[N_Jay]

Does anyone have any experience that disagrees with the following.

Decent brand name brake fluid is about the same (as long as we are not talking about racing).

Pentorin, ATE, Brembo, Motul

Looking at DOT4LV as all the cars are ABS.

Any reason not to buy a 5 liter jug? It might not all get used up in 2 years, but most will.

[fpena944]

Does anyone have any experience that disagrees with the following.

Decent brand name brake fluid is about the same (as long as we are not talking about racing).

Pentorin, ATE, Brembo, Motul

Looking at DOT4LV as all the cars are ABS.

Any reason not to buy a 5 liter jug? It might not all get used up in 2 years, but most will.

Was going to jump in and disagree but then saw that you mentioned for racing use the same doesn't apply so yes, I'd say any reputable brand for street use should do the job.

My concern with buying the big jug is that with our humid environment it's possible the fluid could absorb water while stored that long. But I'm not sure how much of an issue that would be in a standard plastic container. Anyone done research on that?

[N_Jay]

Thought was that 2 years is the shortest "Change" schedule for cars is 2 years, and most people (not enthusiasts) probably change at 4 to 6 years, I figured for every day use adding 2 years in the container would have minimum down side.

Besides, if a few friends stop by to get brakes changed, it might not even make a year.

[i am not a traitor]

Is the recommended intervals for replacing brake fluid overkill? I ask because I have never replaced the fluid in any car that I've ever owned. The only exception is when calipers were replaced in my jetta years ago. Am I just getting lucky? Did the calipers fail because of the fluid or are the intervals on the side of the auto repair facility's?

[N_Jay]

Is the recommended intervals for replacing brake fluid overkill? I ask because I have never replaced the fluid in any car that I've ever owned. The only exception is when calipers were replaced in my jetta years ago. Am I just getting lucky? Did the calipers fail because of the fluid or are the intervals on the side of the auto repair facility's?

It certainly seems to be overkill.

In realty, I do a big bleed (almost a change per corner) when I change pads.
Since this tends to be 2 to 3 years, I assume I am getting a nearly full change every 2 pad changes.

The only cars I have had caliper failures on in the last 25 or 30 years were my Hondas that 1) went really long on a set of pads and 2) did not get as complete a change (Due to it being a Honda and before I got my Motive bleeder)

[worf]

1) Flushing brake fluid every two years is *NOT* overkill for a car you want to keep.

If you intend to keep a car for 10+ years, either change the fluid every two years (or at least three) or buy spares for calipers, hydraulic cylinders, ABS pumps, etc, If you want to not change fluid and keep it for 20+ years, buy spares for all the metal hydraulic lines and junctions.

Doubt me if you want. I have 20+ years now fixing/restoring 928s; that guidance is from that experience.

2) Stability of brake fluid is not guaranteed after the hermetically sealed can is opened to air. Use it within a few weeks or toss it.

3) Yes, any “good” fluid will do as long as the specs are appropriate. Personally, I use Pentosin Super DOT 4 in “Classic Porsches”(*) and Pentosin Super DOT 4LV in the 2015+ Porsches.

(*) I don’t know the year of the “cut line” between the LV and non-LV as I don’t work on ‘96-‘14.

[N_Jay]

I do LV for anything with ABS, especially modern ABS/Stability control systems. Originally I stuck with ATE SL.6, but now all the major brands seem to have an LV fluid. (Hence asking the brain trust)
For non-race cars I really wonder if there is that much difference between 2 and 4 years.
As you implied 2 to 3 years seems to keep the fluid 'at spec', so what the hell happens in a month or two in an opened and resealed can that does not happen in the car's brake reservoir?

Gave up on the 5 liter container because with shipping it was not as good a deal, and I could not think of enough to buy to get free shipping.

One Ebay seller has a great deal two 5-liter Brembeo DOT4LV for $75, but I would have had to find someone to buy one off me.

