In a message dated 6/1/03 6:50:44 PM Eastern Daylight Time,
racecase@oneimage.com writes:
> I've always used Castrol brake fluid because
> petroleum-based fluids were said to eat away the rubber seals.
>
> I went to 3 auto parts stores and none carry Castrol anymore. They now have
> various brands of synthetic brake fluids. Will those be okay or damage my
> seals?
>
Without going into chemistry and engineering, I don't think DOT 3 or DOT 4
are petroleum-based fluids. They are alcohol/glycol mixtures which absorb water
(hydroscopic).
We who grew up with British cars were trained to use Castrol. I remember it
was called Girling Crimson before Castrol LMA. The story was that regular
"American" brake fluid would destroy the rubber seals.
Somewhere along the way they became DOT 3 & DOT 4.
When Silicone Brake fluid came along for civilian use it was tagged DOT 5.
Silicone has been used by the military for a very long time.
Silicone will not absorb or mix with water.
Now there is Synthetic brake fluid. Valvoline has "Syntec" which is
advertised as meeting DOT 3 and DOT 4 specifications. I would think that it is
still
alcohol based and hydroscopic. It is NOT Silicone.
I have used Silicone for many years and this includes a lot of race cars. I
have been satisfied with the performance and low maintenance. However, nothing
beats a high boiling point DOT 3 such as AP550, 650, etc. in very severe
racing applications, but the maintenance of the system is higher as can be
expected.
So....don't confuse Silicone with Synthetic although I think Silicone is a
synthetic.
I have just started using the Valvoline Syntec in street applications and am
confident it is completely interchangeable with Castrol DOT 4 and you don't
need to rebuild the system. A good flushing is a smart idea, but mainly just to
purge out any old water saturated fluid.
Jack Woehrle
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