Light Duty: Color By Numbers

Here's how to avoid "Coolant Confusion" in your shop.


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.

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