What’s the Difference Between Engine Coolant and Antifreeze

Your vehicle’s coolant system ensures your engine starts up and keeps running despite high environmental and operating temperatures. It also ensures that your vehicle can turn on in extremely low temperatures. To keep this pivotal system in optimal condition, checking and changing your car fluids appropriately is important. 

When it comes to the fluids used in your cooling system, coolant and antifreeze are often used interchangeably, but they are not quite the same. Being able to discern the difference is important, especially if you are a DIY kind of person. Adding one to your engine will allow it to stay cool while operating in warm weather and keep it from freezing in cold weather, while the other is only a piece of the chemical formulation. Can you guess which is which?

• Coolant – What does coolant do? It is a combination of water and antifreeze meant to keep your car’s engine operating as it should despite the external and internal temperatures. This is usually a 50/50 ratio of water and antifreeze, but some mixtures could be as high as 70% water and 30% antifreeze in warmer states. If you purchase a bottle of coolant, it has been pre-mixed with antifreeze.
• Antifreeze – What does antifreeze do? This fluid is a “concentrated coolant” made up of ethylene glycol. Unlike coolant, which is pre-mixed, antifreeze is a concentrate meant to be mixed with water before being added to your vehicle. Adding antifreeze without water will hinder your vehicle’s ability to transfer heat and could lead to overheating, especially in warm weather. 

When to service your coolant system

When it is time for you to change your coolant, your vehicle will start to show signs. Some may be more obvious than others, so knowing the symptoms and being vigilant is important. Some common signs include:

• Your engine overheats.
• Steam flows steadily from under the hood.
• Your temperature gauge is running higher than usual.
• You smell a sweet syrup-like aroma under the hood of your vehicle.
• Your check engine light comes on.
• Rusty-looking coolant.

If you notice any of these symptoms, it may be time to change your vehicle’s coolant. 

Conventional vs long-life coolants

Now that there is a basic understanding of coolant and antifreeze and a good sense of the symptoms that could indicate an immediate need for a coolant change, the next thing to consider when maintaining your vehicle’s cooling system is whether to use conventional coolant or long-life coolants.

• Conventional coolant—Conventional coolants are made up of inorganic silicates that fight corrosion in the engine. However, over time, these silicates will build up and should be flushed out with a cooling system cleaning. This buildup is the primary reason why you should change conventional coolants roughly every 30,000 miles.
• Long-life coolants or extended-life coolants—Extended-life coolants use organic acid technology to provide enhanced corrosion protection and heat transfer, as well as greater longevity of life for your vehicle’s water pump while reducing overall maintenance costs. This organic technology, plus the protections it offers, allows you to go nearly 600,000 miles before it needs to be changed, provided an extender is added at 300,000 before the fluid needs a complete change. 

Advanced additive technologies

The lifespan and performance of your coolant largely depend on the additives it contains. Here is a breakdown of the primary technologies behind these additives and how they impact your vehicle.

• Inorganic Additive Technology (IAT) – Inorganic technology is the oldest type of coolant technology. It utilizes mineral-based additives like silicates, phosphates, borates and nitrites to protect the engine from corrosion. These inorganic materials create an insulation layer that protects metal parts from cooling fluid. Because of these inorganic components, fluids in this category must be changed out more often.
• Organic Additive Technology (OAT) – Organic additive technology is a bit newer and replaces the inorganic material with organic acids that are used to protect against corrosion. These acids are used in extended life coolants. Coolants made with this technology last significantly longer; however, their corrosion resistance is not as strong as their inorganic counterparts.
• Hybrid Organic Additive Technology (HOAT) – This hybrid technology utilizes a combination of organic acids and inorganic additives to protect the engine from corrosion. This is considered the best of the three options, as drivers will get the protective corrosion resistant properties of IAT and the longevity of OAT all wrapped into one powerful coolant.

You know the signs, you can tell the difference between coolant and antifreeze, and you have a small overview on the technologies present in the various fuel systems that are out there. 

But remember, just because something sounds like it could be good for your vehicle does not mean that it is. Be sure to consult your owner’s manual before performing any maintenance yourself. When in doubt, be sure to reach out to your local auto parts store, a trusted mechanic or AAA-owned Car Care Center or AAA Approved Auto Repair shop to make sure you are pointed in the right direction.