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Antifreeze Explained: What It Does And Why It's Needed

We take a look at the different types & colors of antifreeze, characteristics of each, what type your automaker uses, and why antifreeze must be mixed with water.

"Antifreeze" is a chemical, primarily consisting of ethylene glycol, which when mixed with water serves to lower the freezing point and raise the boiling point of the mixture. Traditionally, the combination of antifreeze and water is known as "coolant". As opposed to air-cooled vehicles which rely on fan-driven air blowing over engine components, water-cooled engines use a radiator, water pump, thermostat, heater core, hoses, and passageways within the engine.

Within this system, the coolant travels in a circular path driven by the water pump, through the engine where it removes heat generated by combustion, through the vehicle's heater core (supplies heat to the vehicle's interior), and through the radiator where its heat is shed to the outside air, to begin the cycle again.

Antifreeze Become Brown
Antifreeze that's become brown or rusty in color indicates inhibitors have broken down to the point where rust and scale buildup can no longer be controlled.

With nothing more than the right corrosion inhibitors added, water alone would cool an automotive engine just fine - until outside circumstances caused it to freeze or boil over. Antifreeze was developed to prevent those disasters, and it contains additives that prevent corrosion of metal components it comes in contact with. In this article, we'll take a look at the different types and colors of antifreeze on the market today, the characteristics of each, and why pure antifreeze should be mixed with water for maximum effectiveness.

Like any fluid that goes into a vehicle, antifreeze has a lifespan and it has a point at which it begins to degrade. But it's not the ethylene glycol itself that wears out, it's the corrosion inhibitor ingredients added to it which get consumed. These inhibitors prevent rust from forming on metal parts such as water pumps and engine blocks, and they get used up at various rates depending on chemical makeup. Antifreeze that's become brown or rusty in color indicates that the inhibitors have broken down to the point where the solution must be replaced. If you're interested in replacing your old antifreeze, you'll find our article on servicing your cooling system helpful.

Adding Water To Antifreeze

Full Strength
"Full-strength" or "Concentrated" antifreeze has not been pre-diluted with water, so you must do so before using it.
Prime 50/50
Antifreeze that's been pre-mixed with water will always state that fact on the label clearly.

Unless antifreeze containers state on their labels that they've already been pre-mixed 50/50 with water during the manufacturing process, you're getting "full strength" antifreeze and must dilute it with water yourself. Typically, full strength antifreeze provides more value when purchased - even after the cost of distilled water is factored in. If you prefer the convenience of not having to worry about mixing things accurately yourself, 50/50 mix is the way to go.

Distilled Water Is Always Best

Tap water and even filtered water are full of minerals such as calcium and magnesium which leave deposits inside the entire cooling system - particularly around parts of the engine that reach high temperatures. So no matter what type of antifreeze your vehicle requires, use only distilled water when formulating your mixture. Because distilled water has been boiled and re-condensed, mineral deposits and other impurities have been left behind. And since it's available at any supermarket or auto parts store, excuses for not using distilled water are limited.

Distilled Water

The Mix Maximizes The Freezing And Boiling Points

No matter which type or color your antifreeze is, it will transfer heat away most efficiently when blended with the proper amount of water - a mixture percentage based on the lowest temperatures typically seen in your climate. Most regions are best suited to a 50/50 water-antifreeze mixture which will provide protection from a low of -34°F to a high of 265°F. In addition, maintaining proper freeze point protection ensures corrosion inhibitors remain at intended levels.

Freezing Point of Water
This chart shows the range of temperatures at which antifreeze of various dilutions will freeze solid.
Boiling Point of Water
The boiling point of an antifreeze/water mixture increases as more antifreeze is added.

It's interesting to note that pure antifreeze alone will not perform the task of protecting your vehicle's cooling system much better than water would by itself. In fact, pure antifreeze will freeze at a temperature not much below where water does. In the coldest climates, the most effective mixture against freeze-up will consist of 60-70% antifreeze (with the rest being water) - not 100%.

The Health Of Your Entire Cooling System Suffers If The Coolant Level Is Low

Antifreeze is much more corrosive when it's in the form of hot, steaming vapors instead of a normal liquid state. When a cooling system is constantly low, these vapors fill the extra available space - creating an environment that's extremely corrosive to components inside the engine. In addition, metal components which become exposed because there's not enough antifreeze quickly form corrosion - something that transforms clean, effective coolant into sludgy, dirty coolant. And, of course, a cooling system cannot transfer heat properly when there isn't enough antifreeze to do it. The engineers who created your vehicle designed it to operate full of anti-freeze, so make sure it's checked and topped off regularly. (If you find yourself adding coolant frequently, have the system checked for leaks as soon as possible.)

Varieties Of Antifreeze Color That Exist

The color of antifreeze is generated completely by coloring dye, not as a direct result of any chemicals mixed during manufacturing. That said, different colors for antifreeze do exist. While specific colors agreed upon in the automotive industry do signify chemical makeup, variations still exist within each shade. The main antifreeze colors you'll run across are traditional green, extended-life yellow, and extended-life pink or orange. In more recent years, some Korean automakers have even been using blue dye antifreeze.

