Freeze point for low tox & ww fluid

[rarmstrong]

Picked up some Prestone low tox today and going to mix it 50/50 with the cheap -20 varity windshield washer fluid to winterize the raw water side of my inboards. Previoulsy I've used the -100 stuff from the boat store. Has anyone tested the freeze point for this mix? I believe the Prestone jug gives a -26 rating using 50/50 plain water so the ww fluid should give it something better. Does this stuff slush at a higher temp like the pink stuff does?