What Is The Difference Between HOAT Coolant and OAT Coolant?

There is no denying the fact that engine coolant, also commonly referred to as antifreeze, is important for your car’s maintenance. When researching this online you will come across many different types, brands, and colors. There’s likely a color variation for every color in the rainbow when it comes to the different antifreezes.

All this variety can make it confusing for those that are not familiar with engines and their parts and various upkeep requirements. You may, in fact, even be tempted to forget all about it until you can no longer ignore the flashing lights and sirens on your car’s dashboard. But don’t close this tab just yet!

Here we’ll cover a nice easy breakdown of what engine coolant is and what the differences are between the types of coolant including IAT, OAT and HOAT coolant. A coolant, to generalize, is what helps to keep your engine from overheating during the summer and freezing during the winter. It is your engine’s temperature regulator and will help to keep your engine from exploding. Coolant is clearly critical to your engine’s functions.

A Brief History And Explanation Of Car Coolants

Originally, before any coolants had ever been created, water was used in an attempt to keep engines cool. However, water expands when it ends up freezing at just 0°C (or 32°F) and then starts boiling at 100°C (or 212°F). Since car engines typically run somewhere between 90°C (or 195°F) to 105°C (or 225°F) on idle, that was not a realistic option to help keep the vehicle’s engine temperature down. We had to come up with a better solution.

The use of salts was briefly considered, but that was not an option due to the fact that it created corrosion problems for the metals inside the engine. Sometime in the 1920s, it was discovered that alcohols such as methanol, ethanol, and glycol would make the perfect antifreeze solution and have been used ever since.

Most mechanics would agree that in a moderate climate, a mix of 50% distilled water and 50% antifreeze is the optimal engine coolant. However, you can increase or decrease either one to bring the freezing or boiling point up or down depending on your current situation and weather conditions.

As an example, if you’re going to be hit with a freezing winter you may need to up the antifreeze and add less water. Maintaining more antifreeze than water in a harsh winter will ensure that the water does not freeze up in your engine.

What Exactly Is In A Coolant?

A coolant’s base ingredient is usually one out of two alcohols and those are either mono propylene glycol or mono ethylene glycol. Here is a little background information on these two alcohols:

Mono propylene glycol is a synthetic liquid alcohol that is tasteless, odorless, and devoid of any color. Besides being a main ingredient in some coolants, it is also used in a lot of different industrial products and is the safer of the two glycols. Many manufacturers label propylene glycol alcohol as nontoxic. You can find mono propylene glycol used in various food plants and restaurants.

It can even be found in foods like ice cream and salad dressings! They also use this type of alcohol in some E-cigarettes. It has a boiling point of 370°F, which is less than the mono ethylene glycol. It also has a higher freezing point which is around -74°F.

Mono ethylene glycol is the main alcohol used in coolants for automobiles. It is also naturally colorless, odorless, and has an extremely sweet taste unlike the mono propylene glycol. This one is extremely toxic if swallowed.

Its freezing point is around 8°F and it has a boiling point of just about 400°F. When you mix mono ethylene glycol with water, it helps to raise both the boiling and the freezing points. Due to its sweet taste and toxicity it should be kept closed when not in use a far away from children and pets at all times.

What Is An OAT Coolant Versus An IAT Coolant?

OAT stands for Organic Acid Technology. OAT coolants are typically orange, but sometimes blue, red, and dark green in color. OAT coolants don’t contain silicates or nitrites but rather other additives, like corrosion inhibitors, to help improve the overall performance of your engine. OAT coolants can typically last for up to 150,000 miles, which is about 5x longer than an IAT coolant. OAT Coolant is what new models use, so you will find that car manufacturers like GM, Volkswagen, Nissan, and Toyota use OAT antifreezes.

It’s important to know what IAT coolants are as you’ll need to use them if you’re working with an older car. IAT stands for Inorganic Additive Technology. IAT coolants were the first coolants created back in the 1920s. They are typically good to use in older cars and should be changed every 30,000 miles (or every 2 years) or so. The IAT coolants are typically a bright green and they contain silicates which are typically used to help prevent metals like copper, iron, and brass from rusting. This is the coolant used in domestic models that were built up until the mid-1990s.

What Is A HOAT Coolant?

HOAT stands for Hybrid Organic Additive Technology. Think of a HOAT antifreeze as the best of both worlds when it comes to coolants. These HOAT antifreezes are usually dyed a yellow color by the manufacturer and, simply put, is a mixture of an OAT and an IAT antifreeze coolant. Some car manufacturers didn’t like that the IAT was outdated and for older vehicles, while the OAT didn’t protect against rust as well as IAT, so they blended them together.

A HOAT antifreeze will have both silicates AND nitrite additives. Car manufacturers like Ford and Mercedes Benz generally use HOAT coolant brands in their cars. There are also some HOAT antifreezes that are a turquoise, pink, purple and blue color.

This does not mean that you can mix an IAT coolant and an OAT coolant together and, voila, you have a HOAT. No, a HOAT coolant would need to be manufactured and premixed and then bottled and sold. Do not try to make your own HOAT antifreeze. Not all IAT antifreeze and OAT antifreeze can be mixed together, so it’s definitely better left to the professionals to ensure it’s done correctly. Most HOAT antifreezes will be labeled with terms like Global, G-05, G-11, G-12, or something of that sort. Also, HOAT coolant is typically reserved for cars that were built from 2002 and later.

Bottled Coolants

Speaking of being bottled and sold, pretty much any coolant you purchase today whether it’s an OAT, IAT, or HOAT, will already come premixed and pre-diluted. This helps to ensure that the correct combination of ingredients is ready and only needs to be dumped into your engine (or radiator if you have an older car).

It’ll make it a lot harder to mess up if there’s no guess work or measuring required. Another important note to consider with the addition of new mixtures and other brands is that you don’t want to merely go by the colors mentioned. Don’t get hung up on the colors and let them confuse you. Always make sure to read the label so you can ensure you’re getting the correct one.

Coolant Degradation Is A Fact Of Your Vehicle’s Life

Either way, no matter which antifreeze your vehicle requires and uses, it’s important to remember that it will degrade as time goes forward. The reason for this is that the ethylene slowly breaks down as it’s exposed to more and more heat over time. As it degrades, the efficiency diminishes too. So, upkeep is necessary.

Not keeping your engine well-maintained is probably one of the worst mistakes a car owner can make. Poor coolant quality can lead to catastrophic and possibly irreversible damage to your engine. Usually, coolant should be changed every two to five years depending on your car usage and which coolant you have in your engine.

It is important to become familiar with your vehicle’s manual and to make sure that you follow its guidance as closely as possible. It should indicate how often to change your coolant, as well as which exact type of coolant or coolant mixture to use in your particular engine.

You should also glance at your coolant a couple of times throughout the year. The best times to do this would be right before it gets really cold in the winter and right before it gets really hot in the summer. These times are optimal because if your coolant smells burnt, looks milky, or feels gritty rather than slick and oily, you can have it flushed and changed before any extreme weather hits.

Sometimes it is as easy as just topping off the fluid but if it’s been a while or if you drive your vehicle a lot, it may be time to have the whole system flushed and cleaned out. Luckily, that’s not something that has to be done often but when you do it you should notice a huge improvement on your fuel efficiency. That will also extend the life of your engine, so you’ll be a lot happier with the vehicle’s longevity.