It is anti freeze in it's purest form. Tompoole is correct though, at -3 or 4 you need 10% and more if it gets colder to prevent freezing.
So a 250 litre tank need's 25 litres, at a cost of approx £5 per litre, it is not viable to use.
If yo do traditional cleaning then it works very well in a bucket and does stop any freeze up, even on the coldest of days.
Did you know the Ice road truckers use it in their window wash system? True, I heard them talk about it.