[David993S]

As others have said, brake fluid is hydroscopic so a 5-liter jug of it will absorb water if you keep it for two years. If you're talking about flushing your system every other year, just buy enough brake fluid at that time to do the job. And again, as other have said, flushing your system every two years is recommended. I've been using Motul in the Ferrari and 996 track car, and it's been fine. Unless you're racing or DE-ing, most any quality brand is OK.

Here's the reason you should change/flush your brake system every other year. I'm a little embarrassed to admit this, but here goes: I have rarely driven my 993S the past several years just because I have other cars plus I was tracking the 996 and paying attention to it. I had the 993 serviced a couple of weeks ago, including a brake flush. The tech had some little device that measured water content in the brake fluid. After just a few years, the water content was approximately 35-40%. I was astounded.

Change you brake fluid every other year regardless of how many miles you've driven.

[N_Jay]

I wonder what the scale is.
It can not be "by volume" or "by weight".

A big difference between the bottle on the shelf and the fluid in the car is the sealed cap.

Edit: looks like it absorbs 1% to 2% per year, with a recommend limit of 4%.

Guessing your mechanic misunderstood the reading his tester gave him. (3.5 to 4.0 not 35 to 40)

Also found out that DOT4 absorbs water faster than DOT3. (Maybe why we got away without changing fluid years ago?)

Interesting other fact, seems brake fluid is inherently stable, so an old sealed bottle is as good as new.

The reason I was looking at the big bottle is since I do 1/2 flushes, and don't really like mixing brands of fluids, since even 'compatable' fluids may have different composition.
Seems what I buy one year is never at a decent price next year.

I always found ATE SL.6 at a good price, but the last few years it was up and Brembo DOT4LV was at a good price.
Now Brembo is only a bargain in the 5 Liter size. So I guess I am back to ATE.

[i am not a traitor]

Thanks for the information. I'll definitely add this maintenance to my list of things to do. Just replaced the pads/rotors on the audi which would have been a good time to do it.

[Geza-aka-Zombo]

A lot of good information here. One clarification, brake fluid is hygroscopic.

[worf]

A lot of good information here. One clarification, brake fluid is hygroscopic.

[fast_freddy]

I flush/change brake fluid every two years almost irrespective of the usage. Tranny fluid every three-ish years and a coolant flush in concert with it. I also do ABC suspension/steering fluid flushes every two years. It costs a $30~ to do a complete brake flush so who cares (suspension/steering a bit more)? If you're fretting over the deminimis cost of a batch of DOT 5 fluid, perhaps a Benz/Porsche/etc., isn't the right car for your "budget"? Also, while doing the flush, it gives one the opportunity to see if there are leeks and such that need to be addressed. If your brakes fail, you might not have a good remainder of your life.

[worf]

… while doing the flush, it gives one the opportunity to see if there are leeks and such that need to be addressed.

This -^.

[Scott at Team Harco]

Leek soup is delicious. Yum.

[Geza-aka-Zombo]

DOT 5 was mentioned, which is not compatible with most modern brake systems. There is a DOT 5.1, which is something different. I'd recommend using what the owners manual specifies, probably DOT 4.

[worf]

DOT 5 was mentioned, which is not compatible with most modern brake systems. There is a DOT 5.1, which is something different. I'd recommend using what the owners manual specifies, probably DOT 4.

I assumed it was a brain fart. But, yes, indeed, Porsche calls for DOT 4.

[SeanR]

Agree with everything Worf said.

Having said that, in my own cars I used to neglect that and found out the hard way that it needs to be done. The day I had Matt Farrah in my 928 on the track, on 6 year old brake fluid (knowing I needed to change it before it went on track) the brakes lasted about 2 laps before the fade happened. I'm a fan of ATE and used to swap blue for gold every few years. Since we can't get blue anymore one can actually see how brake fluid looks after a couple years in the system between changes.

[linderpat]

I use hi-temp Pentosin, for regular track use, then keep it in for street use until the next flush. Really good stuff. ATE is excellent too, for both street and track.