Hi Tony,
A correction here, DOT4 (as well as DOT 2 and 3) are not termed "mineral", they are a synthetic.
The systems that use a mineral fluid are Rolls Royce, Citroen, etc and certain military vehicles used by the British Army (and others!), which is a very low viscosity hydraulic oil.
I also understand that water can be absorbed into silicone fluid so not as good as we were led to believe. Also have to remember that although you might have cylinders sleeved with Stainless Steel, the pistons could still be a ferrous steel.
regards, Richard