Protect your car's engine in the cold with the right antifreeze

Buying the right antifreeze is more than just matching the colour of your old coolant. You need antifreeze that's specially designed for your car’s engine.

Most antifreeze is actually antifreeze coolant, a mixture of traditional antifreeze and engine coolant. Car manufacturers usually design engines with a specific kind of antifreeze in mind, so check your car manual for the recommended antifreeze that’s best for your engine.

Inorganic Acid Technology (IAT): Most cars made between the 1920s and 1990s use IAT. This antifreeze contains silicates and phosphates that help prevent metal corrosion, making IAT antifreeze an effective radiator coolant. While naturally clear, IAT is dyed bright green for easy identification and should be flushed every 48,000 km.

Organic Acid Technology (OAT): GM, Volkswagen, Honda and Toyota cars all use OAT antifreeze. It doesn’t have corrosion inhibitors like IAT antifreeze, mostly because this antifreeze is used in engines with aluminium radiators, but it lasts much longer. OAT antifreeze ranges in colour from green to red and should be flushed every 240,000 km.

Hybrid Organic Acid Technology (HOAT): This antifreeze uses the same compounds as OAT antifreeze, so it lasts longer than IAT antifreeze, but it has added nitrates and silicates to help inhibit corrosion. Most Asian and European car manufacturers use HOAT antifreeze, as well as newer Chrysler vehicles. It’s usually yellow or orange and should be flushed every 240,000 km.

Never top up or mix antifreeze together. Instead, fully flush your antifreeze before using a new type. Your antifreeze should only ever be mixed with water to make it less viscous and more effective. The compounds in antifreeze are very sensitive, however, and can react with any extra chemicals in your water. Use distilled water for the best results. Never use HOAT or OAT antifreeze in older cars that originally used IAT antifreeze because they can damage the engine.

Consider these additional factors when buying antifreeze.

Propylene glycol or ethylene glycol: Antifreeze is either made of propylene glycol or ethylene glycol. Propylene glycol transfers heat less efficiently and more is needed to get lower freeze temperatures, but it’s more viscous and less toxic than ethylene glycol. Ethylene glycol is more efficient and found in lower-temperature antifreeze, but is highly toxic and can irritate skin.

Diesel or gas engine: Diesel engines require special antifreeze with supplemental coolant additives (SCA) to protect against cylinder wall corrosion. SCAs also help neutralize acids and can extend the life of your diesel engine.

Picking the right antifreeze comes down to your car’s manufacturer, engine type and weather. Always use antifreeze that’s rated well below your region’s coldest temperatures and never mix antifreezes together.