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Choose the Right Engine Coolant for Your Heavy-Duty Engine

Posted by Cummins Expert on

Cummins Filtration Fleetguard line of engine coolants protects your engine AND your bottom line

It may come as a surprise to some, but engine coolant is just as important as oil when it comes to maintaining your engine. Its primary function is simple but important: prevent the engine from overheating or freezing in extreme temperatures. But there are other properties of coolant that aren’t as obvious. Additives in coolants protect various engine parts from pitting, cavitation, corrosion, scaling and acidification. All of these can contribute to significant engine wear and even failure. So, it’s important to choose the right engine coolant to maximize the longevity of your heavy-duty engine.

Engine Coolant Types

Backed by 50 years of experience in the science of coolant chemistry, the Cummins Filtration Fleetguard line of coolants is designed for heavy-duty diesel, natural gas and gasoline engines. Additives protect aluminum radiator tubes from crevice corrosion and radiator perforation, and also protect the water pump and cylinder liners from damage.

There are four main types of coolant for different types of engines. Options range from lower-cost versions that need more regular service to extended life varieties that require less maintenance. Be sure to check your engine manufacturer’s specifications first to see what type is recommended for your engine. Coolants don’t have significant colors in their natural form, so they’re dyed to make it easier to identify the coolant used and to help track down leaks.  Some of the commonly used colors are red, yellow, blue, or pink, though some are purple or green.

  • Inorganic Acid Technology (IAT): The liquid that most people think of when it comes to coolant or antifreeze, IAT coolants are conventional low-silicate and typically used in cars and light-duty trucks. These are typically green or pink in color. For heavy duty engines, IATs are available pre-charged with supplemental coolant additives (SCAs) that protect the engine from pitting and corrosion. IAT coolants need more frequent service and supplemental additives to keep the coolant system working properly.
  • Organic Acid Technology (OAT): Just as the name suggests, this type of coolant uses organic acids and has extended service life. These coolants last much longer than IAT varieties and are designed for use in all heavy and light-duty diesel engines, as well as natural gas and gasoline engines. If properly maintained, some OAT coolants can provide around 1,000,000 miles or 20,000 engine hours of service without the use of SCAs
  • Nitrited Organic Acid Technology (NOAT): These are similar in service life and performance to OAT coolants, but employ nitrite and sometimes molybdate for engine liner pitting protection, which means that NOAT coolants may need to be serviced with an Extender during the life of the coolant. NOAT coolants also offer extended life and are designed for use in heavy duty ELC, NOAT and EC1 systems. (Check the manufacturer’s specifications to verify your coolant system type.)
  • Hybrid Organic Acid Technology (HOAT): This is a combination of some of the inhibitors used in IAT and OAT coolants, usually a low-silicate, nitrite/molybdate-based technology. HOAT coolants may need to be serviced with SCAs at the service intervals (typically 150,000 miles or at the manufacturer’s recommended interval), but this occurs less frequently than with IAT coolants.

Testing and Maintenance

Depending on the type of coolant you choose, you’ll need to top it off regularly with pre-mixed coolant or add back SCAs or Extenders to ensure that the coolant isn’t breaking down. You can easily check the status of your coolant with either three-way test strips or four-way test strips, depending on the coolant type.  Three-way test strips should be used with all nitrite-containing coolants to check the freeze point, and the molybdate and nitrite concentration. Four-way test strips should be utilized for OAT coolants and may be product specific, so follow the manufacturer’s recommendations for testing.  Cummins Filtration’s 4-Way Test Strips will check the freeze point, pH, and molybdate concentration, while also providing a nitrite-contamination test pad.  Test strips come with a color chart to help you decipher the readings and determine if you need to replace the coolant filter or add additives. Recommended test intervals are as follows: 

  • IAT: Every oil drain or at one year
  • HOAT: Every 150,000 miles, 4,000 hours, or one year (whichever comes first)
  • OAT: Every 300,000 miles, 6,000 engine hours, or one year (whichever comes first)

If you need to add additional coolant, it’s best to stick to one coolant when possible.  If mixing of products or brands is necessary, the best practice is to stay within one type of coolant, so for example, avoid mixing HOAT coolants with OAT or NOAT solutions, or IAT coolants with OAT solutions and vice versa. When topping up, it’s also important to make sure you’re adding at the right dilution of coolant and water. Some products are sold pre-diluted and others need to be mixed with distilled or deionized water to keep the antifreeze properties in check. Keep in mind that if you want to convert your engine over to a different coolant system, you’ll most likely need to perform a complete system drain and flush, unless your system meets the coolant manufacturer’s criteria for a controlled conversion program. While draining and replacing the existing coolant, be sure to consider the total cost of ownership over time.   It can be expensive at the outset to replace an IAT coolant with an OAT coolant for example, but it is more cost-effective over time due to the reduction in maintenance-related products and labor. If you do decide to convert a coolant system, Cummins Filtration Fleetguard has a great coolant comparison chart to help you select the right formulation.

Check out Cummins Filtration Fleetguard full line of coolants, cleaners and test strips, designed for a wide range of heavy-duty diesel, natural gas and gasoline engines.

Have further questions answered by watching the videos linked below.



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