Light Duty: Color By Numbers

Larry Jackson, a veteran U.S. Government fleet maintenance professional, has some problems with his coolants. “Our biggest issue is with our drivers, who don’t really care and aren’t paying attention,” he says. “They’re not educated about the differences (between coolants) and about the additives.

“Among our technicians, there’s confusion about why one type of coolant works better than another, and why we can’t consolidate to one coolant product,” he goes on. “It’s pretty clear the manufacturers are all using different additives in their coolants; do we need to know why?”

Jackson’s questions are all part of a bigger issue that we here at Fleet Maintenance hear about over and over again, year-in and year-out: Why are there so many different types of light-duty coolant products, and is it safe to use one universal product in every light-duty vehicle in the fleet, regardless of its make?

“This is a complex issue, because of the different recommendations and the different coolants,” says Stede Granger, OEM technical services manager, Shell Lubricants. “If you have a shop and you’re stocking multiple coolants in inventory, it’s much simpler to stock just one coolant, and also if you stock a different coolant for every vehicle then there’s always the chance that the wrong coolant will be put into the wrong vehicle.”


“When you look at municipalities, electrical contractors, people who run mixed fleets with heavy-duty and light-duty vehicles, they’re looking for a product that they can use in everything,” says Shawn Martinelli, southeast regional manager for Penray, Inc.

According to Martinelli, the old green automotive coolant has given way to two newer varieties: hybrid coolants and Dexcool-type extended-life coolants (ELC). Fleet managers looking to use only one product in all the fleet’s light-duty vehicles have to choose which one of these coolants best suits them.

Martinelli points out that all coolants are essentially 50 percent glycol and 50 percent water. The only real difference between coolants is the makeup of the corrosion inhibitor package.

“The ELC, the Dexcool-type product, works very well,” Martinelli says. “It’s good for five years or 150,000 miles. But you can’t contaminate it! The inhibitor package that they use consists of organic acids, and when you dilute that corrosion-inhibitor package, you lose that protection.

“That’s very hard for a fleet to manage, so more of them go with the hybrid product, which is a mixture of more of those technologies,” he explains. “You can contaminate it with another antifreeze and it won’t mess it up, and it will still go for five years and 150,000 miles. You can use it in all makes and all models; you can use it in any color. That’s the type that I would point a fleet to if they were all-automotive and they wanted to go to one coolant. It’s the one-size-fits-all solution.

“Of course,” he says, “we have to add the disclaimer, ‘Always check with your engine manufacturer.’”


Fred Alverson, advisor for Shell Lubricants, clarifies the choices fleets must make:

“For fleets that do have various types of vehicles, there are universal types of coolants out there that could be used if they want to simplify their monitoring and maintenance programs,” he says. “These universal coolants that make the claim that they’re safe for all makes, all models, all years of passenger cars, they will not meet the OEMs’ chemistry requirements, but they have been carefully formulated to meet the performance requirements in a wide variety of engines.

“Shell’s position is, we always follow the OEM’s recommendations,” he says, “but for those fleet managers who want to simplify and go to one coolant, we recommend they contact their coolant supplier, such as Shell, and we’ll look over their vehicles and if a multi-vehicle is suitable, we would recommend it. And then with our multi-vehicle product, we have recommendations that they should follow on the application and use of the product, along with mixing this product with other coolants.”


But, if it’s possible to cover all makes and models with one universal coolant product, why do OEMs all recommend different products?

“The OEMs design their cooling systems differently, with a wide variety of metals, so the OEMs specify coolants and corrosion inhibitors that they feel provide the best corrosion protection performance in their engines,” Alverson explains. “So, certain OEMs favor silicated coolants because of their excellent protection of aluminum, while other OEMs achieve satisfactory corrosion protection using other coolant inhibitors without silicate, such as phosphate.”

With hybrid coolant technology, Alverson says, you benefit from the long-life feature, and you get the targeted protection from the silicate for a specific metal.

“Also,” he says, “silicate provides faster initial passivation; it goes right to the metal surface, while the organic inhibitors take a little longer to passivate the metal surface. Fleet managers not using hybrid organic additive technology coolants in vehicles designed for these coolants may not obtain the optimum corrosion protection.”

