Michael, this topic always starts major controvercy.
The bottom line seems to be:
Both types of fluid work very, very well, especially in properly maintained
brake system in a street driven car.
Dot 3 or 4 is inexpensive, a bit easier to bleed, absorbs water, and
is a highly effective paint stripper.
Dot 5 is expensive, a little harder to bleed, does not absorb water, and is
harmless to paint.
In my TR4A, which has decent paint, I use silicone. Which is a good thing,
because occasionally a drop gets on the painted surfaces. It doesn't seem to be
that hard to bleed this simple brake system and the pedal is very firm -
especially since I installed braided stainless lines.
All my other vehicles use regular Castrol LMA Dot 4. Which also seems to work
great. I'm SUPER careful not to get any fluid on anything.
If you're the kind of guy who can pull a brake or clutch master cylinder
without getting any brake fluid on anything, you're a better man than me. I
salute you.
These fliuds DO NOT MIX. When mixed, even in tiny residual amounts left in a
drained brake system, they turn into an acidic, seal eating, metal corroding,
mess. If a system is going to be converted from DOT 4 to DOT 5 it really should
be totally cleaned out, every single inch of hose pipe and every singe
component.
I like the silicone, but with proper maintenence (yearly bleeding), Castrol
LMA DOT 4 works great. I would go the extra and use the Castrol LMA DOT 4, not
the el cheapo DOT 3.
Good luck!
Chris Lillja
Spit MKIV
Norton Commando
TR4A
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