DOT3 vs DOT4 Brake Fluid

[edyvw]

What's wrong with using LV on the track?

They get too thin. No track specific fluid is LV. There are LV fluids that have relatively high dry boiling point where theorethically they could be used on track. But, it is absolutely not recommended.
For example, ATE markets TYP200 as race capable. They do not do that with SL6, their LV fluid.

 

[nthach]

I've been using DOT 4 LMA(Castrol, Valvoline, ATE Type 200) as SOP on any brake service - lately I've been using DOT 4 LV with no ill effects. However, someone gave me a bottle of Wagner DOT 5.1 and that was used to flush out the brakes on an old Explorer that never saw frequent brake fluid changes.

 

[Falcon_LS]

There are two types of DOT 4 brake fluid DOT 4 and DOT 4LV. LV is low viscosity. DOT 4LV has been/is used in many new Ford vehicle's, every F150 included. Euro makes also switched to DOT 4LV.

The LV is good for ABS equipped vehicles. Otherwise DOT 4 or DOT 5.1 will work perfectly fine.

 

[edyvw]

The LV is good for ABS equipped vehicles. Otherwise DOT 4 or DOT 5.1 will work perfectly fine.

LV is developed for ESP operation. ABS vehicles are perfectly fine with normal viscosity.

 

[Jetronic]

Nothing. In fact dot5.1 esp has the same viscosity requirements as dot4 LV last time I checked. At 100C or 212F all synthetic brake fluids meet the same minimum viscosity. But dot 5.1 can contain up to 70% silicone so can lead to a softer pedal like dot 5.

Likely ESP/ABS works better at regular temperatures with a lower viscosity fluid aswell, what's the point in being able to cycle valves 25 times per second if the pressure won't bl;eed off fast enough. Older generations of ABS/ESP cycled about half as fast.

 

[BHopkins]

Nothing. In fact dot5.1 esp has the same viscosity requirements as dot4 LV last time I checked. At 100C or 212F all synthetic brake fluids meet the same minimum viscosity. But dot 5.1 can contain up to 70% silicone so can lead to a softer pedal like dot 5.

Likely ESP/ABS works better at regular temperatures with a lower viscosity fluid aswell, what's the point in being able to cycle valves 25 times per second if the pressure won't bl;eed off fast enough. Older generations of ABS/ESP cycled about half as fast.

Fascinating. I didn't know that 5.1 can contain silicone.

I'm reasoning that the new Bosch brake fluid, which is labeled as DOT 3, DOT4, DOT5.1, meets the viscosity and wet/dry boiling points of 5.1, but does not contain silicone. If it did, it couldn't be labeled DOT3 and DOT 4. Is this correct?

 

[demarpaint]

Any thoughts on the valvoline “synthetic” dot 3&4 fluid? I’ve been using it for years and it’s always been fine but I can’t seem to find any actual specs on it now. Just their separate dot 3 and dot 4 fluids.

That has been my go to for quite a while.

 

[NYEngineer]

Fascinating. I didn't know that 5.1 can contain silicone.

I'm reasoning that the new Bosch brake fluid, which is labeled as DOT 3, DOT4, DOT5.1, meets the viscosity and wet/dry boiling points of 5.1, but does not contain silicone. If it did, it couldn't be labeled DOT3 and DOT 4. Is this correct?

I believe 5 is silicone and 5.1 is not.

 

[SuperSalad]

5.1 cannot contain silicone. Only DOT 5 may contain silicone.

There is no mention whatsoever of a DOT 5.1 being able to contain up to 70% silicone. It specifcally says, DOT 5.1 must be labelled as Non Silicone Based

What it does say is:

"A silicone base brake fluid (SBBF) is a brake fluid which consists of not less than 70 percent by weight of a diorgano polysiloxane."

Meaning a DOT 5 must contain at least 70% silicone, not that a DOT 5.1 may contain up to that amount.

It specifically does mention compatibility requirements:

"S5.1.10 Compatibility. (a) At low temperature. When brake fluid is tested according to S6.10.3(a), the test specimen shall show no sludging, sedimentation, or crystallization. In addition, fluids, except DOT 5 SBBF, shall show no stratification."

That would mean DOT 5.1 would be subject to those compatibility requirements, which in turn disqualifies silicone as a constituent since it would stratify.

Here is the regulation in full: Title 49 CFR Part 571.116

 

[BHopkins]

5.1 cannot contain silicone. Only DOT 5 may contain silicone.

There is no mention whatsoever of a DOT 5.1 being able to contain up to 70% silicone. It specifcally says, DOT 5.1 must be labelled as Non Silicone Based

What it does say is:

Meaning a DOT 5 must contain at least 70% silicone, not that a DOT 5.1 may contain up to that amount.

It specifically does mention compatibility requirements:

That would mean DOT 5.1 would be subject to those compatibility requirements, which in turn disqualifies silicone as a constituent since it would stratify.

Here is the regulation in full: Title 49 CFR Part 571.116

What you are saying is what I have always understood until studying up after reading what Jetronic said above. And reading through the specification, I could find nothing at all that prohibits DOT 5.1 from containing up to 70% silicone. The only definitions of content that I could find is what you quote above in regards to DOT 5, and a definition for mineral oil brake fluid. It would seem that DOT 3, DOT 4, and DOT 5.1 can contain anything as long as they meet the specifications outlined in S5. With the exception of what is spelled out in the S4 definitions.

I did find safety data sheets for 5.1. One from Brembo and another from Liqui Moly. Neither made any mention of silicone.

And It doesn't make any rhyme or reason that that DOT 5 could be made up of 71% silicone, DOT5.1 could be made up of 69% silicone, yet going from one to the other requires an entire purge and cleaning of a brake system.

 

[SuperSalad]

What you are saying is what I have always understood until studying up after reading what Jetronic said above. And reading through the specification, I could find nothing at all that prohibits DOT 5.1 from containing up to 70% silicone. The only definitions of content that I could find is what you quote above in regards to DOT 5, and a definition for mineral oil brake fluid. It would seem that DOT 3, DOT 4, and DOT 5.1 can contain anything as long as they meet the specifications outlined in S5. With the exception of what is spelled out in the S4 definitions.

I did find safety data sheets for 5.1. One from Brembo and another from Liqui Moly. Neither made any mention of silicone.

And It doesn't make any rhyme or reason that that DOT 5 could be made up of 71% silicone, DOT5.1 could be made up of 69% silicone, yet going from one to the other requires an entire purge and cleaning of a brake system.

I see what you are saying, but there is a problem with that thought process which I tried pointing out.

Yes, on paper, there is nothing specifically prohibiting a DOT 5.1 from containing silicone. However in reality, no diorgano polysiloxane containing brake fluid could pass the "no stratification" requirement in the compatibility testing. So there is functionally no way you could pass the DOT 5.1 requirements with a silicone containing brake fluid. This makes it so silicone is only able to be used for DOT 5 since DOT 5 is the only type exempt from that "no stratification" requirement.

 

[Jetronic]

I'm glad to read that.

Using dot4 LV anyway as that's what the manufacturer demands

 

[BHopkins]

I see what you are saying, but there is a problem with that thought process which I tried pointing out.

Yes, on paper, there is nothing specifically prohibiting a DOT 5.1 from containing silicone. However in reality, no diorgano polysiloxane containing brake fluid could pass the "no stratification" requirement in the compatibility testing. So there is functionally no way you could pass the DOT 5.1 requirements with a silicone containing brake fluid. This makes it so silicone is only able to be used for DOT 5 since DOT 5 is the only type exempt from that "no stratification" requirement.

Great explanation. Thank you for taking the time to share it.