Which brake fluid?

[RoadRacer]

What fluid is the current recommendation?

The last time I built a car (GTD40) I remember a lot of "discussion" over DOT numbers - some being more/less hygroscopic, higher boiling point etc. I remember that the DOT relates to boiling point, so I was using 5.1 because I tracked the car a lot, and it seemed the best at the time.

But I've heard since then that it was a bunch of baloney, and that DOT 4 was just as good than 5.1, and better in some ways (like compressibility).

What does everyone use today?

[David Hodgkins]

I don't track my car, except very occasionally.

I use dot 3. Works fine for canyon carving.

:)

[GoDadGo]

I've got DOT-4 in my daily driver and the MK-4; however, it is only because it is required over at NOLA Motorsports Park in order to play on their track.

If this wasn't the case, I'd have no need for DOT-4 fluid.

[RoadRacer]

I've got DOT-4 in my daily driver and the MK-4; however, it is only because it is required over at NOLA Motorsports Park in order to play on their track.

If this wasn't the case, I'd have no need for DOT-4 fluid.

Thanks - that's still a great data point because other tracks may have similar requirements. Today I'm only considering 4 or above but I'd love to hear all opinions.

[Mountain-Metalworks]

A bunch of the decision goes to what you're going to use the car for. If it will see occasional autocrossing/track, heavy road course time, or just regular/spirited driving. I expect my car to be somewhere in the occasional to heavy track time and I did a TON of research on this(many hours over the course of several days). I ended up going with ATE DOT4 fluid for it's boiling point capabilities, etc...

https://www.amazon.com/gp/product/B003VXRPL0/ref=oh_aui_detailpage_o01_s00?ie=UTF8&psc=1

It's rated way better than Wilwood's own fluid in their braking system. In fact the Wilwood has poor compatibility with other high quality fluids so if you change you can get some cross contamination.

Again, if it's a daily driver I'd stick with a regular old DOT3 or 4 fluid from a decent brand. i.e: don't go with Farm and Fleet brand or something not intended for at least a passenger/sports car.

-TJ

[edwardb]

I've used Valvoline DOT 3 & 4 synthetic brake fluid in all my builds. Highly rated, available nearly everywhere, reasonably priced. Unless you have very specific requirements or rules, really no reason to get exotic. Never an issue for my mostly street driving. http://www.valvolinechemicals.com/products/valvoline-dot-3-and-4-brake-fluid.

[idf]

The table below is from the Pegasus catalog:

Brake Fluid is rated by dry boiling point (for fluid fresh out of the bottle) and wet boiling point (for fluid saturated with moisture). If you bleed brakes frequently, the dry boiling point is most important. If you do not change your brake fluid often, the wet boiling point becomes more important. All of our fluids (except AP Radi-CAL R2) will mix with DOT 3, 4, and 5.1 fluids. None of the fluids we carry are compatible with DOT 5 (silicone) fluids.



Racing Brake Fluid Comparison Chart


Brand Name
DOT
Rating
Dry
Boiling
Point
Wet
Boiling
Point
Compatible with
Conventional
Brake Fluids*
Qty
Fl Oz
Part
Number


Motul RBF 660
4
617
399
Yes
16.9
MT660


AP Radi-CAL R3
(formerly PRF)
4
608
399
Yes
16.9
3338-17oz


Red Line RL-600
4
604
400
Yes
16
RL600


Motul RBF 600
4
594
421
Yes
16.9
MT600


AP Radi-CAL R2
(formerly Super 600)
n/a
594
399
* No *
16.9
3309-17oz


Castrol SRF
4
590
518
Yes
33.8
3343-Liter


Prospeed RS683
4
583
394
Yes
16.9
3340-201


ATE Type 200
4
536
396
Yes
33.8
3327-Liter


AP Radi-CAL R1
(formerly AP 551)
3
516
284
Yes
16.9
3305-17oz


Castrol Advanced Performance
(formerly GT-LMA)
4
509
(was 446)
329
Yes
12
3308-12oz



* None of the brake fluids we carry are silicone-based or compatible with silicone-based fluids.