Color-Coded Confusion

Don't be confused by color-coded coolants.

A fleet technician's worst anxiety dream might look something like this: swimming upstream in psychedelic rivers of orange, green, and purple coolant. Is it possible anymore to stock just one coolant, in one color, for your entire fleet? "So much information is available," says Larry Jackson. "Different shops and different people have different opinions about what we should be doing."

Jackson, an automotive technician for a government fleet in San Angelo, Texas, came to Fleet Maintenance echoing questions we had been hearing more and more lately. Jackson wrote, "It's probably a mistake to say (green) ethylene glycol is a universal by itself. A lot of people think that's true, but that doesn't make it a recommended coolant, so what do you do?

"That's the kind of urban legend-type rumor that is going around," he concluded, "and you might make a bad decision based on that."


It appears a bad decision on coolant is indeed bad. According to Sarkis Aroyan, sales manager for the international division of Penray, "Studies show that 40 percent of diesel engine downtime can be traced to the coolant. Really there are a lot of people out there who neglect the coolant."

If the statistics are that bad for heavy duty vehicles, think of what kind of neglect is going on with the light duty side of a fleet—especially when OEMs often sell vehicles stocked with their own proprietary formulas of coolant. Just how important is it to follow the OEM-recommended guidelines for coolant top-up and replacement? It is probably critical to first take a step back and try to understand exactly what type of coolant technology each of these different formulas contain.


There are three categories of coolants on the market. The first, and most traditional, is the classic green formula. This is sometimes referred to as IAT (Inorganic Acid Technology) or "conventional" coolant. The additive package in an IAT contains inorganic corrosion inhibitors such as silicates and phosphates.

The second type goes by the moniker OAT, an abbreviated reference to the basis of its additive package, Organic Additive Technology. An OAT coolant should last longer than a conventional, as the additive package is slower acting. In passenger car use estimates put the life of an OAT coolant at 150,000 miles or more, compared to the 30,000 mile estimate on an IAT coolant. For heavy duty applications some OAT coolants are good to 750,000 miles and beyond.

A third coolant, HOAT (Hybrid Organic Acid Technology) is similar to the OAT formula in that it contains organic additives for corrosion protection. The HOAT also contains silicates in its additive package, for aluminum protection. In automotive applications HOAT should last five years or 150,000 miles.


But just knowing this information is not enough. According to senior staff chemist for Chevron Global Lubricants, Dr. Regis Pellet, there are plenty of ways in which these formulas are confused. Often, conventional coolants are referred to as ethylene glycol, which is not incorrect, however, "saying 'traditional technology based on ethylene glycol' suggests that OAT is not based on ethylene glycol," he says. "That is not true. All of the products we're talking about are glycol-based or water glycol-based."

Just to get back to the basics, "Just about everybody is using the water glycol system today," Pellet explains. "It doesn't matter whether you're using traditional technology or extended life or hybrid—you're using a water glycol base. That's not where coolants differ; the way coolants differ is in the inhibitor package—the sodium phosphate or sodium silicate or organic carboxylates. Whether inhibitors be organic, inorganic, or whatever, they represent maybe five percent of the coolant. That's all. The rest of the coolant is water glycol. But that five percent really distinguishes from one technology to the next."


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