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Antifreeze Buying Guide: Choosing the Right Coolant

Any vehicle with an internal combustion engine is equipped with a cooling system filled with antifreeze. This brightly colored liquid promotes better heat transfer than just water, and it prevents the internal cooling system parts from corroding and, most importantly, from freezing. At some point, every vehicle will either need the antifreeze topped up or the system drained and refilled. For that, you’ll need to find the right option among the different coolant types.


For a gallon of coolant, you can expect to pay less than $25, regardless of the type you need. But if you fill your cooling system with the wrong type, it can be much costlier. Check out the different types of engine coolant, how to pick the right one, and how long coolant should last.

The Types of Antifreeze

Each brand has its own lineup of antifreeze or coolant products in the automotive market. Generally, there are three coolant chemistries that each will fit into. They include:

  • IAT coolant. Your conventional, green coolant that many DIYers are familiar with is known as an Inorganic Additive Technology, or IAT coolant. The base fluid is ethylene glycol, containing corrosion inhibitors that are considered not organic, such as silicates. 

  • OAT coolant. No, there aren’t any cereals involved in OAT coolant. It stands for Organic Acid Technology, and, as the name states, it uses organic acids instead of traditional inorganic inhibitors to resist corrosion. It has a longer service life and is more environmentally friendly. 
  • HOAT coolant. Hybrid Organic Acid Technology, or HOAT coolants, combines the best aspects of both conventional and long-life OAT coolants. It provides the best protection against corrosion and overheating and can be used in a wide range of vehicles, especially those that use aluminum components.

Among HOAT coolants, there are some differences to consider too. There are phosphate-free, phosphated, and silicated options, and it’s all about differing inhibitor technology based on what each manufacturer recommends for their vehicles.

Choosing the Right Type of Antifreeze

What color of antifreeze should you choose? It seems like there’s a rainbow’s worth of options on the market for coolant, but each has its purpose. When choosing the right engine coolant for you, whether to top up the antifreeze during your car maintenance or flush and fill the radiator and cooling system, the type you choose matters.

If you add an incompatible coolant to your engine, there could be a chemical reaction that forms deposits or causes the coolant to gel and clog the system. It might not contain the best corrosion inhibitors for your engine, leading to rust and contamination. It can even lead to engine damage or cooling performance issues that are much longer lasting than just changing the coolant again.

Here’s a breakdown of the applications for the different coolant types:

  • IAT coolant – older vehicles across all makes and models, typically around 2001 and older. The common color of this coolant is green.

  • OAT coolant – General Motors, Saab, and Volkswagen vehicles. They’re usually orange but can also be dark green, red, pink, yellow, or purple, depending on the coolant brand.

  • HOAT coolant – Commonly yellow coolant, it’s intended for Ford, Chrysler, and many European brands.

  • Phosphate-free HOAT coolant – It’s used primarily by BMW, Volvo, Tesla, and MINI. The coolant color is typically turquoise. 

  • Phosphated HOAT coolant is a common coolant chosen by popular Asian brands like Toyota, Nissan, Honda, Hyundai, Kia, and Mazda. It’s often pink or blue in color. 

  • Silicated HOAT coolant – You’ll use this purple coolant for high-performance European models like Mercedes-Benz, Audi, Porsche, and some VW models.

Keep in mind that the color of the coolant is not important. The coolant selection must specify that it’s intended for your application to avoid compatibility problems.

Helpful Antifreeze Articles

How often Should You Replace Engine Coolant?

Replacing your engine coolant is an important maintenance task that should not be neglected. But how often should it be done? It depends on a few factors, but here’s a general guideline to help you keep your engine in top shape.

Most manufacturers recommend replacing engine coolant approximately every 100,000 miles or every five years, whichever comes first. Certain coolants report being good for up to 160,000 miles or five years. However, if you drive in harsh conditions, such as hot weather or heavy traffic, you may need to replace the coolant more frequently. Your best bet is to follow the interval recommended by the manufacturer and use the correct type for your vehicle.

It’s also important to keep an eye on the coolant level and appearance. If the coolant becomes dirty or discolored, it’s time to flush and refill the system. And if you notice a sweet, syrupy smell under the hood, this could be a sign of a coolant leak, and you should have it inspected immediately.

Replacing your engine coolant is a crucial aspect of maintaining the health of your vehicle. Don’t neglect it – it’s a relatively quick and inexpensive task that can save you from costly repairs down the road. So, keep an eye on the odometer, check your coolant regularly, and always follow the manufacturer’s recommendations for the best results.

Shop for engine coolant at AutoZone and any other parts, fluids, tools, and accessories you need to keep your vehicle in pristine condition. 

Frequently Asked Questions

What happens if I use the wrong type of engine coolant?

Using the wrong engine coolant can leave your engine vulnerable to corrosion, and it might have a chemical reaction with metals. That could cause a clog or floating debris to form. You could also have engine overheating issues.

Can I mix different types of engine coolant?

Certain ‘universal’ coolants can be used with multiple types of antifreeze. However, not all coolants are compatible. Ensure the coolant you use states that it’s compatible with your vehicle.

Can I use water as a substitute for engine coolant?

Water alone is not sufficient at protecting your engine. It should always be mixed 50-50 with antifreeze for the right properties to protect against overheating and corrosion.

How do I know when it’s time to replace my engine coolant?

Coolant has a replacement interval that’s determined by your car manufacturer. As well, if it’s dirty or excessively acidic, it should be replaced.

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