According to Alverson, regardless of what coolant you use, a good, sound coolant monitoring and maintenance program is the best method to achieve maximum coolant life:

  • The coolant system should be inspected for coolant level, and should be topped off, at each PM;
  • Coolant should be checked twice a year for freezing point, preferably using a refractometer, or, alternatively, a hydrometer or test strips;
  • A refractometer is a low-cost piece of equipment—less than $200. It’s durable enough for shop use and provides as accurate a reading for coolant concentration and freeze point as does the laboratory;
  • Coolant should be adjusted with good quality water to maintain 50/50 dilution, to help maintain the OAT corrosion inhibitor level.


That last point bears a closer look. Coolant, of course, does not work alone, but Brad Drake, technical writer for Wix Filtration, fears that technicians often overlook coolant’s silent partner: water.

“Starting with good water—distilled, deionized—is critical, because it’s at least half of the mix,” Drake explains.

The additive package that exists within any coolant has a lot of different jobs: it protects against corrosion and oxydation, and it neutralizes PH. The optimum PH level in a coolant system is between 8.5 and 11, but if a technician introduces water with very low or very high PH, or introduces hard water, the coolant has to immediately go to work to neutralize those elements in the water. In other words, you’re using up your additives before the vehicle has even left the garage.

Drake explains that light duty coolant contains a lot of sodium metasilicate, and hard water in particular can cause silicate dropout: “The sodium metasilicate does not blend well with coolant, so it doesn’t do a good job staying in suspension as it is,” he says. “And when you blend it with hard water it drives those two chemicals a little bit further apart, and what happens is the silicate will drop out of suspension and form big globs that have the potential to clog coolant passages and generally make a mess of things.

“A lot of people roll their eyes when I talk about using distilled water in coolant,” Drake says. “But the average gallon of coolant is somewhere around ten dollars, and what’s a jug of distilled water? Seventy-nine cents? It’s a minor investment, but it can save the day.”

Ed Justice, Jr., with additive supplier Justice Brothers, is also a big booster of water: “It’s a little known fact that if you’ve got 50/50 coolant in your engine, and you’re low, if you top off with more coolant your engine is actually going to run hotter. You want to add water; if there’s going to be an imbalance, you want it to be on the water side.

“The problem with antifreeze/coolant,” Justice goes on, “is that you don’t really do anything to lower the temperature; all it does is stop it from boiling. It’s a better antifreeze than it is a coolant. It’s basically ethylene glycol; that’s the same thing they use to de-ice airplanes in the winter. So, it’s the best thing out there as an antifreeze, but as a coolant, it’s not that good. The simple fact that your coolant isn’t boiling over doesn’t mean that it’s any good.”


There may not be any totally foolproof method to insure that technicians are using the right coolant (and using it properly), but Shell’s Alverson offers some “obvious steps” that fleet maintenance managers can take:

  • Training and requiring the technicians to consult the OEM’s manual recommendations when in doubt;
  • Placing stickers on the radiator overflow tanks specifying the correct coolant for each vehicle in the fleet;
  • Stocking the OEM recommended coolant for each vehicle;
  • Sign-up on the work order on the type of coolant filed in to the vehicle.

“By no means should color be used as the sole indicator for the type of coolant to use,” Alverson says. “The hybrid coolants can come in red, yellow, violet, orange, blue, according to the OEM or the coolant supplier recommendations. Only on the heavy-duty side are there recommended color standards for various types of coolant.”

Still, questions remain, according to Brad Drake. “The most common question comes when it’s time to service the coolant system on a vehicle that’s been around a number of years, and the fleet manager wants to know if they have to stick with the same coolant that the vehicle came with (they don’t),” he says.

“Another common question is ‘What can I top off with?’ It can be hard to identify the coolant in the system if you didn’t put it there,” he says. “Color can tell you some things, but whan the color can’t tell you is whether the coolant employs organic or inorganic acid technology.

“Usually what will happen is, if you somehow mix organic and inorganic acids, they’ll neutralize each other and you’ll lose some of the benefits,” he explains.

Rather than take the risk of topping off a coolant system with the wrong product, Drake advises technicians to drain and flush the system completely and start from scratch.

“It’s an unappetizing suggestion, but it’s really the safest thing to do,” he says.


No matter what coolant you use in your fleet vehicles, Shell’s Alverson suggests that you monitor its quality and effectiveness with a coolant analysis program: “If you couple your coolant program with coolant analysis, you can extend your drain intervals.

“We recommend a periodic coolant monitoring program that looks at coolant concentration, the PH level, the corrosion inhibitor level (organic and inorganic), corrosion metals, coolant degradation, oxydation products, and contimination,” he says. “Pick out a few vehicles, do the used coolant testing at various mileage intervals, and see if you can’t extend the coolant drain interval.”