Brake Fluid

[Lee]

I am currently using Castrol Super Dot4. Works very well and took huge punshment during a recent trackday without exhihiting any spongyness. When I change my rear calipers later this year I will change it to Castrol SRF, using 2 litres. One to flush the old stuff out and 1 litre for the system itself. SRF does not mix well. Problem is, SRF is at least 35 quid a litre but it's excellent stuff. It is blue in colour.

[dan_b]

Racing fluids are designed for excellent dry boiling points, and with little regard to wet boiling points I imagine, because the assumption is a racing fluid would be changed extremely regularly?

This is all very confusing!

[Lee]

I change my fluid annually as a service job.

[dan_b]

Fair enough. Probably the best thing to do really.

[dan_b]

Anyone tried the EBC brake fluid by the way? Anyone know anything about it?

[Pete_RS2]

I need to top-up my brake fluid as it's on the MIN mark & the Autocheck warning lamp is flashing. As I don't know what fluid is currently in there is it OK to mix DOT4 & DOT 5.1 ? I'll get it changed ASAP but I just want to stop the Autocheck bleeping & flashing at the moment.

[Stick Insect]

I need to top-up my brake fluid as it's on the MIN mark & the Autocheck warning lamp is flashing. As I don't know what fluid is currently in there is it OK to mix DOT4 & DOT 5.1 ? I'll get it changed ASAP but I just want to stop the Autocheck bleeping & flashing at the moment.

Peter, I would personally put a higher grade fluid in i.e. 5.1. If you get a big container of it then you can bleed your brakes later and do the job properly.

David

P.S. please don't sue me if I have given lousy info......

[AbsS2]

Is it safe to mix DOT 4 with DOT 5.1?

[rotoryboy]

Just don't use dot 5

[Lee]

Stick with DOT4. Be careful with different types of DOT5 and 5.1 as they are not all compatible with our system. Don't mix different fluids as you can get reactions that form crystals in the fluid.
I recomend a full flush and fill with Castrol Super Response DOT4 for £10 per litre from Halfords. Hard to beat and I used it for 2 years with heavy road and track use...no fade whatsoever. Bargain product. But then I do have very big brakes so my peak fluid temperatures are quite low comparatively. I think Doug used it too with good results.

[caterpillar]

I always use dot 5,0 or 5,1 because they DON't have the rustprob.they dont take up the vater in the air....!!!

[Lee]

I didn't think that DOT 5 was compatible with the seals used in the standard S2 system. DOT5 is not necessarily better than DOT4 because of the higher number, it just meets different specs.

[Alistair C]

I always use dot 5,0 or 5,1 because they DON't have the rustprob.they dont take up the vater in the air....!!!

I think 5.1 is safe to mix with anything - certainly on a temp basis.
5.0 you definately don't want to use in the S2.

[rotoryboy]

I didn't think that DOT 5 was compatible with the seals

Nope. It will def. kill the seals in the S2

[dan_b]

Absolutely don't EVER use DOT 5 -this is based on a silicone-fluid, rather than a mineral oil-based fluid that our cars need, you'll destroy the braking system.

DOT5.1 is, however, absolutely fine. Some half-assed naming scheme really.

DOT5.1 has a higher minimum specification for boilng points than does DOT4, but that does not mean that all DOT5.1 fluids are superior to DOT4s...

The ATE Super Blue fluid exceeds the DOT5.1 minimum spec for dry boiling point by some margin, but is not registered as a DOT5.1 because it is coloured!

I'm using Halfords DOT5.1, and have had no fade problems at all, even on track. I may change to a Castrol SRF, or ATE Super though just for the hell of it. The nice thing about the ATE fluid is that it is coloured (either Gold or Blue) so that it's easier to see when you're pulling new fluid through the system.

I think the only down-side to the ATE fluid is that it's rather hydroscopic so absorbs water fairly fast, so you need to change it more regularly.