Synthetic Break Fluid Question

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dcardarelli Contact options for registered users 's Avatar posted on
March 9, 2012, 2:01 pm
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I have a 2008 Buick Enclave, and about two months ago I needed to add
some break fluid.  I added about 4 ounces DOT 3 synthetic fluid. I
found out that if the original fluid was not synthetic, it is not a
good idea to mix them.

The owner's manual specifies only DOT 3 with no mention of synthetic
or not (probably because synthetic may not have been around at that
time).

The question is, should I have the break fluid changed out (if the
original oil is non-synthetic) or is it OK just the way it is?

Thanks,

Dave


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PeterD Contact options for registered users 's Avatar posted on
March 9, 2012, 2:18 pm
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Re: Synthetic Break Fluid Question

On 3/9/2012 2:01 PM, dcardarelli@comcast.net wrote:

First I'm going to guess you mean brake, not break, right?

And where did you 'find out' it was not a good idea to mix synthetic
DOT-3 and regular DOT-3 fluid?


--
I'm never going to grow up.

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dcardarelli Contact options for registered users 's Avatar posted on
March 9, 2012, 4:24 pm
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Re: Synthetic Break Fluid Question


Oops, yes, brake fluid.  I went to NAPA today to get another can, and
I then noticed on the shelf below was non-synthetic fluid, DOT 3.  I
asked the counter guy the difference between the oils.  He commented
that mixing should be avoided as it can cause clouding.  He thought
because the car is 5 years old, it probably was not synthetic.

The can I bought earlier (synthetic) says it satisfies all DOT 3
requirement and no cautions statements.  I took that as it being OK.

Meanwhile, I have an appointment to be sure I do not have a leak
somewhere.

I'd appreciate your thoughts.

Dave

 

PeterD Contact options for registered users 's Avatar posted on
March 9, 2012, 5:41 pm
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Re: Synthetic Break Fluid Question

On 3/9/2012 4:24 PM, dcardarelli@comcast.net wrote:

As long as both cans are marked DOT-3 (or DOT-3/4) there is no problem
mixing them. They are compatible. The problem arises when DOT-3/4 is
mixed with DOT-5 (silicone) fluid--these are not compatible.

The parts counter guy doesn't know what he's talking about.

All DOT-3/4 brake fluid is glycol based (same stuff as in anti-freeze)
and not oil based. That is why DOT-3/4 brake fluid is hygroscopic
(absorbs moisture). DOT-5 silicone brake fluid is very different, it is
oil based, and won't absorb moisture. But don't ever use DOT-5 in a
vehicle that is not designed for it!

--
I'm never going to grow up.

 

dcardarelli Contact options for registered users 's Avatar posted on
March 9, 2012, 6:50 pm
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Re: Synthetic Break Fluid Question


Thanks, Peter for clearing this up for me.  Yes, the fluid can, the
manual, and the reservoir cover all say DOT 3.

The young counter guy was polite and courteous but innocently had some
mis-information.

I have added a total of 4-5 ounces the past months, and as I
mentioned, I want to have it checked for possible pinhole leak. Other
cars I have owned in the past has normally not needed brake fluid
hardly at all.

Again, thanks for getting back to me on this.

Best regards,

Dave

 

PeterD Contact options for registered users 's Avatar posted on
March 10, 2012, 8:24 am
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Re: Synthetic Break Fluid Question

On 3/9/2012 6:50 PM, dcardarelli@comcast.net wrote:

I'd suggest a careful inspection of the brake system to ensure you don't
have an external leak. It is remotely possible the leak won't be visible
but that's rare. As you note, it is unusual to have to add fluid, though
as brake pads wear the level will drop some as the pistons move out more.

--
I'm never going to grow up.

 

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