the coolant actually raises the boiling point of water.

may expereiment sa chem class noon pag nilagyan mo ng asin yung tubig mas matagal sya magboil. Same principle with the coolant. It actuall y raises the boiling point of water above 100 deg C. (pero i'm not saying na lagyan mo asin yung radiator water mo hehe)

aside from that tama sila may anti corrosion properties yung coolant

Gamit ka distilled water kahit yung nabibili sa water refill stations tama yung sabi ni Rodyok... again what we learned in chemistry diba distilled water is a form of pure water walng dissolved substances in it

Tap water may have dissolved calcium salts and minerals kaya possible na may build up in the long run.