Varieties of Antifreeze

Whatever color and type of antifreeze your vehicle was equipped with from the factory, we strongly recommend that you strictly follow your vehicle manufacturer's recommendations when it comes to adding or replacing coolant. In other words, use only the recommended type or color, and never mix antifreeze types. Some recently developed antifreezes sold on the market claim to be universal for all vehicles, but we would avoid anything making such a claim.

Green Antifreeze

Green Antifreeze

For many decades, virtually all anti-freeze was dyed florescent green and made of ethylene glycol. This type of traditional antifreeze uses "Inorganic Acid Technology" (IAT) as a chemical basis, and usually contains silicate or phosphate additives to prevent corrosion of metal cooling system components.

In recent times, there has been a movement to replace ethylene glycol with propylene glycol, which is less harmful if ingested. (You may see propylene glycol-based antifreeze marketed as "pet safe" or "environmentally safe".) Because corrosion inhibitors in traditional green antifreeze break down sooner, its useful lifespan is shorter - usually rated at three years or 36,000 miles.

Orange & Pink Antifreeze - Organic Acid Technology (OAT) Type Coolants

Antifreezes died pink or orange have been around since 1996 and feature a newer class of corrosion-preventing inhibitors known as organic acids. They do not contain the silicates or phosphates found in abundance in traditional green American coolant.

Orange Antifreeze
Rusty Sludge

These Organic Acid Technology (OAT) type coolants were widely used in Europe before being introduced to the American market, and they typically have a longer service life of 5 years or 150,000 miles because these inhibitors last longer before breaking down. It's important to note that organic acid antifreezes should never be used on older vehicles that have traditional copper-and-brass radiators, only aluminum or plastic ones.

Variations of this coolant type are used by General Motors along with some European and Asian manufacturers (see chart further above). Recently, Honda and Toyota have also begun using extended-life OAT coolants, and some Toyotas are equipped with coolant that's dyed red. Because of past problems with DexCool developing a rusty sludge if coolant level was chronically low, these two Japanese manufacturers insist that DexCool antifreeze not be used in their cooling systems.

"DexCool" is the marketing name most often used for extended-life orange coolant developed by GM, which many companies sell.
VW, Audi, and other marques use variations of their own mix named "G-12" that's died pink.

General Motors DexCool and other similar coolants use organic inhibitors named sebacate and 2-EHA (2-ethylhexanoic acid) that are tailored for cast iron engine blocks which GM used in abundance. Although those organic acids used in DexCool are stable for the long term and can handle hard mineral water, they have been found to have a number of issues. 2-EHA doesn't become fully protective until thousands of miles have passed, and it can soften plastic which can cause gaskets to leak.

Volkswagen, Audi, and other VW-owned marques use variations of their own mix named "G-12" that's died pink.

Light Yellow Antifreeze - Hybrid Organic Acid Technology (HOAT) Type Coolants

Coolant typically dyed a very light yellow is known as "G-5". Developed by German corporation BASF and originally designated Glysantin G05, it gained popularity with European automakers as well as Chrysler and Ford after Mercedes-Benz began using it in 1984.

Yellow extended-life coolant originated with European carmakers in the 1980s and is most commonly sold as "Zerex".

Valvoline is currently licensed to use the BASF formulation, and their similar version that's approved by Mercedes and other vehicle makes is most commonly sold under the "Zerex" brand name.

While HOAT coolants typically mix an OAT with a traditional inhibitor such as silicates or phosphates, G05 is a low-silicate, phosphate-free formula blended with a benzoic acid inhibitor.

Mixing Coolant Types Together Can Be Harmful To Your System - Add Pure Water In An Emergency

Combining any of the above-referenced antifreezes together is not recommended. If you're in an emergency situation where coolant level is low because of a leak, you're far better off adding pure water than a different type of antifreeze. If you've mixed different colors accidently, have your entire cooling system flushed out professionally as soon as possible.

Flex-A-Chill Antifreeze
Driven CSP Antifreeze

At best, mixing types of antifreeze will cause the lifespan of the new mixture to degrade to that of the one with the shorter service interval. At worst, different corrosion inhibitors that were never designed to mix will work against each other - damaging your vehicle's cooling system in the process. For example, mixing green coolant with orange or pink antifreeze will cause the resultant mixture to gel into a thicker substance which doesn't flow as easily - clogging cooling system channels, radiators, and heater cores. Left uncorrected, the water pump will overheat and fail. If the engine itself becomes overheated, there's a chance that head gaskets may fail and cylinder heads may become warped.

Coolant Additives

Powerful, high-horsepower engines tend to run hotter than smaller engines. If an engine has been modified in any way to produce more power, it will likely operate at higher temperatures than its stock version. In both these scenarios, it's not uncommon for underhood temperatures to increase. For this type of performance, coolant additives contain agents that reduce air pockets that can create "hot spots". As a result, there's more complete coolant contact with all internal engine and radiator surfaces - resulting in a cooler running engine without heat transference being compromised.

Corrosion inhibitors contained within the additives also replace inhibitors lost naturally over time - fortifying your system further against rust and sludge buildup. CARiD offers a full variety of antifreeze and antifreeze additives to keep your vehicle's cooling system healthy and running at peak performance. To help guide you through our choices, once you've entered the year, make, and model of your vehicle, you will be shown the antifreeze products compatible with your manufacturer's recommendations.

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