It's a 70/30% ratio here in the scorching desert
If you're talking 30% antifreeze for economy, a stronger solution actually increases boiling temperature as well as reducing freeze temp. IIRC, a 60% glycol solution gives the lowest freeze point, As Jerry said, even stronger solutions start increasing freeze (or slush) point. Those poor souls in Fairbanks have to use freeze plug heaters overnight to be able to crank them over. I've heard stories of people driving away from their tire treads when they froze to the ground. I've experienced the square tire symptom, but never lost tires to the cold.
