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DOT 5.1 Brake fluid

Discussion in 'Maintenance & Upkeep' started by Pikey, Mar 24, 2014.

  1. Pikey

    Pikey Active Member Staff Member 2 Years ROTM Winner 1000 Posts

    has anyone switched their brake fluid to DOT 5.1. I understand that DOT 5 can not be mixed with DOT 3 or 4, but DOT 5.1 can be. I am doing a fluid flush on my truck and wondered if anyone has used the newest stuff. it is supposed to not attract moister like the DOT 3 and 4 fluids do. Opinions?
  2. Jamm3r

    Jamm3r Member 1 Year 100 Posts

    Used DOT 5 in a 1949 Diamond T pickup I restored once. It worked out OK, but we were replacing all components in the brake system anyway so there was no concern of cross contamination.

    Plenty of people hate it but it worked out OK for us. On the other hand, I find that DOT3/4 work out fine for me too
  3. Pikey

    Pikey Active Member Staff Member 2 Years ROTM Winner 1000 Posts

    I am thinking that I will just go with a dot 3/4 synthetic.
  4. tbplus10

    tbplus10 Epic Member Staff Member 5+ Years 5000 Posts Platinum Contributor

    I used DOT 5.1 on a 70 Impala a few weeks ago after being recomended by the Tech guys at Prestone.
    The car was a light restore that I was trying to flip without spending a fortune on getting it road worthy.
    The brake system looked and worked good but my concern was the hydraulics probably hadnt had any maintenance in the life time of the car.
    I flushed it with DOT 5.1 then serviced it up.
    I put 1500 miles on the car before selling it and found no issues, as expected the the brakes were much more responsive after the flush.
    I know the new owner so I certainly keep up on any future issues that may come up with the brakes.
  5. thzpcs

    thzpcs Member

    Anyone know the tech specs between DOT3/4 and 5?
  6. Pikey

    Pikey Active Member Staff Member 2 Years ROTM Winner 1000 Posts

    [TABLE="class: spec4"]
    [TR="class: bg"]
    [TD]fluid

    DOT 3
    [/TD]
    [TD]

    Glycol
    [/TD]
    [TD]Boiling point
    dry
    over 205℃
    [/TD]
    [TD]Boiling point
    wet
    over 140℃
    [/TD]
    [TD]Viscosity
    100 C
    over 1.5cst
    [/TD]
    [TD]Viscosity
    -40C
    under 1500cst
    [/TD]
    [TD] PH

    7.0-11.5
    [/TD]
    [/TR]
    [TR]
    [TD]DOT 4
    [/TD]
    [TD]Glycol[/TD]
    [TD]over 230℃
    [/TD]
    [TD]over 155℃[/TD]
    [TD]over1.5cst
    [/TD]
    [TD]under 1800cst[/TD]
    [TD] 7.0-11.5
    [/TD]
    [/TR]
    [TR="class: bg"]
    [TD]DOT 5.1[/TD]
    [TD] Glycol
    [/TD]
    [TD]over 260℃[/TD]
    [TD]over 180℃[/TD]
    [TD]over 1.5cst
    [/TD]
    [TD]under 900cst[/TD]
    [TD] 7.0-11.5
    [/TD]
    [/TR]
    [TR]
    [TD]DOT 5
    [/TD]
    [TD]Silicon[/TD]
    [TD]over 260℃[/TD]
    [TD]over 180℃
    [/TD]
    [TD]over 1.5cst[/TD]
    [TD]under 900cst[/TD]
    [TD] 7.0-11.5
    [/TD]
    [/TR]
    [/TABLE]


    This is what I could find quickly. It is in degrees Celsius so to convert to Fahrenheit you need to multiply by 1.8 and add 32. So, 155C= (155x1.8)+32= 311F. I have seen different companies list different boiling points.

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