We've talked about brake fluid in other threads not too long ago, but I have since acquired the equipment to bleed my brakes via a vacuum method, 2nd best only to the superior but more expensive pressure method (equipment wise). My plan is not just to bleed air but to completely
replace all the fluid in all of the lines and cylinders for the whole system on four or five cars.

We also talked about the difference between Dot 3 and Dot 4 fluids, the main difference being a
higher boiling point for Dot 4. We also said that for most regular driving Dot 3 is fine, that Dot 4, though "better", is not really needed in most cases for regular driving. We also discussed that all non-Dot 5 brake fluids are naturally (chemically) hygroscopic, and 100% miscible in any proportion with zero loss of any desirable chemical, specific gravity, or physical properties regarding fluid dynamics etc. We also learned that the concentration and quality of additives was important because those antioxidant additives partly determine how long a given brake fluid will protect a brake system from deterioration, other things being equal.

But there is something that we didn't talk about that I since learned. And that is there are some
brands of Dot 3 that are better quality than other brands of Dot 4, even with the lower boiling point. I don't know the specific parameters that make one Dot 3 superior to another brand of Dot 4, but apparently there are racers that use certain superior brands of Dot 3 in lieu of Dot 4 because it is better quality, even though on paper Dot 4 has a higher BP.

So that got me thinking. In preparing for flush day, I will be looking for the best quality Dot 3 or Dot 4 fluids in their respective brands, and then choosing one based on my findings. I will naturally prefer Dot 4, but in reality I would do better with a best quality Dot 3 vs a lesser quality Dot 4, because I'm just driving my truck to work with occasional light to medium hauling with my stock F150.

So far in my research, with the possible exception of so-called advertised "racing" dot 3 and dot 4 brake fluids, how could I determine which "non racing" brake fluids, assuming that is a real thing, might be better or best quality fluids ? Is sticking with a major brand a safe enough assumption that I would be getting a fluid in the 80th percentile or better of quality for example, or do you think that going with major brands might not be enough to determine which Do3 or Dot4 fluids would be
better quality than other brake fluids ? BTW, some of those "racing" brake fluids seem to be way overpriced, and if they really deserve those prices, then that's probably the fluid I won't use because I'm not racing, I'm just and old fat white guy driving a F150 to work with occasional light to moderate hauling.

If it comes down to "just buy any major name brand of brake fluid" and call it a day, then that's fine. But if there ARE clear winners in terms of quality for either Dot3 or Dot 4, that
aren't ridicuously priced and labelled "racing" brake fluids, would you be so kind to share that
information ? I know lots of you guys have worked in related industries with chemical and materials engineering backgrounds, heavy industries and skilled trades, and professional auto and diesel mechanics experience as well.

Any and all advice would be appreciated in my preparation for flush day (no pun intended), or or flush week or flush month depending on work, weather, and my back. No I'm not crazy, this is one of my "hobbies" at home being a physically inactive IT and professional couch potato. I grew up working on cars and a few years ago I returned to my roots after failing miserably but delightfully at golf in earlier times.

So what can you guys advise specifically in the finest tradition of the mighty Sigform Brain Trust ? Not having worked in these fields I'm pretty helpless, so any and all advice would be greatly appreciated.

I’ve always used Walmart brand Dot4 and never had a problem. I have some cars that were originally dot3 and some cars that are dot 4. I’ve replaced all of the dot3 fluid with 4 since it’s backwards compatible.

And I always change it every 3 to 4 years regardless of mileage.

I would go with DOT 4 and call it a day. It has to meet a minimum standard to qualify.

As to using a performance brand they probably just buy in bulk and have their label put on the can. Doubtful they manufacture their own fluid.

Of course that is just my opinion but that is what I would do.

These are the two I have used and would use again. ATE and Motul.

Both are Dot 4. It's been a few years since I really looked at brake fluid so there may be something better but those were the go to.

Once you open a can it will start to absorb moisture so when you flush always use a new unopened can. I also normally get rid of a can year or so after opening it.

ATE used to make theirs in both blue and normal color. This was nice since you could easily tell when you had flushed each line out but the .gov decided blue fluid may confuse someone and put an end to it.

Stay away from DOT 5 as it's silicon-based and will damage systems not designed to use it.

If you have any small leaks where you connect the rubber fitting of the vacuum bleeder system to the bleeder on the caliber a little thick grease around the edges of the rubber will help. Just wipe it off when finished.

https://www.amazon.com/ATE-706...uality/dp/B003VXRPL0

https://www.amazon.com/Motul-M...thetic/dp/B004LEYJO4

We use NAPA Dot 4 in all of our police cars. Nary an issue.

