Brake fluid comparison thread.

Discussion in 'General Chat' started by Guapish_Fliver, Jan 13, 2017.

  1. Guapish_Fliver

    Guapish_Fliver New Member

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    #1 Guapish_Fliver, Jan 13, 2017
    Last edited: Jan 13, 2017
    Mmmk, I have been really getting nitty gritty comparing brake fluids and have a few questions. Is there a way to determine how hygroscopic a brake fluid is? Does a fluid with a closer wet and dry boiling point behave more stable? I'm thinking the racing fluids with an extremely high dry bp may be more hygroscopic and require changing more often? Do the low viscosity brake fluids have the same brake feel? Is there any reason to use low viscosity?

    I feel like the difference between the wet and dry boiling point holds some significance. I shall call this the "spread". I boil some brake fluids like crazy with the bike bike so I started making comparisons, and think that the larger the spread, the more quickly the performance deteriorates once boiled or contaminated. At least the drop in performance is more noticeable with the fluids I've used with a larger spread IMO. Correct me if I'm wrong.

    A lot of these fluids in here are more for bikes but I wanted to see what some of the auto/track guys think about these fluids. For the bike I'm running bel Ray currently but may switch to rbf 600 after comparing prices. I change brake fluid too much to buy $30 bottles of 660 all the time.

    For the mini I think typ 200 is a good balance of performance and value for the street. If I track the mini I may want to switch to motul 5.1 but I noticed it turns black quickly like its leeching color from the lines or something when used in other applications. The Prestone and Valvoline are the same price, the Prestone has a higher dry bp BUT, a much larger spread making me think the Valvoline would be a better choice if you go longer between changes?

    Ok the first part of each line is price divided by bottle size to get cost per ounce. Then I subtract the wet from dry boiling point, and the last number is the "spread". For the first one the wet bp is 617 degrees f, the dry is 400, and the difference is 217. Feel free to add to the list I've compiled so far.

    Motul rbf 660 ($27.99/17oz=$1.64 per oz) 617-400=217
    Motul Rbf 600 ($17.54/17oz=$1.03) 594-421=173
    Bel Ray racing ($14.35/12oz=$1.19) 580-410=170
    Maxima racing 600 ($13.49/12oz=$1.12) 600-410= 190
    Motul 5.1 ($9.99/17 oz=$.58) 522-365=157
    Motorex 5.1 ($11.75/8.5 oz=$1.38) dbp not released? Wbp 356

    Typ 200 ($14/33oz=$.42) 536-392=144
    Pentosin lv ($14/33oz=$.42) 509-338=171
    Valvoline dot 4 ($6/32oz=$.18) 446-311=135
    Prestone ($6/32oz =$.18) 510-311=199
     
  2. cristo

    cristo Well-Known Member

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    Since you mention low viscosity fluids, ATE makes a 700 viscosity DOT4 compared to the usual 1400 viscosity,
    that's supposed to be more responsive in modern ABS systems. I have no idea what difference this actually makes
    in practice*.

    ATE SL.6 ($12/33oz = .36/oz) 509-338 = 171

    * Einstein -
    In theory, theory and practice are the same. In practice, they are not.
     
  3. Metalman

    Metalman Well-Known Member
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  4. cct1

    cct1 Well-Known Member
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    Yes, the higher BP fluids are more hydroscopic and require more frequent changes. ATE is less so, and is fine for a street car. Motul 600/660 is awesome--it's what I use on the track--buts it's overkill for the street, it's expensive, and needs to be changed every few months.

    You do not want to use a 5.1, motul or any other. It's silicone based, a no-no in our cars.
     
  5. Dave.0

    Dave.0 Helix & RMW Powered
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    In run Motul Rbf 600 and change it twice year once is the fall and before the Dragon.
     
  6. cct1

    cct1 Well-Known Member
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    That's about right. I bleed so much I'm constantly turning the fluid over.



    ATE you can easily go a year. Don't like it on the track though.
     
  7. Guapish_Fliver

    Guapish_Fliver New Member

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    No, all the 5.1 fluids are non silicone based and can be mixed with anything.

    Your thinking dot 5 which is silicone based, but they color it purple so it can be easily identified...
     
  8. Guapish_Fliver

    Guapish_Fliver New Member

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    #8 Guapish_Fliver, Jan 14, 2017
    Last edited: Jan 14, 2017
    Do you think it's the high dry boiling point that makes it more hygroscopic, or the size of the difference between wet and dry boiling point?

    Look what happened to this motul 5.1 after about 10-15 hours use :eek6:
     

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  9. cct1

    cct1 Well-Known Member
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    #9 cct1, Jan 14, 2017
    Last edited: Jan 14, 2017
    "DOT 5 is silicone-based brake fluid and is used in most new cars today. DOT 5 is expensive, but it has a dry boiling point of 356 degrees. Newer brake rotors tend to be smaller and thinner, which means they disperse heat a lot less efficiently. Also, DOT 5 does not absorb any moisture. DOT 5 will not harm painted surfaces and acts as a weather barrier for your brake system, preventing rust. DOT 5 can be used as an upgrade or replacement for both DOT 3 and 4, but should not be mixed with any of the other fluids. The procedures to convert your DOT 3 or 4 systems to the silicone-based DOT 5 are similar to the Dot 4 conversion procedure mentioned above. Silicone-based brake systems tend to be more difficult to bleed, but once this is accomplished, a DOT 5-filled system will resist rust better and last longer than the other formulations. Silicone brake fluid is also much lighter in cold temperatures, only about 900 weight at -40 F.

    A new formulation has recently been developed called DOT 5.1. This fluid is identical to DOT 5 silicone in both boiling point and viscosity; however, it is compatible in the poly-glycol based systems and anti-lock brakes as well. DOT 5.1 can be used in place of either of the poly-glycol-based fluids even though it has half the viscosity of DOT 3 or DOT 4 fluid. In fact, DOT 5.1 can be intermixed with the other non-silicone based fluids."

    Copied and pasted. The 5.1 actually looks ok.
     
  10. cct1

    cct1 Well-Known Member
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    #10 cct1, Jan 14, 2017
    Last edited: Jan 14, 2017
    The amount of water pickup is dependent on the glycol content. They are obviously adding other things in along with glycol to influence wet/dry boiling points, but at the end of the day it depends on the glycol.
     

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