I run plain water with water wetter, and just a little splash of antifreeze - a pint, max - the only reason is so if it leaks you can smell it, but it's not any slicker than plain water if it comes out on the track.

Antifreeze is slicker than snot on the track, I've seen more than a few cars spin in their own coolant where if it were just water it would have ben saveable.

In my own experience, I lost my coolant under my front tires coming out of the diving turn at Lime Rock. Same formula as above. If it was water and antifreeze - it would have been ugly scary, as opposed to one pucker-factor-5 halfspin-catch-recover.

In the winter I store the car with antifreeze, but I won;t go out on track with it.