Selecting the Right Extended-Life Coolant (ELC)

An overheated engine is an expensive headache. Whether you’re operating one vehicle or an entire fleet, it’s important to get your coolant right. This is especially true for modern engines that have more and more aluminum in them, which can be damaged by extended-life coolants (ELC) that contain nitrites. (You’ll also see the broad category of all ELC referred to by the acronym AFC, which stands for antifreeze/coolant.) 

To make the whole thing a bit more confusing, the color-coding system that antifreeze/coolant used in the past does not apply nearly as universally as it used to because manufacturers have added dyes to help their products stand out. 

Not All ELCs Are the Same

There are a few broad categories and common acronyms you need to know to select the right antifreeze/coolant for your heavy-duty engines:

• IAT—Inorganic acid technology
• OAT—Organic acid technology
• HOAT—Hybrid organic acid technology
• NOAT—Nitrited organic acid technology

IAT coolant utilizes borates, nitrites, silicates, phosphates, and other inorganic salts to protect metal surfaces. An IAT coolant will deplete over time. An IAT coolant will also require a supplemental coolant additive (SCA) or extender.

OAT coolant uses organic acids instead of ethylene glycol. It protects well against corrosion, deposits, and cavitation erosion. OAT coolants have been used in heavy-duty trucks for many years and are fairly common partly because they can last so long. 

HOAT coolant offers the best of both worlds and has both silicates and organic acid to protect your engine. An HOAT coolant has the corrosion resistance of IAT coolants and the long life of OAT coolants. An HOAT coolant may require an SCA or extender to be added to your system.

NOAT coolant will have nitrite organic acids in it. It is suitable for heavy-duty engine cooling systems. Both NOAT and HOAT have similar performance characteristics, so it’s important to refer to the recommendations of your original equipment manufacturer (OEM) to select what is right for your vehicles. 

This Coolant Cross-Reference Guide covers which coolant manufacturers’ products fit into which categories (and what color each is). It’s a handy sheet of paper to have when you’re comparison shopping. 

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• Shell Rotella ELC Pre-Diluted 50/50—55-Gallon Drum
• Shell Rotella ELC Concentrate—55-Gallon Drum
• ShellZone Dex-Cool Concentrate—55 Gallon Drum
• ShellZone Dex-Cool Pre-Diluted 50/50—55 Gallon Drum
• ShellZone Multi-Vehicle Concentrate—55 Gallon Drum
• ShellZone Multi-Vehicle Pre-Diluted 50/50—55 Gallon Drum
• ShellZone Antifreeze Concentrate—55 Gallon Drum
• ShellZone Antifreeze Pre-Diluted—55 Gallon Drum
• Shell Rotella ELC Nitrite-Free Concentrate—55-Gallon Drum

Remember Keller-Heartt doesn’t charge a delivery fee on most orders so keep that in mind as you’re calculating your savings.

Coolant Rules of Thumb

1. Do not mix different types of coolants.
2. Both OAT and NOAT coolants require little maintenance, but be sure to keep the system full. You also need to maintain the correct mix of coolant and water for your vehicle. For some vehicles, you can convert a nitrite-free coolant to NOAT. Here’s a guide on how to do so with Shell Rotella.
3. New vehicles or ones with a rebuilt radiator may do better with a one-time conditioner treatment to protect the aluminum if you’re going to use a HOAT ELC.
4. IAT coolants need additive concentration testing and SCAs. OAT generally does not require frequent SCA additions.
5. Fleets should perform coolant system tests every three to four months and follow the guidelines from their manufacturers for maintenance.

Diluted or Concentrated?

Keeping the right mix of water to coolant in engines is important. You can opt to buy ELC that is concentrated and dilute it yourself, or you can buy it pre-diluted so it comes ready to use immediately.

Here are some more handy resources to ensure your investment in antifreeze/coolant pays off with long vehicle life:

• Information on Acustrip test strips, which can help you know when your Shell Rotella Antifreeze OAT or NOAT needs service.
• Trying to decide if you need nitrite-free ELC for your equipment? Download this heavy-duty engine chart that lists the major manufacturers and which Shell Rotella coolants are approved and recommended.

If you’re spending a lot of money on coolant/antifreeze and are not already buying in bulk, we’d be happy to answer any questions you have about how much you could save by partnering with Keller-Heartt on these critical fluids.