<VV> dot 3,5 - FMVSS 116

[Chris & Bill Strickland]

>You can't mix DOT 3 (glycol) fluid with DOT 5 silicone.
>
YES YOU CAN!  in terms of using them together in the same brake system 
-- the two fluid types, glycol & silicone, although compatibile, do not 
mix into a homogeneous mixture, which is one way to tell them apart (add 
a litle of the unknown fluid to some known fluid and  if they mix into 
one homogeneous solution they are the same.

to repeat myself from an earlier post, compatability is required by 
federal law -- 'Classroom Manual for Automotive Brake Systems', by Lane 
Eichhorn, Ken Layne (ISBN:0766809374) points out that although it is not 
reccomended, FMVSS 116 requires that types DOT3, DOT4, and DOT5 brake 
fluids be compatibile with each other in a system.  Note that this does 
not say they must blend into a homogeneous mixture if they are of 
different types. Same types *are* required to blend. 

MIL-PRF-46176B, dated10 January 2001, PERFORMANCE SPECIFICATION. BRAKE 
FLUID, SILICONE, AUTOMOTIVE, ALL-WEATHER, OPERATIONAL AND PRESERVATIVE, 
states that DOT5 "can" be mixed with DOT3 or DOT4, but not that it 
"should" be:

"6.5 Interchangeability. Brake fluid covered by this specification can 
be used in the same equipment and systems as the brake fluids covered by 
VV-B-680. However, all VV-B-680 [DOT3 or DOT4 fluids] or other 
non-silicone fluid should be removed and flushed from the brake system 
before using MIL-PRF-46176 fluid."

Can you envision -- "Sorry Sarge, I can't take my humvee into the 
batttle zone, it is low on brake fluid since I fixed the broken line, 
and it is one of those old glycol filled rigs and all we have is this 
new BFS (silicone) fluid and I can't mix them."