DOT 5 Brake Fluid

[Patrolman]

I had never heard of DOT 5 until watching MotorWeek (episode 3425) yesterday. It is apparently a new brake fluid, which unlike other types, does not attract moisture. That means that the brake components can last longer, and the fluid can remain in the system longer.

Important to know though is that it apparently will not work with ABS brake systems as it will bubble. This means that can likely only be used in older vehicles (a plus for me) or in hydraulic clutch systems. My understanding is that it can be used in any system requiring DOT 3 or DOT 4, but again, not in ABS. It is also considerably more expensive, but if it lasts longer, over the long run it may end up cheaper. Oh yeah, and it is PURPLE! :)

Here is some good info:

http://en.wikipedia.org/wiki/DOT_5

http://www.motorweek.org/features/goss_garage/brake_fluids_and_abs

[94ToyBear]

I heard new Harleys use dot 5, from my understanding it's for High temp break systems and will only work for dot 5 applications only no dot 3 or 4 is compatible because it's a silicone base fluid.

BUT I might be of on the facts. I never used it in an automotive application.

[Patrolman]

This is what was quoted in Wikipedia, and as we know, everything on the internet is always correct. :)

"Using DOT 5 in a DOT 3 or DOT 4 system without proper flushing will cause damage to the seals and cause brake failure. DOT 5 brake fluid is not compatible with anti-lock brake systems."

[Jim]

I ran DOT5 / Silicone in my 68 Ford Ranch wagon - after I replaced all four wheel cylinders (and maybe the master cylinder) - the whole system was flushed and contained only DOT 5 when it was ready for use.

The two highlights is that (I think) it has a higher boiling temp (good for racing - not so much of a need on a station wagon [though it was heavy]) and it is not ?hydro-scopic? which means "attracts water".

It's the issue of not attracting water and thus a reduction of having rust form in the wheel cylinder walls / pistons and having a smoothly operating brake system was my goal.

Yes, it can't be mixed with DOT 3 / 4 (at least not when I had the car in the 80's/90's) and the fluid came with a large "STOP" sticker to be placed near the master cylinder so that DOT 3/4 would not be added on a top-off.

Not damaging paint was a plus, but not an important one. There was one time I spilled a bit on the fender so I simply wiped it all over the fender top - it made the old, flat, weathered paint shine nicely - and never damaged it.

I sold the car and never had any wheel cyl issues - but perhaps I didn't have it long enough that I'd have issues anyway.

[carpenle]

I have used dot 5 on motorcycles.