no all brake fluids were created equal?

OK, I know that you can't mix dot 3 and dot 5. From what I recall one of the reasons for that was that dot 5 is synthetic and when mixed things go bad. But what about dot 3 synthetic? Reason I am asking is that I always used dot 3 prestone non synthetic and now all I can find is dot 3 prestone synthetic. If I add it what will happen? Can I mix them?

DOT 5 is silicon. Here's a couple of links. The first is a simple explanation of 3, 4 & 5. The second is a link showing a DOT 3 & 4 compatable synthetic.
http://www.shotimes.com/SHO3brakefluid.html
http://www.valvoline.com/pages/products/product_detail.asp?product=51

JoBo.

DOT 3 & 4 can be mixed... DOT 5 is NOT TO BE mixed with 3 & 4... DOT 5.1 can be mixed with 3 & 4... Clear as mud??

You should be fine to mix your 'synthetic' with the fluid you already have in the system...

-Will

willyb said:

DOT 3 & 4 can be mixed... DOT 5 is NOT TO BE mixed with 3 & 4... DOT 5.1 can be mixed with 3 & 4... Clear as mud??

You should be fine to mix your 'synthetic' with the fluid you already have in the system...

-Will

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That makes sense. What caused my confusion was the fact that dot 5 is silicone not synthetic as I originally thought.
Thanks y'all

One thing I did was buy one of those power bleeders. It's essentially a presurized jar that you pour brake fluid into and let it pressurize the system to 15-20psi. Then I go to all 4 wheels and with a hose on the bleeder, open them until clear fluid comes out. Once the clear fluid is coming out, close the bleeder and go to the next wheel. This way I know that the old stuff is gone.

Mark

markw said:

One thing I did was buy one of those power bleeders.
Mark

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Which one did you buy?
Are you happy with the way it performs?

Kejtar said:

OK, I know that you can't mix dot 3 and dot 5. From what I recall one of the reasons for that was that dot 5 is synthetic and when mixed things go bad.

Click to expand...

As noted, DOT 5 is silicone. Actually, except in ABS systems you can use DOT 3 or 4 with DOT 5 silicone. But when you do so, you lose the benefits of the silicone. The two types of fluid are not "miscible" (I think that's the term). They will co-exist in the system without any problems, but they don't mix together. It's like putting oil and water in a jar.

Once you add DOT 3 or 4 to a system using silicone brake fluid, the system reverts to the properties of the lowest rated fluid in it. The DOT 3 has a lower boiling point and will absorb moisture from the atmosphere, and if any portion of the fluid boils, you lose the brakes.

I have not been able to find out WHY you can't use silicone in an ABS system. Everyone seems to know this, but I've talked to engineers at Dupont, Chrysler, and a couple of other places and each person had a different reason. Normally in a situation like that I'd be tempted to try it just to find out the truth, but driving around without brakes isn't my idea of fun, so in this case I just go along with the advice and accept that I'll probably never really know why.

Eagle said:

I have not been able to find out WHY you can't use silicone in an ABS system. Everyone seems to know this, but I've talked to engineers at Dupont, Chrysler, and a couple of other places and each person had a different reason. Normally in a situation like that I'd be tempted to try it just to find out the truth, but driving around without brakes isn't my idea of fun, so in this case I just go along with the advice and accept that I'll probably never really know why.

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I may be wrong but I think I read that DOT 5 is very easily aerated. It traps small air bubbles easily resulting in poor braking performance. DOT 5 should not be agitated in any way. Since ABS systems have mechanical actuators and pulsating pumps, the fluid can become aerated.

falcon556 said:

Which one did you buy?
Are you happy with the way it performs?

Click to expand...

X-2

bajacalal said:

I may be wrong but I think I read that DOT 5 is very easily aerated. It traps small air bubbles easily resulting in poor braking performance. DOT 5 should not be agitated in any way. Since ABS systems have mechanical actuators and pulsating pumps, the fluid can become aerated.

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Add one more.

Of all the various reasons I've been given, this was NOT one of them. However, since I find it hard to accept that the rubber used in ABS systems is any less tolerant of silicone than the rubber used in conventional brake systems, and I have observed that silicone brake fluid IS easily aerated ... this makes a lot more sense than any of the reasons (guesses) the engineers gave me.

Thank you.

falcon556 said:

Which one did you buy?
Are you happy with the way it performs?

X2

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where can you find these power bleeders?