Jim,

Silicone brake fluid (DOT 5) is of great value, in my opinion, 
for cars not driven very much, as too many people tend to view 
periodic maintenance as something done on a mileage interval, 
rather than time interval, basis.  I use it in three of my
vehicles, two Studebakers and one motorcycle, and don't use it 
in two others, another Studebaker and our Saturn.

DOT 5 has charhacteristics about it that must be understood and
dealt with, or you'll regret having installed it.

The most conservative view:

1.  ALL, and I mean ALL, old DOT 3 or 4 fluid must be removed from
your present brake system.  This means disassembling all parts, 
including master and slave cylinders, to thoroughly clean them of
old brake fluid with alcohol.  DOT 5 does not mix with any other
brake fluid.

2.  DOT 5 is composed of smaller molecules, meaning it leaks past
joints in brake line that DOT 3 or DOT 4 won't.  You find yourself
tightening everything, and replacing some junctions, in order to
keep the DOT 5 inside your system.

3.  While the rubber parts used in today's brakes does not react to
DOT 5, the same cannot be said of the rubber bits used in the systems
of older cars.  Some stuff as current as the 1980's will swell up
when exposed to DOT 5.  Check with others about your current car and,
if you switch to DOT 5, avoid NOS brake parts that the fluid will
come into contact with.  You'll find out soon enough if a part will
work with DOT 5 after installing it on your car.

4.  DOT 5 has a propensity to hold air in suspension within itself,
making it very difficult to bleed.  Never shake the can, always
pour it out VERY SLOWLY and expect to spend extra time bleeding your
brakes to expel all of the air in the lines.

Can't think of anything else.  Once you've switched, you can effectively 
kiss corrosion goodbye, as long as ALL of the old fluid is gone and you
never mix DOT 3 or 4 with the DOT 5.

Chris Altenburg

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