[Butcher]

Brine solutions are unlikely to be dielectric also.

FluidXP is mainly water FWIW, similar stuff to PC ICE.

I can't really see any alternatives to fluorinet (or similar), especially if you're concerned about leaks. Unless the system is in a very well ventilated area, a methanol leak is likely to be more than just an inconvenience - it could be life threatening.
Make no mistake about it, methanol is a dangerous toxic chemical and should not be used lightly. You can quite easily kill or blind yourself with methanol vapours if you have a couple of gallons of it kicking about.