Coolant compatibility: Know thy coolants

Coolant compatibility: Know thy coolants

Maintenance CylinderWhen it comes to a fleet’s extended life coolant concerns, look no further than the three C’s: Capabilities; Compatibility; and Contamination. The biggest concern for the fleets running organic acid coolants (OAT) and nitrited organic acid technology (NOAT) extended life coolant [ELC] is knowing which fluid should be in their system. Extended life coolants are designed to last for at least 300,000 miles without any chemical supplementation, provided they are not diluted with additional water/conventional coolants beyond the manufacturer recommendation. Each fleet vehicle is filled at the manufacturing facility with a predetermined coolant technology. It is then a matter of following the recommendations of that OEM/engine manufacturer coolant maintenance with the correct OAT or NOAT technology.

If only it were that simple. Colin Dilley, Ph.D., vice president of technology for Prestone Products Corp., explains: “Part of the problem with following these recommendations/ procedures is knowing which coolants in the market is OAT or NOAT. It is often not clear by looking at a fluid color or reading the label. It is important that the fleet purchase their coolants from manufacturers that clearly and accurately label their products appropriately.”

It gets even more complicated if fleets have more than one type of fluid. Confusion sets in and you end up answering the question, “What coolant goes in what truck?” The simple solution to that question, if you don’t know what type of coolant you run, is to ask. There are resources available that can help fleet managers with questions: OEMs; engine manufacturers; coolant manufacturers; testing labs, industry organizations such as ATA, TMC, NARSA, SAE, etc.

One important note is to not rely solely on the coolant color to indicate the type of chemistry (IAT, HOAT, OAT, NOAT) used in the coolant. Although TMC has established recommended colors for varying types of coolants in RP-351, not all manufacturers follow the color guidelines, according to Dilley.


When coolant turns brown, it’s a tell tale sign of contamination. But where did it come from? The biggest causes of contamination are typically due to top-off/make-up with foreign coolants on the road and/or repair or maintenance work on the engine or cooling system resulting in contamination.

Prestone-Inspection-Essentials“The best way to combat contamination is to provide education and training to drivers and technicians on the importance of using the correct coolant and to avoid mixing different types of coolants,” said Fred Alverson, principal engineer, coolants, Shell Global Solutions. “Surge tank labels are also essential to identify the correct and recommended coolant for use in the vehicle.”

It’s important to keep an eye on what coolant is being added to your trucks. Hybrid organic acid technology (HOAT) is not compatible with OAT or NOAT coolants. Also, if a system was running a NOAT and someone added OAT, the nitrite level would be diluted and possibly compromise cavitation protection, explained Mike Tourville, marketing director for Evans Cooling. To combat confusion, make sure that your coolants are properly marked and clearly labeled. Also be sure your techs are thoroughly trained in the proper coolant procedures. While you might not have control over what gets added to the truck when it’s out on the road, these steps will help you mitigate your coolant contamination risk.

That said, Sean Wheatley, senior brand manager for Peak Commercial & Industrial, said that despite the desire of fleet maintenance technicians to test for the presence of nitrite, there are absolutely no concerns at all with using an OAT-nitrite free coolant as a top off with any cooling system.

“This is because the nitrite free coolants listed above incorporate corrosion inhibitor technologies that protect the cooling systems of heavy-duty cooling systems without the need to add and replenish nitrite,” he said.

When in doubt, test

If you want to find out what type of coolant is in a truck and can’t track down the answer, there are various services in which you can provide a sample of your coolant for analysis to determine the type of chemistry that is being used. In some instances, your coolant provider may be able to help you out and provide that analysis for free. Knowing your coolant is paramount in setting up a maintenance testing schedule to ensure your coolant is performing as engineered.

“A simple maintenance program should be in place by any sized fleet. Perform cooling system checks every 90 to 120 days. While it’s best to follow your manufacturer’s testing recommendations, the typical aspects you test for are color, clarity, freeze point and odor,” Peak Commercial & Industrial’s Wheatley said. “The color should be as close to your top off color as possible. Brown typically indicates a mix of coolants or corrosion such as iron oxidation (rust). Also, all coolants should be clear of debris.”

Shell’s Alverson recommended the following best practices for coolant testing in the field involve the following three tests:

1) Conduct a visual inspection: The coolant should be bright and clear, free of dirt, debris, rust and other contaminants and representative of the color of the coolant recommended for the vehicle. If the coolant appearance, clarity or color is unsatisfactory, check for possible contamination with other coolants, fuel, oil, combustion leaks, etc.

2) Test the freeze point using a refractometer: A 50/50 mixture of ethylene glycol-based antifreeze concentrate and water providing a freeze protection of -34-degrees F is recommended for most parts of the U.S., although 60/40 mixtures are sometimes used in colder regions. It is suggested that the freeze point be maintained between -24-degrees F and -49-degrees F (45-55%) for most U.S. regions regardless of coolant type and at no times should the freeze point be higher than -20-degrees F or lower than -60-degrees F. A refractometer is the most accurate and recommended method to determine the freeze protection.

3) Check the corrosion inhibitor level: ELC coolant corrosion inhibitor levels are generally maintained by ensuring the proper freeze protection and protecting against contamination with other coolants. Therefore, if the coolant appearance and freeze point are satisfactory, it is usually not necessary to test ELC coolants for corrosion inhibitor level.

Many of today’s coolants have test strips designed for the blend of ELC being used. Always check with the coolant manufacturer for details on test strips, Wheatley reminded.

You May Also Like

The 7 EV battery lessons we learned at ACT Expo

Battery experts weigh in on long-life vs. high-density, the residual value of older EVs, ethically sourcing EV battery materials and more.


For some fleets, adopting their first electric trucks might feel like taking a leap of faith simply because there are so many unknowns – many of which revolve around the true viability of the electric powertrain. What will the next generation of battery chemistries bring to trucking? Will the new electric truck you buy today hold its value better than a new diesel truck would five or 10 years down the road? How can we give higher consideration to ethics issues on the path to more sustainable operations?

Thermo King introduces the third-gen. TriPac Auxiliary Power Unit

The company says the third-generation TriPac APU is available in two different models to help customers meet emission regulations.

Western Global offers transportable, on-site refueling tank

The TransCube can be stacked up to three high when empty and two high when full.

Carrier Transicold debuts Supra eCool electric truck refrigeration unit series

The company notes that the Supra e9 and e11 units will provide comparable refrigeration performance to its diesel-powered predecessor.

The keys to properly securing unique cargo

With the wide range of cargo types, unique materials and geometric shapes and the significant mass of some loads, there is a lot to consider.


Other Posts

Cargo securement tips for International Roadcheck 2023

A brief educational triage to help you refresh your memory on proper cargo securement before International Roadcheck 2023.

Cummins, Accelera emphasize decarbonization, hydrogen at ACT Expo

The company showcased technologies including electrolyzers to produce hydrogen that can power both a hydrogen-fueled internal combustion engine concept truck and a fuel cell electric powertrain.

Hyliion unveils Karno electric range extender powertrain at ACT Expo

The Karno technology is a linear motor heat generator that leverages 3D metal-printed components and proprietary flameless oxidation technology to produce clean electricity.

Dana introduces Spicer Electrified e-Transmissions for commercial vehicles

Dana says the powertrain accommodates a diverse range of medium-duty applications, such as straight trucks, walk-in vans, refuse trucks, utility trucks and platform trucks.