Whatever it is that anti-freeze does, it will almost immediately ruin the bearings in an engine. I have experienced this first hand. Thats why whenever I fire a new engine for the first time, I use straight water as the coolant, untill I'm sure that the cooling system is not leaking into the oil pan. It is a good idea to run anti-freeze all year round, because it has rust inhibitors to prevent rust build-up in the block and heads, and it has additives in it that help to prolong the life of the waterpump seals.----however, it should be changed once a year.