Who is using a low-viscosity brake fluid?

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The Critic

The Critic

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I am at 35,000 miles on the Prius and am ready to do a brake fluid flush with Techstream. There are various posts throughout the web of people using the low-viscosity DOT 4 fluids, such as ATE SL.6 and Pentosin DOT 4 LV, in place of traditional brake fluids in applications where low-viscosity fluids are not mandatory. Some of the benefits reported include smoother ABS cycling and different cold temperature brake feel.

However, the Prius braking system sees very little thermal cycling and use, so high-temperature performance is not the most important concern. Also, regenerative braking is always used to some degree, so I am curious how this would change with a low-viscosity fluid.

The low-viscosity fluid will cost $15-$20/qt, but the price is not a concern. What I am curious about though, is what differences have you folks noticed with a low-viscosity brake fluid in traditional brake applications.

Thanks.
 
I just have to ask.. Does Toyota call for a brake fluid change that early? I'm at about that mileage on my Civic and am unaware of a needed fluid change any time soon. Just curious.
 
I'm using Ate SL.6 in my Golf - just put it in at biennial brake fluid flush this spring. I haven't noticed any difference in performance, but I rarely activate ABS or traction control. Winter will be a better test of its effectiveness.
 
SLCraig, Honda recommends every 3 years, IIRC. Not aware of any mileage limits.

If I were changing fluids often and high temperatures were not an issue, I'd go with DOT 3 to allow for more moisture to be absorbed. Just my thoughts. I'd like to hear if someone has other suggestions on that.
 
Originally Posted By: benjamming
What are the mfg spouted benefits supposed to be? Why would I care about the viscosity of brake fluid since circulation is minimal?


Mostly for ABS systems. They have to respond and actuate rapidly. There are very fine passages and valving in them.
Some sytems do better with the thinner fluid.
 
Originally Posted By: mechtech2
Originally Posted By: benjamming
What are the mfg spouted benefits supposed to be? Why would I care about the viscosity of brake fluid since circulation is minimal?


Mostly for ABS systems. They have to respond and actuate rapidly. There are very fine passages and valving in them.
Some sytems do better with the thinner fluid.


+1
 
Originally Posted By: bigmike
SLCraig, Honda recommends every 3 years, IIRC. Not aware of any mileage limits.

If I were changing fluids often and high temperatures were not an issue, I'd go with DOT 3 to allow for more moisture to be absorbed. Just my thoughts. I'd like to hear if someone has other suggestions on that.


Regardless of the amount of moisture absorbed, the wet boiling point will always be higher with a DOT4.
 
I really don't see the benefit of a higher boiling point brake fluid in a Prius. Most of the time you are going to be using regenerative braking anyways. Even driving Highway 17, you would not approach the boiling point of DOT3 brake fluid.

On the ABS issue, I don't know. Out of all the years I've driven 17 or Hecker Pass I can only think of one instance of using my ABS and it worked just fine on DOT3.

As long as the fluid is fresh and clean, I'm not sure you would notice the difference. It definitely won't hurt anything.
 
Last edited:
Originally Posted By: Sunnyinhollister
On the ABS issue, I don't know. Out of all the years I've driven 17 or Hecker Pass I can only think of one instance of using my ABS and it worked just fine on DOT3.


Agreed. ABS has been around a long time, and it regularly gets exercised up here in the winter. I've only dealt with one vehicle that used DOT 4, and that was the Audi. Everything else with ABS called for normal DOT 3 brake fluid, and that includes my G.

I know that Prestone markets around three types of DOT 3 - a Ford DOT 3, an ABS DOT 3, and a normal DOT 3. They're all priced the same - go figure.
 
I use Pentosin DOT4LV in my car and my mom's car which both have ABS. Neither of us have needed to use the ABS, so neither of us could comment on how much better it works.

Pentosin DOT4LV can be found at all the Carquest central distribution hubs and it costs about $15 per liter.

Anyway, Garak, I recommend replacing DOT3 with DOT4 every time. I have always found that the fluid stays cleaner for a longer period of time.
 
Originally Posted By: artificialist
Anyway, Garak, I recommend replacing DOT3 with DOT4 every time. I have always found that the fluid stays cleaner for a longer period of time.


I have no problem with that philosophy, either. The Audi took DOT 4, and I used it. I may upgrade the G. DOT 4 is a little harder to come by here, though, and is obviously a little more costly. To make matters worse, I gave away my DOT 4 with the Audi.
wink.gif
 
Hah - I gave away all my Audi fluids and parts with my Audi as well...

I never realized there was a viscosity difference between dot 3 and dot 4. I knew dot 5 was totally different and could not be used. I use Valvoline 'synthetic DOT 3/DOT 4 ABS brake fluid' in my infinities and the bike. I don't remember noticing any difference in pedal or ABS feel after the swap.
 
Last edited:
Originally Posted By: CBR.worm
Hah - I gave away all my Audi fluids and parts with my Audi as well...


Yep, a bunch of filters, a jug of Pentosin, DOT 4, Bentley manuals, steering pump reseal kit, and the better part of a pail of 15w-40. Beck Arnley claims Pentosin is okay for Infiniti power steering, but I'm not using $30 a litre fluid when $25 per five litres of Dexron VI definitely meets the specification.

As for DOT 3 versus DOT 4 viscosity, I don't know if there is a difference or not either, or if it's a brand issue, or what.
 
I just noticed that the SL.6 is rated for 2 yr, while the Type 200 and Super Blue are rated for 3 years.

Hopefully the higher viscosity of the Type200 will not be an issue, as the longer service life is a good thing.
 
Originally Posted By: The Critic
Hopefully the higher viscosity of the Type200 will not be an issue, as the longer service life is a good thing.


I noticed that, too. I think worrying about brake fluid viscosity might be a bit much, though. Perhaps I'll go and see if Prestone lists viscosity for any of its three types of DOT 3 and its DOT 4.
 
I've been using the low vis ATE SL.6 fluid for about 3 years, and have not noticed a difference in performance compared to a standard vis fluid. Have not had any problems with it, and will continue to use it. It is claimed that low vis brake fluids are easier at bleeding out the air bubbles.
 
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