Bestest brake fluid

[Quickstep192]

I hope this doesn’t spark a religious debate, but I’m looking for a brake fluid recommendation for my ‘73 911 T.

I don’t track the car, but I’ve rarely found issue with using the best/most robust product, even if all of its capabilities don’t get leveraged.

I’ve read about Motul 660 and ATE TYP200

Are there others to consider?

[GH85Carrera]

I have used the ATE Type 200 for 27 years in my 911. I change the brake fluid every single spring, without fail. I still have the OEM original master cylinder. The guys that track the car say the Tyoe 200 is not good enough, but I have tracked my car many times and had no issues, but my car is a street car, not a trailered track whore, and I don't push to the limits.

For your car, ATE is just fine.

[DWeg1998]

The ATE 200 should work well for you. I go to a track once a year and it couldn’t hold up without boiling on me so I went to Motul 600 and that has worked so no need to pay for Castrol SRF.

[HarryD]

I have used ATE typ 200 for over 20 years. Spirited driving, autocross, HPDE. Never let me down. Like Glen, I flush my fluid annually. Still on same MC.

[Quickstep192]

To me, paying extra for the next level product is “cheap insurance”.

I probably won’t be are ardent about annual fluid changes as you guys are. Given that, is the Castrol SRF worth what seems like just a few extra bucks?

[DWeg1998]

SRF is way over kill and more than a small price difference

[DWeg1998]

On Amazon-
ATE 200- $18 for a full litre
Motul 600- $20 half litre
Motul 660- $28 half litre
Castrol SRF- $59 half litre

[drtyler]

ATE 200, Pentosin DOT 4, Brembo DOT 4, Castrol DOT 4 are all good quality brake fluid choices.

Fresh is best when it comes to brake fluid.

[winders]

ATE Type 200 is perfect for a street car. In my race car I use Brembo HTC 64T which is better than Castro SRF. But, I would never use that in my street car as I would be wasting money and not gaining anything.

[stownsen914]

"Better" brake fluid usually means more resistance to boiling at high temperature. You'll not do this under any normal circumstance in a street car, so I dont see any advantage. I'm not aware that the more expensive brake fluids are better in other ways, but maybe I'm missing something. In a street car I'd use a quality brake fluid like Ate 200 and flush regularly.

[PeteKz]

Use a brake fluid tester to measure moisture content. That's more important than what brand you use. Part of what you pay for in a premium brake fluid is a lower starting moisture content. According to some other folks here, some of the popular brands and FLAPS house brands have 1.5% right out of a fresh bottle. In other words, they are already halfway used up!

[Bill Verburg]

You want DoT 4

other than that the big differences are wet and dry boiling point specs

for stressed brakes unless the fluid is changed daily go by wet

for street use ATE200 is fine and factory fill on most German cars

sorted by wet boiling points from highest to lowest

[brp914]

I wish ATE would sell the blue dye they used put in their fluid. Kind of surprised they don't. Or maybe a dye that has variable color depending on % moisture.

[HarryD]

Originally Posted by brp914

I wish ATE would sell the blue dye they used put in their fluid. Kind of surprised they don't. Or maybe a dye that has variable color depending on % moisture.

DOT does not allow any dyes in brake fluid. Not a decision by ATE. The blue was marketed as “not for Street use”.

When I alternatively used the blue/gold fluid, I noticed that the furthest cylinder needed about 180 ml to make a color change. The closer ones less.

[brp914]

Understood. I wish they would sell the dye separately.

[brighton911]

An easy and accurate way to test brake fluid is with your multimeter. Set to low scale on DC volts, put the positive probe in the MC and in contact with the brake fluid. The negative probe goes to battery ground. Any reading over .3 volts means the brake fluid has absorbed excess water and should be changed.

[Quickstep192]

So, in however many years it’s been, no one has managed to make a brake fluid that’s not hygroscopic?

[GH85Carrera]

Originally Posted by Quickstep192

So, in however many years it’s been, no one has managed to make a brake fluid that’s not hygroscopic?

Water is the universal solvent. The old adage water and oil don't mix is wrong, look at the "milk shake" goo on a engine oil fill cap that does not get hot enough for long enough.

To design a fluid that can lubricate the rubber seals and keep them pliable, and withstand the high heat of brake calipers and still stay liquid and useful in minus 50 temps is just not an easy task. I am not a chemist at all, but even if some company made a new super brake fluid, would it be compatible with current fluids, or require a total rebuild and replacement of all part?

What if the driver is on the road and has a leaking brake line and needs to top off the fluid? If he pours in the fluid at every gas station or convenience station will it wreck his fluid?

And it HAS to be a clear of very light honey color to be DOT legal. Oh and it can't cost $500 per liter or no one will buy it.

Just change the fluid each spring, cheap and easy. Done.

[HarryD]

Originally Posted by GH85Carrera

Water is the universal solvent. The old adage water and oil don't mix is wrong, look at the "milk shake" goo on a engine oil fill cap that does not get hot enough for long enough.

To design a fluid that can lubricate the rubber seals and keep them pliable, and withstand the high heat of brake calipers and still stay liquid and useful in minus 50 temps is just not an easy task. I am not a chemist at all, but even if some company made a new super brake fluid, would it be compatible with current fluids, or require a total rebuild and replacement of all part?

What if the driver is on the road and has a leaking brake line and needs to top off the fluid? If he pours in the fluid at every gas station or convenience station will it wreck his fluid?

And it HAS to be a clear of very light honey color to be DOT legal. Oh and it can't cost $500 per liter or no one will buy it.

Just change the fluid each spring, cheap and easy. Done.

Great points.

FWIW there is DOT 5 fluid which is not Hydroscopic but typically does not give the firm feel we need and expect. Interesting read on the topic: https://www.gomog.com/allmorgan/brakefluids.html

[Otter74]

Water is not soluble in oil. The milkshake you see when, say, you have a leaking head gasket is an emulsion, like mayonnaise.

Originally Posted by GH85Carrera

Water is the universal solvent. The old adage water and oil don't mix is wrong, look at the "milk shake" goo on a engine oil fill cap that does not get hot enough for long enough.

To design a fluid that can lubricate the rubber seals and keep them pliable, and withstand the high heat of brake calipers and still stay liquid and useful in minus 50 temps is just not an easy task. I am not a chemist at all, but even if some company made a new super brake fluid, would it be compatible with current fluids, or require a total rebuild and replacement of all part?

What if the driver is on the road and has a leaking brake line and needs to top off the fluid? If he pours in the fluid at every gas station or convenience station will it wreck his fluid?

And it HAS to be a clear of very light honey color to be DOT legal. Oh and it can't cost $500 per liter or no one will buy it.

Just change the fluid each spring, cheap and easy. Done.