Let it stay at -30 or colder for a while, and the blocks will crack with a non-optimal mix of coolant and water. I have seen more than one block crack due to incorrect coolant mix. There is nothing that can prevent water from freezing, the question becomes at what point. The whole idea of coolant is to drop the freezing point, and raise the boiling point of water to someplace that the car will never see. Same reason that cooling systems are pressurized (this is more for overheating). Its all related to what the conditions the car will have to work in. In some places, maybe freezing isn't an issue; most of them will have overheating issues in the summer. Up here, it can drop to -32C (not far from -26F) for weeks on end. if your coolant/anti-freeze mix is off, so that the freezing point of the coolant is not low enough, you will crack a block. It may not happen the first day, but it will happen; its not a question of if, but when. Considering that the cost is a couple of bottles of coolant and a couple of bottles of distilled water, it seems to be a bad place to try and save money.