Color-Coded Confusion

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."


The two longer-life coolants—OAT and HOAT—are able to improve on traditional coolants by reducing downtime and potential environmental concerns that come with the disposal of this highly toxic substance. But at the same time, they are more expensive than a conventional coolant, and some fleets see them as an unnecessary switch from green.

Penray doesn't manufacture coolants, but the company provides this crucial inhibitor package. According to Joel Gresmer, Penray's national sales manager, power fleet division, certain additive packages, such as OATs, are perhaps not always given the proper emphasis by OEMs. "One of the premises that some of the OEMs and the manufacturers of extended life coolants have put forward is that you really don't need filtration, and you don't need additives back in the coolant until you've reached between 300,000 and 500,000 miles," he says. "We contend that that is not a proper maintenance program."

"It's not that they're recommending improper maintenance," he emphasizes. It's simply a matter of Penray's recommendation that an extended life coolant not be ignored: "We feel that cooling systems need to be maintained and tested throughout the program."


If testing is critical, where should a fleet start? Chevron's Pellet explains the dangers confronting big fleets: "There's a lot of confusion out there. For example, we have some customers that lease their equipment. Their trucks do not always come back to their shops and so things get out of their control. This includes maintaining the cooling system and the cooling system chemistries," he says.

"What we have found—and these numbers are rough—is that a quarter of a fleet may have coolant that has been over-diluted. Over-dilution with water is an easy situation to detect and correct. We recommend checking the coolant at every PM with a refractometer. A glycol-based refractometer can easily, in a ten second test, tell you if you have the glycol you think you should have," Pellet says. "And if you don't, we recommend that you correct your freeze point—there are freeze point charts on the back of every coolant or coolant concentrate that will help you make this correction."

But if your coolant has been topped off with another formula, the stakes are a little higher. This is where regular maintenance and tracking comes in, especially if there is a possibility where you think an extended life has been topped up with a conventional coolant. "You think everything is fine, but if you don't have extended life technology anymore and it's mostly conventional, you may not be adding the SCAs (supplemental coolant additives) that you should be, and you could be getting into trouble," he says. Conventional technologies require routine SCA addition to replenish depleted inhibitor, such as nitrite for cylinder liner protection. Extended life coolants, however, do not require SCA addition. "If you are not sure whether you have conventional or extended life coolant, we recommend that you test your coolant for nitrite. Be sure that your have adequate nitrite for cylinder liner protection," Pellet says.


One of the most critical components to a cooling system is its water pump. According to Carey Norris, technical services specialist, ASC Industries, there are several ways to damage a pump, one of which is by not adhering to a manufacturer's recommendations:

"Maintaining the system so that it can pressurize properly—assuring proper coolant level, radiator cap and thermostat are functioning as intended—as well as maintaining the chemistry of coolant, will fully protect the water pump," Norris says. "Ignoring the manufacturer's service intervals risks the depletion of the additives, which will promote excessive corrosion."

Luckily, he adds, "Each type of coolant, whether IAT, OAT, or HOAT, will provide a good environment for the pump when the manufacturer's intended chemistry is maintained to their specifications."


It is also critical that a fleet have a good understanding of what conventional wisdom concerning coolants should be adhered to, and what falls into the 'myth' category.

Fleet technician Jackson describes some of the buzz around the shop: "If you're using a silicate phosphate and you put it in other types, there's a popular rumor that it will turn into jelly."

Pellet responds, citing the differences between the inorganic and organic technologies. "Conventional coolants contain things like sodium silicate and sodium phosphate—these materials work by forming a solid coating on the cooling system. They're designed to gel, but they're designed to do it in an orderly fashion. If the product gets too old—if it goes beyond its shelf life, if it has become overheated, gelation can occur," he explains.

"Having said that, organic additive chemistry, which does not contain any of these, will not and cannot gel, nor is it intended to," he says. "It protects in a totally different way. It reacts chemically with an area that needs protection, but it doesn't react with everything. More to the point, mixing organic additives with conventional inhibitors will not cause the conventional inhibitors to gel."


Another term that seems to get tossed around in the coolant arena is this idea of a "universal" antifreeze.

"Universal coolant was a term that was used early on as a coolant that could be used in any application, and it was probably true back in the 90's and before," Pellet says. "I don't think it is as applicable in this decade as it has been in the past. In order to be universal, you'd have to be able to meet the varying requirements of the different OEMs.

"If you have a set of specifications that say 'absolutely no silicate,' and then you have other specifications that say 'we demand silicate if you're going to get full protection for your engine,' you cannot have a coolant that meets both of these specifications, because they're contradictory. So in that sense, you really can't have a universal coolant," he says.

Penray's Gresmer concurs, citing the dual meaning of the term among suppliers. "It certainly is confusing. If you go to Ford or Chrysler or Mercedes-Benz and say 'we want to use universal antifreeze,' they will tell you that is the 2705 technology in yellow." This is in reference to a specific European technology for automotive and light truck applications that is a specific yellow color.

On the other hand, explains Gresmer, "If you go to Peak, or one of the many marketers out there of antifreeze, and say 'what does the word universal mean to you?' they'll say, 'that means our antifreeze can be used with every different type of antifreeze out there.' And that's hogwash; there is no such thing."


If your technicians are still confused, there are options. Chevron offers a website for training on all aspects of cooling system maintenance including frequently asked coolant questions,

"The course covers the various cooling system parts that need protection, how the coolant protects these parts, and how the end user maintains the parts the coolant is maintaining—how do you go about testing the coolant that's in there to find out if what's in there is good, and doing what you're hoping it's doing?" Pellet says.

Penray offers training as well in the way of two programs. "One is 'What Color is Your Coolant?'" Gresmer says. "We talk about all the coolants that are out there, and the effects that it has when you mix them."

Penray's other program offers fleets a chance to get their hands on a shop 'cheat sheet' for coolant-related questions. The 'Never Lose Your Cool' program offers a one-day in-house training seminar on all types of cooling solutions. "Each participant gets a laminated 'Solutions' card," explains Gresmer. "On that card, it's got all the different colors of coolants that are available, and a chart to say 'if your coolant is this color, here's the path you need to follow for checking, maintaining, and keeping your coolant current.'"

For more information, contact Gresmer at


If Penray's Aroyan can leave fleets with one piece of advice, it's this: "Look at the antifreeze spec', regardless of the color," he says. "The color is not going to be an issue, as long as the antifreeze meets the ESTM B6210 or the TMC RP 329A. If we look at the price of the engine, and the price of a truck, everything went up. Fuel pricing went up; insurance went up. You invest a lot of money in your truck, and you want to keep that truck running, so please: pay attention to the coolant."