The only time I had a completely new and dry braking system, when I rebuilt my BV8, I thought long and hard about using silicon fluid.
In the end, there were just enough stories of sticking cylinders, and spongy feel to put me off.
Maybe on a dry fill it would have been OK. but it was never adopted by manufacturers so far as I know.
I've been using dot 5.1 in my Roadster, until the last replacement, which has similar performance properties to silicon, but is conventional brake fluid.
Last time I had some 4.0 to use up so that went in.
Well, you can all consider me as a guinea pig, having had silicone fluid for three years. I have not noticed any spongy feel, no significant difference compared to pre-silicone period. I might have if I were tracking my car, who knows. But being the cruiser I am, I experience just the same braking feel. As for sticking cylinders, one piston in each cylinder did stick. But as the cylinders most likely had been there since 2004, I believe the sticking was because of old age and visible rust, not the silicone fluid. Again I emphasize the importance of extremely thorough flushing of the system before filling up with silicone. No issues so far, but if anything turns up, I will report immediately
