Anti-Freeze, Non-Toxic, Propylene Glycol Formula that protects to -100º F burst. Ask for the best. Ask for the original Freeze Free. This industrial coolant and heat transfer fluid is the best on the market. Recommended for solar heating systems, home boilers, summer cottages, RVs, boats, trailers, cooling towers and more. Freeze Free will not adversely affect neoprene seals used in hydronic boilers. Freeze Free is a red liquid (easy to see if leaks occur) that is practically odorless . Freeze Free is a propylene glycol formula that contains a special corrosion inhibitor that provides the best anti-freeze and metal corrosion protection.