What DOT clutch/brake fluid to use on 94 SS

[greg donovan]

i know you are supoposed to use brake fluid in the clutch res. and i thought you were supposed to use the same stuff you use in the brake res.

however, the brake res. says to use DOT 3 or 4 while the clutch only says to use DOT 3.

i only have some DOT 4 stuff. is that a no-no to use DOT 4 in the clutch res.?

[Legacy777]

DOT 3 or 4 is fine.

[BAC5.2]

They are backwards compatable. DOT4 exceeds DOT3 standards, and may be used in a DOT3 system.

DOT 3 may not be used in a DOT4 system.

[greg donovan]

They are backwards compatable. DOT4 exceeds DOT3 standards, and may be used in a DOT3 system.

DOT 3 may not be used in a DOT4 system.

thanks.

that what i thought but wanted to be sure.

so, DOT3 or DOT4 is ok in a DOT3 or a DOT3/4 but only use DOT4 in a DOT4 system and DOT5 is right out.

[BAC5.2]

Right. Scott would know for sure, but I think DOT5 is silicone based, and is not for car brake use, and DOT5.1 is the stuff used in brake systems.

I believe DOT5.1 is backwards compatable, so you could probably use it in your system.

FWIW, I run Superblue for my brakes, and I'll probably run the same for my clutch.

[scottzg]

Dot 5 is silicon based, right. Its used in the military vehicles, and it compressible- not ideal for cars anyway.

Dot 3/4 are more or less the same, albeit with slightly different properties and dot 3 minimum requirements are lower. Dot 5.1 is dot 4 fluid that meets dot 5 specs for boil resistance. It is backwards compatable with dot 3/4.

[greg donovan]

is DOT5.1 that much better?

[BAC5.2]

It might be, but I doubt it. I wouldn't bother trying to source high quality DOT5.1 when super high quality (and super blue) DOT4 is readily available for barely any money.

[Legacy777]

The only other thing to mention is that DOT 4 & 5.1 brake fluids are more hygroscopic then DOT 3. So with a given amount of time, DOT 4 & 5.1 fluids will absorb more water then the DOT 3 fluid.

The introduction of water in the system will lower the boiling point. So after an extended period of time, the higher boiling points of DOT 4 & 5.1 fluids may be a mute point. They do however typically have higher wet boiling points.

I would say the reason they call for DOT 3 fluid in the clutch setup is because it does not get changed very often.

[greg donovan]

The only other thing to mention is that DOT 4 & 5.1 brake fluids are more hygroscopic then DOT 3. So with a given amount of time, DOT 4 & 5.1 fluids will absorb more water then the DOT 3 fluid.

The introduction of water in the system will lower the boiling point. So after an extended period of time, the higher boiling points of DOT 4 & 5.1 fluids may be a mute point. They do however typically have higher wet boiling points.

I would say the reason they call for DOT 3 fluid in the clutch setup is because it does not get changed very often.

well that makes sense.