Just change it every two to three years and you will be just fine.

More expensive does not mean better.

Castrol LMA.
Great fluid, easy to find.
Not expensive.

It makes no difference. The reason it's called "DOT 3" or "DOT 4" is because it's a specification; any of the brake fluids meeting that spec are acceptable. You may also mix brands of the same spec without issue. So long as it's not incompatible, it's just fine, and you won't gain advantage one brand over another.

I applaud you caring and maintaining your vehicle. But for your purposes "racing" fluid is over-thinking it.
I get DOT3, 4 and 5 from my auto parts store and as long as I see the foil seal under the cap I'm happy. Also, if you have a quart of fluid that's been opened and laying around your garage for more than 2 months pitch it. Use several of the smaller bottles as once the seal is broken you're at the mercy of humidity and foreign substances.

Im a little confused, is it youre trying to maintain all your vehicles to very high standards or are you suffering from some brake performance issues?

Im not trying to be smart. For example, if you said you lived in mountainous area, brake performance and longevity would be very different than here in southeast.

What is "racing" brake fluid? If this is silicone-based DOT5, no car maker recommends it. It is not compatible with, and may be outright harmful to, ABS systems. Just put DOT4 or even DOT3 in and you'll be fine.

quote:

What is "racing" brake fluid?

Brake fluid with a higher boiling point than the minimum for DOT 3 and DOT 4. It's commonly used by people doing track days or high performance driving schools. My uncle uses it in his 914/6 track car as well as his 911. He told me regular brake fluid will last about two sessions.

quote:

Originally posted by egregore:
What is "racing" brake fluid? If this is silicone-based DOT5, no car maker recommends it. It is not compatible with, and may be outright harmful to, ABS systems. Just put DOT4 or even DOT3 in and you'll be fine.

First, there is a simple test for whether you have DOT3 or 3, and if you have DOT5. Get a clear container and add water. Add a tablespoon or two of your brake fluid. Shake, then set it down and go do something else for an hour or two.
DOT3 and 4 will mix with water and stay mixed. DOT5 will separate from water and collect on top of it.
I've seen and use DOT5 in Harleys. I imagine other bikes may use it as it does have a high boiling point.

quote:

Brake fluid with a higher boiling point than the minimum for DOT 3 and DOT 4.

Conditions the OP's car, and those of 99% of the rest of us, will never see. But if it is still DOT 4, it won't cause any harm, except to his wallet.

quote:

Originally posted by Oldrider:

quote:

Originally posted by egregore:
What is "racing" brake fluid? If this is silicone-based DOT5, no car maker recommends it. It is not compatible with, and may be outright harmful to, ABS systems. Just put DOT4 or even DOT3 in and you'll be fine.

First, there is a simple test for whether you have DOT3 or 3, and if you have DOT5. Get a clear container and add water. Add a tablespoon or two of your brake fluid. Shake, then set it down and go do something else for an hour or two.
DOT3 and 4 will mix with water and stay mixed. DOT5 will separate from water and collect on top of it.
I've seen and use DOT5 in Harleys. I imagine other bikes may use it as it does have a high boiling point.

Dependent on year and model. Starting in '05 some models started specifying DOT 4, also the year ABS started appearing on baggers.

I’ve always used ATE Super Blue. I just looked for a link, and it appears it is no longer for sale in the US... because it was blue.

They have a replacement for it. I preferred it because I had much less if an issue with brake fade. It was also nice, being blue, because you knew when you had completely flushed out the old DOT 3 fluid.

http://www.ate-brakes.com/products/brake-fluids/

I use Motul 600 in my track car. There has never been an issue with fade due to fluid temp.

My brother was addicted to brake fluid, but he could stop anytime he wanted.

I loved ATE blue and ATE regular since you can use the two colors to make sure you got the system fully flushed. Unfortunately DOT killed that option at least in the supply chain I use. I still like ATE since it comes in metal cans which means shelf life is very long and the price is right. I have used it racing for many years and been totally happy. That said in my non race vehicles I use Castrol AP (formerly LMA) as it is simply the best option if you are not bleeding brakes on a regular basis.

If you are looking for the highest minimum boiling point only, you should also consider DOT 5.1, not to be confused with DOT 5. DOT 5.1 is a glycol based fluid as is DOT 3 and 4 and can be mixed. It is also pricier.