Picking the right color antifreeze will help you in your daily work.
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.
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.
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.Why All the Different Coolant Formulations?
A little history might help clarify the situation. In the early 1980s, Ford was working with antifreeze manufacturers to come up with globalized formulation that did not use silicates. European countries have very hard water, and because water is 50 percent of the antifreeze mix, water quality dramatically affects the overall combination. At the same time, European manufacturers were abandoning phosphate-based technology because phosphates tend to form scale, and Japanese manufacturers were moving away from silicates, which had a problem getting into water pump seals and destroying them.
The first waves of alternative coolants were hybrid types that combined carboxyl and silicate technologies. Ford started using them after extensive durability testing (more than 40 million fleet test miles on every vehicle platform Ford had) in the early 1980s. At about the same time, Mercedes and VW also were using hybrid type formulations.
As vehicles have become steadily globalized over the years, antifreeze technology has naturally followed. The big three in coolant manufacturers, Chevron/Texaco, Honeywell and Ashland, have responded to the manufacturer's requests for corrosion inhibitors that will best suit all the markets for which the manufacturer produces vehicles.
Do Coolants Break Down?
From a maintenance point of view, engine coolants do break down. For example, ethylene-glycol based products break down and form organic degradation products, which ultimately cause corrosion problems. In engine coolant, problems with corrosion are negated by using some type of buffering agent. Eventually coolant does have a finite life.
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 the conclusion that many cooling systems are being topped off. By adding fresh coolant into the system, you are in some ways effectively extending the life of the coolant.
Can You Mix Coolant Technologies?
There is only one universal coolant that all manufacturers can agree on, and that is water. The only problem is that water by itself needs a little help. Needless to say, there is a lot of misinformation out there about what happens when you mix coolants.
According to Dr. Paul Fritz, senior coolants technologist for ChevronTexaco Products Co., "A lot of the confusion stems from work that was done when carboxyl coolants were introduced. There was one particular American Society of Testing and Materials (ATSM) test that showed that when you mixed the IAT and OAT coolants it showed a higher level of corrosion."
Ultimately, it was shown that the particular test was creating a very corrosive environment because the conventional coolant was diluted so much that it became corrosive.
The best advice is to use the same type of coolant that was originally used in the vehicle.
"If you do not know what coolant is in the vehicle and you top-off with the brand of coolant you normally use, nothing bad is going to happen," Fritz advises.
Only when dilution rates border 50 percent is the effectiveness of each coolant's inhibitor package compromised.
"All coolants are over-designed when developed. Each coolant is tested using only 20 percent of the level of inhibitors to be used," says Fritz. However, when adding an IAT to an OAT, the recommended coolant change interval will degrade to that of the shorter-life coolant.
Proper Maintenance is the Key
As with anything automotive, proper maintenance is the key to longevity. More important than the type of antifreeze you use is to maintain the cooling system properly by maintaining freeze point protection and proper coolant level. Almost all coolants are formulated to work best at the ideal freeze point mixture, which for most parts of the country means a 50/50 antifreeze to water mixture.
At this level, antifreeze will provide protection to minus 34 degrees Fahrenheit and boil over protection to 257 degrees Fahrenheit. In addition, maintaining proper freeze point protection makes sure the corrosion inhibitors are present at the intended levels.
Cooling systems are designed to operate full of antifreeze. A system that is constantly low on coolant can create an extremely corrosive environment because of the aggressive nature of the vapors of a glycol/water mix. These steam vapors are more corrosive than either fluid by itself. For example, one technical bulletin warns that vehicles operated for 15,000 to 20,000 miles with low coolant levels "may be susceptible to the formation of a rust-like material in the cooling system."
A proper antifreeze level is also important after shutting off the engine. As the antifreeze stops flowing and the engine temperature increases dramatically, areas of localized boiling can send large shock waves through the engine, wreaking havoc on components, especially those made of aluminum.
In almost every part of the country, tap water contains minerals like magnesium and calcium that can form deposits in a cooling system, especially on the engine's hottest parts. This is why the water you use to mix the antifreeze is so critical.
Coolants that are sold premixed are mixed at the factory with distilled water, and distilled water, not tap or filtered water, should be used when you refill any cooling system.
Jim Marotta is a freelance writer with more than 17 years experience in the automotive industry. He currently works as a technical editor for ChiltonPRO.com.
