Mike1982

I have hear that I should use brake fluid DOT 4 for our cars, but was is the difference in all of them? DOT 3, 4, 5, ATE super blue? I would like to hear what is the difference in them.

Brian McCoy

DOT 3,4,5.1 are all Glycol based, hygroscopic (attracts/absorbs water) and have definitive wet/dry boiling points. You can use ANY of these in your system, but it's generally best to look for the highest boiling points (this is what determins where fade occurs as fade is just water in the system boiling). The higher the boiling points, the more expensive (generally) ~ buy the best you can afford ~ or stick with ATE as it's a known fluid and highly recomended.

DOT 5 is silicone based, is NOT compatable with the above and if you swap DOT5 into a DOT3/4/5.1 system, you'll likely have catostrouphic failure at the seals.

roy_josef

Best value for money in my opinion is ATE Dot Blue.

jim944s2

I've always had very good results w/ Motul 600 as well.

MHT

ate superblue is dot 4 with a high boiling point, ate typ200 has same wet/dry boiling points but is gold instead of blue. Whatever you use, flush the system regularly to avoid expensive repairs. The moisture in the fluid causes corrosion inside the system and can lead to calipers sticking and master cyls failing.

jabbadeznuts

W88951

I fully agree with the Ate Super Blue. Go with the Motul RBF 600 if you want the best performance, but at twice the price of Ate it is really not worth it on the street.

944Willie

I had Dot 5 in my bimmer the whole time it was in storage (5 years) and in was clean as could me when I started tracking it again. No moisture, no coloration, nothing. I didn't have to touch my brakes (excluding the inspection) prior to getting on track.

Sami951

Yeah, there are some good things about Dot 5, like that it doesn't absorb moisture ... but ...

IT IS NOT COMPATIBLE WITH DOT4 ETC REGULAR FLUIDS

... ie., it doesn't mix with them, and since it has different additives (can't remember which way it went, either to keep seals from contracting or swelling, but exactly the other way than normal brake fluids), you will lose seals. -> expensive $$$. Just say no! (you can also ask me how I know)

Get good quality Dot 4, like ATE Super Blue, or even Porsche OEM stuff (white cans at the dealer). Can't remember if it's expensive or not, but it's damn good...

edit: That's to say changing from dot4 to dot5 is a recipe for disaster. A system filled with dot5 from new works fine, if you enjoy having a spongy pedal no matter how much you bleed the damn thing.

Matt H

If you change components frequently and just like to be different ANY hydraulic fluid can be used. If you remember the 951 on SpeedChannel the other day, they could have solved their boiling problem by using Synthetic motor oil instead of brake fluid. You would need to check it often and probably rebuild two times a year but if you like to be different, anything can be used :>)
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Skip

I wouldn't recommend the motor oil - have heard that one before, and lots of reasons not to, especially in ABS systems. Corner-Carvers has an excellent thread regarding this.

The team running the 951 on Speed knew exactly why they were having trouble, and they likely know by now how to resolve it. They need to wrap the Turbo and pipes and also the brake MC/Reservoir with quality heat wrap. Standard practice for 951 race cars.

Matt H

Skip - many a high end race car is using Mobil 1 in the Res. I dont recommend it for the street either, actually I think it would make youa moron but to each his own! Since the ABS system on these car is archaic I doubt it would hurt anything. On a newer Teves 4 system it MIGHt cause problems. There is a Koni rebuilding thread you need to look at on here, should be on page 1/2. Since we didnt address his question, ATE Super Blue or Motul 600 is what I generally use.
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Matt Romanowski

The Early 911S Registry has a nice table of all the fluids and their wet and dry boiling points. Check out: http://members.rennlist.org/911pcars/brakefluid.htm

Matt

Mark Parker

Yes, for long term storage (5 years f'rinstance) DOT5 would be ideal, which is the primary reason it's used in military stuff. But it will absolutely not mix with 3 and 4. Also, IIRC from my days trying to maintain British Leyland stuff which used Girling hydraulics, DOT4 was required in those because they used natural rubber cups which would deteriorate with 3. I believe also that DOT 4 is backward compatible for synthetic rubber goods.