brake fluid

[sharki786]

Which is better for long run (4-5 years) dot 4 or dot 5.1?
Thanks

[trog_nfs]

Dot 4 is less hygroscopic than Dot 5.1, so it will last longer.

[sharki786]

Dot 4 is less hygroscopic than Dot 5.1, so it will last longer.

Sorry mate but what does that mean??

[thai-wronghorse]

Basically it'll absorb less water (moisture from the air) therefore not allowing the efficency of the brake fluid to diminish as quickly . 

[Khare]

You're getting it wrong.

Dot 3, dot 4 and dot 5.1 are poly glycol compounds and dot 5 is silicone.

It's dot 5 that does not absorb water, but silicon is more compressible and hasn't got the lubricating properties of poly glycol so it needs to be used in a system that is designed for dot 5. Dot 5.1 is best for our cars for fast road/track, but it's expensive compared to dot 4, which unless you're real heavy on the brakes will be good enough for fast road.

[VW BUSH]

You're getting it wrong.

Dot 3, dot 4 and dot 5.1 are poly glycol compounds and dot 5 is silicone.

It's dot 5 that does not absorb water, but silicon is more compressible and hasn't got the lubricating properties of poly glycol so it needs to be used in a system that is designed for dot 5. Dot 5.1 is best for our cars for fast road/track, but it's expensive compared to dot 4, which unless you're real heavy on the brakes will be good enough for fast road.

Correct, glycol based fluids are hygroscopic and are used to preserve rubber seals and flexi's in the braking system.
Silicone and and mineral oils are not suitable for use with conventional seals or junctions in the braking system.
Just use standard brake fluid and bleed it through well, I change mine with every pad change as its easy and cheap to do.

[sharki786]

Thought id bump this up. As some may know im sorting my whole braking system out. Im going to be refurbing the calipers and replacing the rears with mk4 calilers. My braided line kit is on its way and have yellow stuff pads & groovesd discs.
What my question is which dot 5.1 should i use? Any brands?

Thanks peeps

[boneybradley]

dot 4 will be fine, i have even used it on a few track days without fade/boiling it

[sharki786]

Reason i want to use 5.1 is because i use my breaks hard and now im getting brake fade. So want to try out 5.1.
Motul 5.1 good shizzle?