Joe '87 S4

I got some DOT 3 non synthetic to top off. I'm going to flush it next week. It's due.

jheis

"Synthetic" is fine. It's silicon brake fluid (DOT 5) that you want to avoid.

I like Valvoline Synthetic. Its wet and dry boiling points are nearly as high as Ate fluid but it's cheap and readily available at any Pep Boys or other local auto parts emporium.

The most important thing is to flush your system every year (or two). Brake fluid is hygroscopic - meaning that it absorbs moisture. Fluids cannot be compressed - which is why hydraulic brake systems work - when you step on the brakes, the force on the pedal is transmitted directly to the brake caliper through the brake lines. However, if your brake fluid is old and has absorbed moisture, the moisture can "boil" under heavy usage and be transformed into a gas. Unlike a fluid, a gas can be readily compressed - causing loss of brakes - just when you need them the most!

James

Edit: I see Bilal has already recommended Valvoline Synthetic, so I'll second his recommendation.

Mrmerlin

I will say this again use the ATE super blue fluid,
flush out the old and then you should be good to go.
Roger sells the super blue fluid its about 14.00 a liter

Joe '87 S4

Good to know the synthetic is fine to use. I topped off for now but will get it flushed and new fluid put in this coming week. No good having a fast car if you can't stop! :-)

MGW-Fla

Interesting that on Tire Rack it says "NOTE TO FLORIDA RESIDENTS ONLY: ATE Super Blue Racing Brake Fluid, due to its blue color, cannot be registered in and is not DOT-approved for street cars in Florida." Only in Florida I guess huh??? I guess they'll have the brake fluid police checkin your fluids randomly!!

Gary Knox

I believe the ATE super blue (and maybe amber) are significantly more hygroscopic than the DOT 3 (and probably synthetic) brake fluids. I change the super blue twice a year in my track car for that reason, as the absorption of moisture significantly lowers the boiling point (had some vaporization at the Glen this past fall with ATE blue fluid that was less than 6 months from opening the can).

For my street car, I use the Castrol LM. I believe it to be much less hygroscopic and change every 3 years - never any sign of corrosion (I rebuilt my calipers last winter, first time in 15+ years of usage).

Gary

Speedtoys

This means you need to likely service brake pads.

Fluid goes down because pads wear..if you add more fluid, you'll get to then remove it when you (soon now) need to replace some pads.

depami

Cool! Dolby Digital Break Fluid!

Does that mean you not only hear them squeel at all four corners, but feel it too?

MGW-Fla

So Gary what would you recommend for my '85 that will see a few DE's and/or Autocrosses during the year and only driven a few days a month on the street? I was planning on switching it to the ATE 200 Amber?

z driver 88t

I thought this too, but I just checke ATEs website and they have a recommended change interval that INCREASES with increased boiling points. I.E. up to 3 years for the Super Blue and Amber 200, but 1 year on the regular DOT 3 and DOT 4 stuff.

http://www.ate-na.com/generator/www/...f_info_us.html

I'd be curious how you actually measure water content of brake fluid. It would be interesting to test by leaving a couple cups of different brake fluids exposed to atmospheric conditions for a few days or a week and test them.

Speedtoys

You measure it by seeing where it boils pretty much. It degrades incredibly fast if open to moisture...doesnt take much at all.

You have more water in your fuel right now, than you would ever accept in your brake fluid.

MGW-Fla

Sounds like a test for an Engineer eh Chris??

Speedtoys

http://www.vacc.com.au/ConsumerInfo/...4/Default.aspx
http://workshop.search-autoparts.com...152/31710.html

z driver 88t

Those are some excellent links and really useful information. It does seem to support the notion that the Super Blue is no more hygroscopic than other DOT4 fluid and that increased boiling point yields increased service life of the fluid.

Mel - funny - I forgot you knew I was an engineer - must have been talking with James Bowen. Actually it sounds like a great science fair project for one of my daughters in about 9 years.

MGW-Fla

I thought I'd remembered a while back he mentioned that's what you did. He & his wife were at our house on Christmas day since they're now my daughter's in-laws.