The Color of Antifreeze
Until recently, the color of the most commonly used antifreezes for both light duty
and heavy-duty engine cooling systems was predominately green. Its change
interval is normally about every two years or 30,000 miles (50,000 km) of use.
Then, long life (LLC) / extended life (ELC) coolant / antifreeze was introduced in
an effort to reduce maintenance costs, downtime and environmental disposal
costs and issues. With the introduction of this totally new concept, antifreeze
manufacturers wanted to differentiate this new product from existing antifreezes.
To accomplish this, they introduced different colored dyes for their LLC / ELC
products. Orange and red dyes were used first; now it appears there may be
virtually no limit to the different dye colors that may be used.
The purpose of this bulletin is to describe the dye colors currently available, the
chemical technologies being used and which vehicle manufacturers are using
which technology based on the information that is readily available at the time
this bulletin was published. The member companies of the FMC are confident
this issue is not static and new technologies and dye colors will continue to be
introduced in the future.
Antifreeze is used in cooling systems to both lower the freeze point of water and
raise its boiling point. It is also used as a carrier for different types of additives
such as sodium silicate to protect aluminum from corrosion, anti-foaming agents
and other corrosion inhibitors. Although straight antifreeze actually freezes and
boils quicker than tap water, when mixed with water in the proper proportions (a
50% / 50% mix is ideal) in a cooling system, it greatly increases the cooling
system's ability to perform its designed function of removing heat from critical
engine parts and to enhance the service life of the various cooling system
Inorganic Acid Technology (IAT) is the chemical composition for the traditional
antifreezes that are green in color. An IAT can be used with either ethylene glycol
(EG) or propylene glycol (PG). The normal IAT service life is two years or 30,000
miles (50,000 km).
Organic Acid Technology (OAT) was the first LLC / ELC introduced in North
America in 1994. OAT antifreeze had been widely used in Europe before its
introduction in North America. OAT can be either EG or PG but is mostly EG
based. Its first dye colors were orange and red. These dye colors are still used by
General Motors and Caterpillar. Green, pink and blue have been added to the list
of available OAT antifreezes. It is recommended that OAT not be mixed with any
other antifreeze technology. The normal OAT antifreeze service life is 5 years or
150,000 miles (250,000 km).
Hybrid Organic Acid Technology (HOAT) is a combination of IAT and OAT with
nitrites added. This makes HOAT suitable for use in both light duty and heavy
duty systems. Currently, two manufacturers are using HOAT for their vehicles.
Daimler/Chrysler's version is dyed orange and contains 10% recycled antifreeze.
Ford Motor Company’s version is dyed yellow and does not contain any recycled
antifreeze. Both of these HOAT antifreezes use the marketing designator of GO-
5. They are compatible with each other but mixing them with IAT or OAT is not
recommended. The normal HOAT antifreeze service life is 5 years or 150,000
miles (250,000 km).
Nitrated Organic Acid Technology (NOAT) is an OAT with nitrates added. This
makes NOAT also suitable for use in both light duty and heavy duty systems.
NOAT and HOAT are very similar in performance characteristics. Currently, no
OEM vehicle manufacturer is using NOAT. The normal NOAT service life is 5
years or 150,000 miles (250,000 km).
Since antifreeze is clear when it is manufactured, and water is clear, dye is used
to color the antifreeze for identification and marketing purposes. The color of
antifreeze is no longer an accurate indicator as to whether it is an IAT, OAT,
HOAT or NOAT formulation. Further, some antifreeze manufacturers market a
“universal” antifreeze they say is compatible with all OAT, HOAT and NOAT
formulations. These "universal" formulas are not for use with IAT and they will not
convert an IAT to an LLC/ELC antifreeze. Mixing IAT with OAT, HOAT or NOAT
antifreezes will not damage your vehicle’s cooling system; however the mixture
will negate the long life/extended life attributes of these formulations.
In conclusion, there are currently two oranges, two reds, green, dark green,
yellow, blue, blue-green, clear and pink dye colors available. With this variety of
dye colors and more to come, the service technician’s ability to properly service
and maintain light duty and heavy duty cooling systems properly will be greatly
challenged. It is imperative the technician be fully aware of what the vehicle
manufacturers' requirements for antifreeze are and those recommendations be
carefully followed. For further information regarding cooling system maintenance,
refer to TSB's 88-1R3, 89-1R2, 97-2 and 02-1.
For additional information, contact:
Filter Manufacturers Council
P.O. Box 13966
Research Triangle Park, NC 27709-3966
Phone: 919/406-8817 Fax: 919/406-1306
Administered by Motor & Equipment Manufacturers Association