Getting ready to put the rear discs on... I figured I'd flush the system. Does anyone use silicon fluid in their car, and if so, is it worth it? I know that I have to get the old Dot 3 completely out to finish it all up, but all I want to know is is there a difference in pedal feel and performance.

 

I've heard that silicon brake fluid attracts moisture and needs to be bled much more ofted. The main reason for getting silicon is its high boiling point in racing applications. I don't think any fluid will affect pedal feel.

 

Nah... Dot 3 attracts moisture. Dot 3 is hygroscopic and actually absorbs moisture. That's why brake components rust from the inside out. I just keep hearing that the pedal feel is different.

 

Here are some pro's and cons of Dot 5.
DOT5 brake fluid is also known as "silicone" brake fluid.

Advantages:
DOT5 doesn't eat paint.
DOT5 does not absorb water and may be useful where water absorption is a problem.
DOT5 is compatible with all rubber formulations. (See more on this under disadvantages, below.)

Disadvantages:
DOT5 does NOT mix with DOT3 or DOT4. Most reported problems with DOT5 are probably due to some degree of mixing with other fluid types. The best way to convert to DOT5 is to totally rebuild the hydraulic system.
Reports of DOT5 causing premature failure of rubber brake parts were more common with early DOT5 formulations. This is thought to be due to improper addition of swelling agents and has been fixed in recent formulations.
Since DOT5 does not absorb water, any moisture in the hydraulic system will "puddle" in one place. This can cause localized corrosion in the hydraulics.
Careful bleeding is required to get all of the air out of the system. Small bubbles can form in the fluid that will form large bubbles over time. It may be necessary to do a series of bleeds.
DOT5 is slightly compressible (giving a very slightly soft pedal), and has a lower boiling point than DOT4.
DOT5 is about twice as expensive as DOT4 fluid. It is also difficult to find, generally only available at selected auto parts stores.

I personally wouldn't waste my time with the stuff unless I had a true ***** out road race car. It's way too much trouble to replace a whole hydraulic system to use higher boiling brake fluid. Plus the stuff eats seals fast and causes pooling.