(PHOTO: GETTY IMAGES)
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Remember the old days when antifreeze was antifreeze? No matter which brand you chose, the color was green and the formula
was glycol-based and contained silicates as corrosion inhibitors. You mixed the antifreeze 50/50 with water and poured it
in the radiator. As the engine operated, the antifreeze would perform its primary duties of carrying heat to the radiator,
preventing freezing (hence the name) and protecting against corrosion in the cooling system. Simply change the antifreeze
at the prescribed service interval and life was simple.
Confusion Abounds
Today, with four types of antifreeze technology and a rainbow of sometimes conflicting colors, there is a lot of confusion
among automotive people and consumers alike as to what color antifreeze is best for each vehicle. The easy part is that most
antifreeze is still made with ethylene glycol (EG), a type of alcohol made from ethane, while some environmentally friendly
versions are made with non-toxic propylene glycol (PG), a similar compound made from propane.
Inorganic Acid Technology (IAT) is the chemical composition for the traditional green antifreeze. IAT can be used with either
EG or PG and is most always fortified with silicate or phosphate additives that make it compatible with various metal cooling
system components. The generally recommend replacement interval is three years or 36,000 miles. 
Coolant varieties abound today. (PETE MEIER)
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Organic Acid Technology (OAT) was the first long life coolant (LLC)/extended life coolant (ELC) introduced in North America
and was commonly known in GM parlance as Dex-Cool. OAT antifreeze was widely used in Europe before its introduction in North
America. OAT is almost always EG. Its first dye colors were the orange and red color still used by General Motors. Green,
pink and blue have been added to the list of available OAT antifreezes.
In addition to its use in 1996 model year and newer GM cars and trucks, OAT also is used in 1996 to 2001 Audi, Land Rover,
Nissan, Mazda, Toyota, Honda, Kia, VW, Jaguar, Saab and Porsche vehicles. The generally recommend replacement interval is
five years or 150,000 miles.
Hybrid Organic Acid Technology (HOAT) is a combination of IAT and OAT with nitrites added. Manufacturers often refer to this
antifreeze as global, and will indicate on the bottle that it meets or exceeds the specification G-05 for most vehicles newer
than 2002, specifically Mercedes, Volvo, Ford, VW, Audi, Chrysler, BMW and Saab, and specification G-11 or G-12 for Volkswagen
and Audi.
As for color, Daimler/Chrysler's version is orange and contains 10 percent recycled antifreeze. Ford Motor Company's version
is yellow and does not contain any recycled antifreeze. The generally recommend replacement interval is five years or 150,000
miles.
It is interesting to note, however, that studies show 80 percent of glycol products produced in the U.S. are not recycled,
but leaked out of the vehicle. This would lead one to believe that many cooling systems are being topped off.
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Nitrated Organic Acid Technology (NOAT) is an OAT with nitrates added. This makes NOAT also suitable for use in heavy-duty
engine cooling systems. NOAT and HOAT are very similar in performance characteristics. Currently, only Heavy Duty vehicle
manufacturers are using NOAT. The generally recommend replacement interval is five years or 150,000 miles.
