Engine coolant is just as important as oil when it comes to maintaining your engine. Today’s coolant formulations are more advanced than ever, but the fact remains that 50% of all premature engine failures are related to cooling system performance. Cooling systems are often neglected but unresolved issues within the coolant can rapidly lead to much bigger problems relating to engines, transmissions, or hydraulics.

Coolants come in a rainbow of colors depending upon the type of formulation and manufacturer.  Currently, there is no industry standard manufacturers must follow when selling their products. As a result, coolant system maintenance can be more challenging.

Coolant Colors

Choosing the right engine coolant can help maximize the longevity of your heavy-duty engine. In a new vehicle, coolant is added by the manufacturer based on the specifications for the engine. However, identifying the coolant currently in your cooling systems can be much more difficult.

Coolant and water are clear liquids. Until recently, coolant/antifreeze color was predominantly dyed green for light-duty and heavy-duty engine cooling systems. With the introduction of long life (LLC) / extended life coolants (ELC), manufacturers began to use different dye color identify coolant types. Color also makes it easier to track down coolant system leaks.

The four main types of coolant and their colors are:

• Inorganic Acid Technology (IAT): Conventional low-silicate coolants typically used in cars and light-duty trucks. For heavy-duty engines, IATs include supplemental coolant additives (SCAs) that protect the engine from pitting and corrosion. Color: predominantly bright green.
• Organic Acid Technology (OAT): This type of coolant uses organic acids and has extended service life. OAT coolants are designed for use in heavy and light-duty diesel engines, as well as natural gas and gasoline engines. Color: orange or red, but can also come in yellow, blue, red and dark green depending on the manufacturer.
• Nitrited Organic Acid Technology (NOAT): NOAT coolants contain nitrite and sometimes molybdate for engine liner pitting protection. Color: Typically red
• Hybrid Organic Acid Technology (HOAT): These coolants combine the best of IAT and OAT products offering corrosion resistance for aluminum parts and rustproofing for iron components. Color: typically, yellow or orange, but can also be pink, purple, and blue.

As you can see, color is not always the best indicator of the type of coolant within a cooling system.

Problems with Mixing Colors

Mixing coolants can cause chemical reactions in the coolant reservoir. Mixing a green (IAT) with an orange (OAT), for example, can cause a brown gel-like sludge to form which can block the cooling system over time.

Consider also red coolants (OAT, HOATs and NOATs) – these can be both nitrite and nitrite-free blends. If two red coolants of differing blend are mixed, it can significantly reduce engine protection with not enough of the right additives left in the mixed formulation to protect against corrosion. 

Identifying Coolant in Your System

With single OEM fleets, it may be easier to identify coolant because a consistent manufacturer recommended coolant is being used. However, with mixed fleets and older fleets, you could see a variety of coolants being used. New, old, mixed, or single OEM – you are almost guaranteed that coolant top-offs are happening outside of regular maintenance schedules. These issues create difficulties in identifying what is being used especially because color is not a clear guide. See a purple coolant in the reservoir? This could be a mix of two different coolant types.

A good place to start is with the engine manufacturer. Confirm the recommended coolant type for your engine and situation. Add in regular coolant analysis based on the recommended test internals to proactively identify if a coolant mix issue has occurred.

Discrepancies between the recommended and actual coolant in the system may necessitate a drain and replace of the existing coolant to maintain optimum engine protection.

Be sure to also implement more stringent controls for those “between maintenance” coolant top-offs to ensure the right coolant is added…and not just any coolant.

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