Anti-freeze facts

Posted on September 29th, 2015 by Rob Marshall


With colder weather on the way, our Technical Advisor provides ten little-known facts about car engine antifreeze.

1. Engine anti-freeze provides not only cold-weather protection but also a vital anti-corrosion role. While garages can test the strength of the anti-freezing properties, it cannot assess the anti-corrosion additives.

2. The vital anti-corrosion properties diminish over time. Therefore, the cooling system will need fluid changes between every 2-5 years, depending on the type of anti-freeze used.

3. Three main types of anti-freeze exist, IAT, OAT and a hybrid of the two, HOAT.

4. Using the wrong type of anti-freeze can cause engine damage. Be wary of topping-up a newer car with so-called “Universal Antifreeze”. GEM Motoring Assist has conducted research, suggesting that some universal antifreeze manufacturers’ claims might not be entirely true. Always top-up with a coolant that matches the type used in the system, especially for cars made in the last five years.

5. Raw anti-freeze is a straw yellow colour – it tends to be dyed to another colour during the manufacturing process.

6. There is no standardisation of anti-freeze colour – therefore, do not use the dye as an indication of the chemical composition.

7. Anti-freeze is not as effective as a heat transferring liquid, when used neat. A 50/50 mix with deionised water is recommended, for optimum cooling, anti-corrosion, anti-scale, anti-boiling and anti-freezing protection.

8. ‘Coolant’ is a term that can also describe an anti-freeze solution.

9. Anti-freeze is poisonous but children and animals are tempted to drink it, due to its sweet smell. Most companies add a bittering agent, to try and discourage ingestion. Anti-freeze can also be absorbed into the bloodstream through bare skin.

10. Due to its toxicity, consult your local authority, or the anti-freeze supplier’s data sheet, for advice on disposal. Alternatively, ask your local garage (or car dismantler) to add your unwanted anti-freeze to its recycling tank.