"Which coolant should I use for my car, green or red?" This question is out of date. In the recent years, the number of coolant types and colors have increased. Today, you can see not only green or red coolant but also orange, pink, yellow, even blue. Today's topics would be "Why so many colors?" "What color is the next?" "What color is engine coolant supposed be anyway?" Let's find out what is different among them.

Coolant in the engine does three jobs.

1. Maintaining proper temperature of the engine
2. Preventing itself from freezing
3. Protecting against corrosion

As long as enough coolant is in healthy engine, the first two jobs are being done forever. The job #3 "protecting against corrosion" is done by chemicals in the coolant, and they get consumed during the job.

There are three basic types of coolant today.

• IAT (Inorganic Additive Technology) - This coolant has been around for decades. They contain silicates that create a protective coating in the cooling system, even in rubber hoses.
• OAT (Organic Additive Technology) - This coolant works very differently from IAT. Aluminum and iron have oxide layer on the surface in the presence of moisture. OAT anneal this layer for protecting against further corrosion.
• HOAT (Hybrid Organic Additive Technology) - This coolant uses both IAT's and OAT's corrosion inhibitors.

Each one has been developing by car manufactures to meet their specification such as a warranty and a maintenance interval. Until 1994, most domestic manufacturers used IAT. In 1994, GM started using OAT. Chrysler started using HOAT in 2001. In 2002, Ford followed by adopting HOAT.

IAT is green. GM's OAT is pink. Chrysler's HOAT is orange, and Ford's HOAT is yellow.

Although there are 3 types of coolant, why are there so many colors of coolant? Raw coolant has no color at all. All manufactures add color to the coolant. They can dye their coolant any color they want! The reason they dye coolant different colors is they want to distinguish their coolant with other types of coolant.

What if you mix two or three different types of coolant? Nothing happens. It maintains heat, prevents itself from freezing. However, when they are mixed, corrosion inhibitors are also mixed, and you can't tell how long mixed inhibitors will be able to work.

So, don't mix. If you need to add, use the same type of coolant. In general, you can replace IAT with HOAT. You can't use OAT for older IAT using engines.

Lastly, it is the most important to keep filled in the cooling system. No matter how new coolant is, being low on coolant creates extremely corrosive spots in the system. This will cause a leak. Depending on where that happens, the engine will be seriously damaged. This basic maintenance leads you to great saving on automobiles.