Synthetic brake fluid should be avoided by all who have non-synthetic brake fluid in their brake systems. It is incompatible with non-synthetic fluid, so a complete flush of the system (meaning every last drop of the fluid) must be done before the synthetic fluid can be added. Moreover, the synthetic fluid will not lubricate the rubber seals like non-synthetic, so a replacement of those seals may also be needed.

Considering that there are very good brands of non-synthetic brake fluid readily available for about $10/qt. it does not seem cost effective to switch to synthetic. YMMV.

~ Merry motoring ~

Ed Ruiz

=============

At 11:30 PM 2/9/02, MCLoveall@aol.com wrote:
>Wally:
>Thank you for clarifying that. I was getting worried. I've used the Motool DOT 5.1 synthetic brake fluid in Japanese and American cars for a years now with complete compatibility. From Ed's comments, I was beginning to suspect the 928's systems were somehow more fragile than its international counterparts. (whew!)

Perhaps more investigation is in order - DOT 5 fluid usually IS silicone.
The Valvoline synthetic and the ATE are both DOT 4 fluids. I am not familiar with the Motool (Mutol?) fluid, so can't comment.

Wally Plumley
928 Specialists

==================

At 08:59 PM 2/9/02, Ed Ruiz wrote:
>Synthetic brake fluid should be avoided by all who have non-synthetic brake fluid in their brake systems. It is incompatible with non-synthetic fluid, so a complete flush of the system (meaning every last drop of the fluid) must be done before the synthetic fluid can be added. Moreover, the synthetic fluid will not lubricate the rubber seals like non-synthetic, so a replacement of those seals may also be needed.
>
>Considering that there are very good brands of non-synthetic brake fluid readily available for about $10/qt. it does not seem cost effective to switch to synthetic. YMMV.

As Luke said, what we have here is a failure to communicate.

Synthetic brake fluid is not silicone brake fluid.

From Valvoline:

High Performance Synthetic Brake Fluid

Recommended for all ABS, hydraulic drum and disc braking systems and hydraulic clutches requiring DOT 3 and DOT 4 fluids. Its premium, synthetic, low moisture formulation provides superior anti-vapor lock protection. SynPower High Performance Brake Fluid has a high dry-boiling point of 513F that reduces the risk of fluid vaporization and possible brake failure. Wet boiling point is 333F. Meets and exceed  specifications SAE J1703, FMVSS No. 116. Surpasses Federal Motor Vehicle DOT 4 requirements. Mixes with conventional brake fluids.

The Valvoline synthetic is just standard brake fluid where the chemists have modified the glycol molecules to get a little higher wet and dry boiling points - I suspect that the ATE wizards did the same thing with their fluid.

No problem with using synthetic brake fluid. I agree with Ed that you should NOT use silicone fluid in the 928.

Wally Plumley
928 Specialists

=================

I faxed ATE in Germany last year asking them which fluid they recommend for my 89 S4.

Their response was:

Good-DOT 4 SL-Change every year

Better-Super DOT 4-Change every 3 years

Best-Typ 200-Change every 3 years

They also sent me this breakdown of the wet & dry boiling point for their products:

TYPE-Dry/Wet (celcius)

DOT3-220/150
DOT SL (DOT 4)-265/170
Super DOT 4 (DOT 4)-260/180
Typ 200 (DOT 4)-280/200
Super Blue (DOT 4)-280/200

Type 200 & Super Blue have identical specifications save for the color.

I alternate between these when I flush as it helps ensure you remove all of the old fluid.

One other note, the Type SL is available in 1/4 & 1/2 liter cans for those of you who don't like to use previously opened containers.

PJM