Best mid-grade brake fluid

[Nartard]

I'm getting ready to put on Neuspeed's 2 piece rotors front and back, along with a new set of brake lines to the calipers. While I'm in there, I'll do a full flush on the fluid since it's due. What's a solid fluid to use? I run the car on the dragstrip only, no real heavy demand like road courses. I need to go from 130-0 in short order, with plenty of cool down times.

Here's what I've gleaned from other threads:
Castrol SRF Silicone based - expensive but doesn't require a lot of changing out.
Motul RBF 600 / 660 glycol based - cheaper, but very hydroscopic and needs to be changed annually at minimum.
Regular Dot 4 - 2 year change cycle, lower boiling points.

Will the SRF damage any components if I went that route? I understand that it requires a complete purge, and cannot be mixed. How sensitive is the Motul to moisture absorption?

[Potatohead_RS3]

For that usage case I would use plain old dot 4

[ECS Tuning-Audi]

For your use, good old Super DOT4 from Pentosin would be my suggestion.

https://www.ecstuning.com/Audi-RS3-8...Braking/Fluid/

-James

[mbar]

For mid+ level performance I would use ATE.

[Nartard]

Is there in fact a relationship between high boiling points and shorter fluid life? (On glycol fluids)

[WheeRS3]

Castrol SRF is not silicone based and is compatible with DOT 3, 4, and 5.1. You can mix it if you want (not that you would).

My understanding is Motul RBF600 is better than 660 due to its wet boiling temp (which is more important as it absorbs water).

There's also Motul 5.1 which is their standard DOT 5.1 fluid if you want to consider that.

[Nartard]

Castrol SRF is not silicone based and is compatible with DOT 3, 4, and 5.1. You can mix it if you want (not that you would).

My understanding is Motul RBF600 is better than 660 due to its wet boiling temp (which is more important as it absorbs water).

There's also Motul 5.1 which is their standard DOT 5.1 fluid if you want to consider that.

Appreciate that, seems I may have been misinformed on SRF somewhere on the interwebs. The aforementioned Pentosin seems like an option for my needs, as does the Motul 600.

[MacFady]

Motul RBF 600 / 660 glycol based - cheaper, but very hydroscopic and needs to be changed annually at minimum.

Hygroscopic, hydroscopic refers to looking at things under water.

[o1turbo30v]

Id go with Amsoil if you have an account with them, throw that in your cart the next time you order oil, if not, Pentosin Super DOT 4 from your local Autozone.

[Nartard]

Hydroscopic. That's how I'm starting to feel about brake fluids, lol. More to it than initially expected.

[RSKYBET]

Castrol SRF is not silicone based and is compatible with DOT 3, 4, and 5.1. You can mix it if you want (not that you would).

Glad somebody already pointed this out. Silicone (DOT5) does not equal silicon. According to Castrol, SRF is “silicon ester based”.

My recommendation would be for a lower viscosity brake fluid like ATE SL.6 because of our cars ABS and traction control systems.


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[RSKYBET]

*deleted*

[Potatohead_RS3]

My recommendation would be for a lower viscosity brake fluid like ATE SL.6 because of our cars ABS and traction control systems.

I was going to mention this in my post. I don't know how important it is because unless you are doing a full flush with VCDS or similar you aren't draining the abs pump of the old fluid. But, it's probably a good idea.

[OE2]

https://www.lelandwest.com/brake-flu...ison-chart.cfm

[Nartard]

I was going to mention this in my post. I don't know how important it is because unless you are doing a full flush with VCDS or similar you aren't draining the abs pump of the old fluid. But, it's probably a good idea.

Forgive my ignorance again. Will a higher viscosity fluid degrade ABS performance in cold temps, or is it only a problem for flushing the lines (sans VCDS)?

[Potatohead_RS3]

Forgive my ignorance again. Will a higher viscosity fluid degrade ABS performance in cold temps, or is it only a problem for flushing the lines (sans VCDS)?

I have used both and noticed no difference in performance. I believe the reason for the thinner fluid is there are many small passageways in the abs pump. I think enough people use regular fluid without issue that it's no big deal, but if you can get the right stuff that's probably the best option. In terms of flushing and bleeding I wouldn't expect any difference really.

[Nartard]

Pulling this back up as I plan on completing my braking project mid-week.

I have the Motive power bleed setup - puts pressure / fluid in from the master cylinder while bleeding from each corner. Do I need to put the car into 'brake bleed mode' from VCDS? Does anybody know what this actually enables?

[Nartard]

Pulling this back up as I plan on completing my braking project mid-week.

I have the Motive power bleed setup - puts pressure / fluid in from the master cylinder while bleeding from each corner. Do I need to put the car into 'brake bleed mode' from VCDS? Does anybody know what this actually enables?

Turns out Google and RossTech wiki have a ton of info on this proceedure. Should of searched first.

[Potatohead_RS3]

Planning on bleeding when swapping winter tires to summer here in a couple weeks, picked up some of the Pentosin DOT4 LV

I could have sworn I read somewhere months ago that some people bleed these cars backwards, like LF to RR. Is that just hogwash? I've always done pretty much every car RR to LF.