[bobcowan]

That could be a problem. When you mix the two, they clot. Not a good thing in a hydraulic system.

I keep hearing that seal material can be incompatible, too. But have never seen that companies sell different seals depending on the fluid used.

Ideally, you should completly disassemble the system and clean it out. Rebuild the MC's and all the calipers. Flush the heck out of the lines to prevent clots.