brake fluid recommendations

KaienZ34

I know we can't run dot 5, what about Motul 5.1 ?

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JARblue

Yes. Motul 5.1 is fine. AFAIK, Dot 4 is compatible with 5.1 - the one you have to watch out for is Dot 5 which is silicone based and incompatible.

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Chris_B

DOT 5.1 is chemically compatible with DOT 4, but it's not ideal to mix them. 5.1 has a lower viscosity specific to ABS systems. The thinner fluid helps the valve response, yet it doesn't provide the same pedal feel as the best DOT 4 fluids.

If you track the car at all, it's worth spending a few extra bucks for a top fluid (like the best, Torque RT700) as you won't have to flush it nearly as often. Some teams I work with are getting 3-4 times the life, a few even more. Their crew is very happy they don't need to flush every day at the track.

If your car rarely sees the track, look for the cheapest fluid with the same specs as the Motul product. After all, it will be the same exact fluid made in the exact same UK factory as theirs is. Only the bottle is different.

Chris

synolimit

rbf600 is best hands down. in this case i wouldnt reinvent the wheel and just get what works.

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13 370z-

JARblue

While the RBF600 is great fluid, I don't think there's any doubt that there are better fluids out there. Castrol SRF and Torque RT700 both have higher wet and dry boiling points

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Chris_B

AND better feel (due to a higher specific gravity and less dissolved air), and better reserve alkalinity, and more stable pH, and better resistance to the negative effects of moisture absorption (hygroscopicity), and...

RBF600 is definitely old school at this point and, for what it is, overpriced. The exact same fluid is found for half the price elsewhere. RBF660 is a little better (also made for Motul by the same company), but does not approach SRF, much less RT700.

Chris

synolimit

Maybe I'm slow, but how exactly does it "not approach" when its over for the number that counts?

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13 370z-

Chris_B

Not slow at all. It is important to know that boiling point alone does not define a better brake fluid. Yes, higher is generally better, but things like specific gravity, retained moisture, reserve alkalinity, etc., do matter. Normally, RBF600 (or even RBF660) must be changed regularly when used aggressively. While RT700 does have a higher boiling point, it also has a noticeably better pedal feel (less compressible) and can be run longer, making the higher initial cost negligible. Some teams I work with are saving a little money, yet they are also saving time, which is more valuable at the track. Bleeding the brakes takes time away from more productive activities.

While the Motul product has been marketed very successfully for 30-something years, better options have been on the market for quite some time now. Since the company that makes their brake fluids also sells the very same chemicals to almost 3 dozen other companies, there is no claim to superiority that can be supported. Fortunately for enthusiasts, better brake fluid is not really that expensive as compared to the other things we should be spending money on.

Chris

synolimit

Let's say all around then. RBF600 to me is $12 or something a bottle while SRF is $35 but I only see 1000mL so you have to pay out $70 and RT700 is $34. And for the Castrol SRF the dry is actually lower by 4 degrees unless you're doing hour long racing wheel to wheel like the Pirelli world c or conti with doran, save the money. 20min sessions aren't going to show any improvement. My 0.02

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13 370z-