What is Antifreeze?

What is Antifreeze?

Antifreeze, or engine coolant, is a colored liquid mixed with water that helps condition your engine in extreme temperatures. As the outside temperature changes from hot to cold, coolant is pumped throughout the engine block to maintain an even operating temperature. However, antifreeze does more than just regulate temperature. Maintaining proper fluid levels also helps prevent corrosion.

How does engine coolant work?

The word "antifreeze" can easily be interpreted to mean that the purpose of the fluid is to keep the radiator/engine from freezing. But those familiar with these fluids know that its main purpose is to keep the engine from overheating (to remove excess heat). The fluid does this by absorbing the heat of combustion and transferring it to the radiator, where it is dissipated through the cooling fins into the surrounding air. Engine cooling antifreeze is usually mixed 50/50 with water and poured into the engine's appropriate reservoir. The chemical glycol is used as a base to create a fluid that is pumped through your car's engine to regulate and maintain an optimal operating temperature in extremely hot or cold weather conditions.

While the water and glycol mixture provides engine cooling and provides freeze and boil protection, the coolant and the environment in which it operates presents other issues that must be addressed. These problems mainly include corrosion, scaling, deposits and aeration/foaming. The different additive chemistries needed to address these and other issues, as well as automaker specifications, produce variations in the color of coolants available in the market.

Colors often indicate differences in coolant chemistry and their suitability for various car makes and model years. Recommended coolant types vary by vehicle manufacturer, as indicated in the PQIA Quick Reference Guide. Importantly, however, while colors are often associated with coolant types, there is no industry standard that defines the color of each type. Therefore, although the color is a good indicator, the actual application still needs to refer to the instructions on the label of the antifreeze bottle.

Coolant Additives and Colors

Coolant comes in contact with a variety of metals in the engine and its cooling system. These metals include iron, aluminum, copper, lead and other materials that corrode when they come in contact with water and other chemicals in the cooling system. Therefore, coolants contain inhibitors that help protect engine and cooling system components from corrosion. In addition, coolants contain chemicals to reduce foaming tendencies, prevent oxidation, balance pH levels, and because glycol is toxic, European and related international certifications require the addition of bittering agents to coolants as an aversion agent to discourage human consumption by imparting a bitter taste.

Coolants also contain dyes that give them a unique color. Dyes provide visual cues to help users identify the product as a coolant and distinguish between the various types (chemical compositions) of fluids on the market. First, and most importantly, vehicle manufacturers specify the type of coolant for the make and model year they produce, and there are significant differences between vehicle manufacturers. Second, using a coolant other than the manufacturer's recommended type may affect the performance and life of the engine and cooling system. In addition, it may void new vehicle warranties. So regardless of the color of the coolant, it's important to read the label on the product to make sure it meets the vehicle manufacturer's recommendations. But with that said, coolant color does have value.

Vehicle makes and models require a specific type of coolant, and the color helps identify the fluid type. For example, fluorescent green is a color commonly used to identify products that use Inorganic Acid Technology (IAT), often referred to as "conventional coolant". This type was specified for most Ford vehicles built before 2003. After that year, Ford specified the use of Hybrid Organic Acid Technology (HOAT). This type of fluid, usually yellow in color, was also specified for most Asian-built vehicles prior to 1996. However, unlike many other automakers, most Asian vehicles switched from HOAT to phosphoric organic acid technology (POAT) in 1996.

Coolants are more than just anti-freeze protection, and there are good reasons for the color and price differences that appear in the marketplace. In addition to those related to color, consumers should also look for other important differences in coolants. For example, some are ready-to-use pre-diluted (a 50/50 mixture of water and glycol), while others are concentrates that consumers must mix with water before use. There are also differences in the service life of coolants. For example, some are designed to last longer (i.e., 150,000 miles).

IAT (Inorganic Acid Technology) Traditional or conventional green antifreezes are usually glycol based with silicate and phosphate additives to prevent rust and corrosion of copper, brass, cast iron and aluminum parts. For over 70 years, most U.S. original equipment manufacturers (OEMs) have recommended traditional green antifreeze.

HOAT (Hybrid Organic Acid Technology) OAT and IAT antifreeze mixture. Like IAT, it also contains silicate for aluminum protection. This type of antifreeze is generally sold worldwide and provides longer protection than IAT antifreeze and is free of nitrites, phosphates and amine chemicals.

DEX-COOL® is an OAT, a glycol based antifreeze free of nitrites, borates, phosphates, nitrates, amines and silicates with the same metal wear as IAT antifreeze Protect. DEX-COOL® is a trademark of General Motors.

SHOAT (Silicate Enhanced Hybrid Organic Acid Technology) long-life coolant capable of five years or 150,000 miles of antifreeze service life.

OAT (Organic Acid Technology) propylene glycol based antifreeze, without silicates, has the same metal wear protection as IAT antifreeze. Propylene glycol is less toxic, safer for the environment, provides longer protection than ethylene glycol, and is free of borates, nitrites, nitrates, phosphates, silicates, and amine chemicals.

SOAT (Silicate Enhanced Organic Acid Technology) long-life coolant is capable of providing five years or 150,000 miles of antifreeze service life.

POAT (Phosphate Organic Acid Technology) long-life coolant is capable of providing a seven-year or 250,000-mile freeze protection service life.

The above quick reference guide is intended to help consumers understand the differences in coolant types and their applications. Before buying coolant, be sure to check your vehicle manual to ensure the type of antifreeze recommended by the vehicle manufacturer and read the label, model and description on the antifreeze tank to help you make a better choice.

How often does my car need new coolant?

All lubricants required for your vehicle should be changed at various intervals to be effective. The same goes for your coolant.

You should have your coolant checked or replenished at least once a month, especially before hot summers and cold winters. For more precise information on when to clean and change the coolant in your vehicle, consult your vehicle's owner's manual.