The properties of brake fluid make it a frequent topic of discussion,
and you know it makes me wonder just how much or little thought has
been put into its continued use.

Brake fluid absorbs water from the environment.  This water then
causes corrosion in the system, brake fade when the brakes get hot, it
might increase dissolved gases in the fluid.

I've never seen old brake fluid bled out that wasn't filthy.  Where's that from?

What is it about brake fluid that makes it indispensable to a braking
system?  Isn't just about a certain level of viscosity?  If that's so
can't something better be substituted for it?

That said, there is a wide variation in the wet/dry boiling points of
brake fluid.  Even within one DOT rating.  The vanagon uses dot 4, but
dot 5.1 can also be used and is compatible with dot 4, and has a wet
boiling pt. MINIMUM of 180C.

For some reason the high boiling point stuff, even though it's the
same chemistry as dot 4 in general, is much more expensive.  You're
better off being diligent about changing your brake fluid regularly.

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