Using DOT 4 fluid

[bacarl]

Hi everyone, I apologize in advance for this because I feel like this topic must have been beaten over and over, but I wasn't able to find anything via search (probably has to do with all the search terms being too short: DOT, 4, ATE, etc).

Is ATE Super Blue safe to use in stock 240Z brake systems or are there incompatibilities with the original, designed-for-DOT-3 components? Thanks much...

[LeonV]

DOT3 and DOT4 are compatible.

[conedodger]

I use Super Blue... No problem.

[Arne]

DOT 4 typically is a higher boiling point, but absorbs moisture from the atmosphere quicker. It is fine to use in cars calling for DOT 3, but you should change it more often than most people do. Most cars that use DOT 4 specifically have fluid flush intervals of 2 years or less.

[surfer.tech]

I use DOT4 as well.

[Zedyone_kenobi]

DOT 4 fluid for sure..

But if you are not going to occasionally track the car DOT 3 is perfect. Just get a good brand name and you are set.

also, invest in some speed bleeders.. you will thank me later.

[bacarl]

Thanks guys. I know about the higher boiling temp and the higher rate of water absorption, but my question comes from this thread which has the following info from Carroll Smith and James Walker:

DOT 4 fluids are also glycol ether based [like DOT 3 fluids], but have a measure of borate esters thrown in for improved properties including increased dry and wet boiling points.

...

As a trailing note on the DOT ratings, if your car was designed for a particular type of fluid (especially prior to the development of DOT 4 fluids), you should make every attempt to stick with that fluid! For example, if your car was delivered with DOT 3 fluid, the internal components of the system (seals, brake hoses, and fittings for example) were specifically designed and tested for compatibility with DOT 3. Because DOT 4 fluids contain a different chemical composition, the system may not necessarily react in a positive fashion to the borate esters floating around in the mix.

In other cases, just the difference in viscosity of the two different fluids may cause the seals to wear at different rates. What starts as an annoying squeak might eventually become a torn seal or worse. The examples could go on and on, but the message here is this: it’s fine to upgrade from DOT 3 fluid A to DOT 3 fluid B, but you should think twice (maybe even three times) before switching from DOT 3 fluid A to DOT 4 fluid of any sort.

I never like to "upgrade" to a not-factory-spec'd part or fluid without doing at least a little research first

Edited May 17, 2013 by bacarl

[siteunseen]

Plus me on those speed bleeders, fronts are different size than rear though. I put one on my slave cylinder too.

[Jeff G 78]

I always run Ate in my 260 race car. It works great for 24+ hour long endurance races. I always keep it fresh though and I rebleed after each race.