[TR] Brake fluids again

Randall TR3driver at ca.rr.com
Wed Apr 15 23:55:40 MDT 2020


All brake fluid is "synthetic" whether it says so on the can or not.  It's
not made from petroleum distillate.

Yes, DOT 4 will absorb water, eat paint and so on.  Castrol claims theirs
absorbs slower than others (the "LMA"), but it still absorbs.

DOT 5 is a completely different chemistry, a silicone oil rather than the
glycols used in DOT 3, 4 and 5.1.  It does not absorb water, eat paint,
become corrosive over time, etc.  

Look for the word "silicone" on the label.  DOT 5 must have it, the others
cannot have it.

The word "synthetic" is totally meaningless for brake fluid.

FWIW, both of my Stags have DOT 5 in them.

-- Randall 

> I'm rebuild brakes and clutch with new seal on a Stag. I have 
>  this brake fluid 
> 
> https://www.bpnorthwest.com/fluid-brake-clutch-castrol-lma-12-
> oz.html  
> 
> which says DOT 4 synthetic  (Castrol) . If it is synthetic, 
> will it absorb water? 
> 
> I'm a bit confused as people are saying get DOT5. synthetic. 
> Is the buzz word synthetic? 



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