Champ
    Owner

    Apr 3, 2001
    11,238
    Austin, TX
    Full Name:
    Randy
    #5 Schatten, May 6, 2004
    correct, and NOT used for this purpose.
     
  6. Mitch Alsup

    Mitch Alsup F1 Veteran

    Nov 4, 2003
    9,741
    #6 Mitch Alsup, May 6, 2004
    Correct:

    Dot 3 and Dot 4 are Glycol
    Dot 5 is Silicone
    and just to make maters easy to remember
    Dot 5.1 is glycol again
     
  7. Ekasilicon

    Ekasilicon Formula Junior

    Jan 21, 2003
    507
    #7 Ekasilicon, May 6, 2004
    So could you use DOT 5.1 in DOT 4 systems?
     
  8. rsrx

    rsrx Karting

    Dec 11, 2003
    59
    Encinitas, CA
    Full Name:
    Alphonse
    #8 rsrx, May 6, 2004
    FWIW, and I dont want to get flamed, I've heard that Motul RBF is a DOT 5.1 fluid.

    I personally have used Motul RBF on my last car..a 5.0 Mustang with COBRA front brakes and Bear Racing rear discs and it worked awesome for me.

    Please...no flaming...just trying to help...;-)

    Alphonse
     
  9. Smiles

    Smiles F1 World Champ
    Lifetime Rossa Owner

    Nov 20, 2003
    16,675
    Pittsburgh, PA
    Full Name:
    Matt F
    #9 Smiles, May 6, 2004
    Yes. That's probably not ideal, but they are compatible.

    DOT 3, 4, and 5.1 are glycol based, as Mitch says. They are different in their boiling points and other properties.
     
  10. Mitch Alsup

    Mitch Alsup F1 Veteran

    Nov 4, 2003
    9,741
    #10 Mitch Alsup, May 6, 2004
    You should treat Dot 3, 4, and 5.1 as barely compatable. And you should treat old fluid and new fluid as basically incompatable. If you need to top up, consider just flushing the whole system (about $12 in fluid if you use a power bleeder).

    For typical use in a Ferrari, you should be flushing the system at least once a year (4 brakes and the clutch). For high performance driving 4 times a year, for track racing once a day to once a weekend.
     

Share This Page