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Mineral oil is much less toxic than DOT, does not absorb water, has higher boiling point.

Bleeding Shimano brakes is almost as easy as unscrewing the caliper bolt and pouring oil into the lever system. On the other hand, for Avid-s one needs to observe strict vacuum.

Why would so many companies bother with an American-specific oil and vacuum-reliant system?

Mineral Oil
Shimano
Magura
Tektro
Gatorbrake

DOT
Hayes
Avid
Formula
Hope

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3  
DOT fluids have a higher boiling point, has a crisper bite and is supposed to be less reactive with rubber. However it's more corrosive to metal. Essentially it's an American standard but a universally availed and specified fluid. –  DWGKNZ May 23 at 11:15
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DOT brake fluid is what's used in auto and motorcycle brakes, and hence in more familiar and more consistent with existing manufacturing techniques. Additionally (and the reason for its use in autos), it's not damaging to rubber/plastic components as mineral oil will tend to be. –  Daniel R Hicks May 23 at 11:17
    
Strict vacuum? what? Are you referring to negative-pressure bleeding as opposed to positive-pressure caliper->lever bleeding? –  moshbear May 24 at 2:13
    
Also, DOT is generally standardized in terms of minimum performance. Mineral oil is a proprietary birds-nest of various chemicals. –  moshbear May 24 at 2:14
    
DOT is also widely available at auto parts stores significantly cheaper than specific bicycle brake fluid. I'm guessing there's also some advantages at design time to using well understood, standardised performance parts. –  Byron Ross May 27 at 22:14

1 Answer 1

Advantages of DOT over Mineral Oil:

  • DOT has a standard - product that meets the minimum standards is readily available at low cost
  • Compatibility with cheap materials used for seals
  • Hygroscopic, so water will not collect in a single part of the system

Disadvantages of DOT over Mineral Oil:

  • Corrosive despite inhibiting additives, damages paint, skin, metals etc.
  • Hygroscopic, so water is absorbed and the boiling point drops over time. Limited shelf life and operating life.
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Stop, collaborate and listen, here's a wiki to answer your question. –  Emyr Aug 1 at 11:50

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