How to Choose the Right Coolant for Your Heavy-Duty Equipment
Combustion engines produce a lot of heat that needs to be controlled, managed, dissipated and removed from the engine. The function of coolant is to circulate this heat through the cooling system, ultimately removing it.
Although all coolants serve the same purpose, they’re not all created equal. There are also a lot more choices today than there were a generation ago. Understanding the pros and cons of different coolant types and their maintenance needs is critical because the type of coolant you use, and how well you maintain it, can have huge impacts on your engine’s performance and lifespan. According to a frequently cited technical paper published by the Society of Automotive Engineers (SAE), roughly 40% of all problems in heavy-duty diesel engines are related to the cooling system.
What's in a Coolant?
Coolant is typically composed of three major elements: water, a base (usually glycol) and an additive package.
Water was the original engine coolant and remains a standard component because it’s naturally good at conducting heat away quickly and efficiently. But the quality of the water matters. Hard water, for example, can cause scale buildup in your engine, leading to costly repairs. Use a premixed 50/50 coolant, rather than mixing it from concentrate, to ensure you have a water source that meets industry standards.
The purpose of the glycol base is to raise the boiling point and lower the freezing point of the water, which expands the temperature range in which the coolant can work properly. Like water, glycol is also a great heat conductor.
The simplest and most commonly used base is ethylene glycol (EG), which is mildly toxic but offers the best protection against freezing. Propylene glycol (PG) coolant is typically less common and more expensive than EG, but has the advantage of being non-toxic. PG also freezes at higher temperatures, making it less suitable for cold weather conditions.
While the water and base components primarily manage engine temperature, the additive package protects your engine by preventing cylinder liner pitting, scale formation, water pump cavitation, erosion, and other types of chemical-related damage. The additive package is also what determines most of the differences between coolant brands and technologies.
Coolant has a useful life, much like engine oil, because the additives deplete over time. As conventional coolants age, their chemical properties can be replenished by using supplemental coolant additives (SCAs). Routine testing will help you determine the proper dose of additives needed to restore coolant effectiveness.
Not Sure Which Coolant Is Right for You?
Use the Fleetguard online coolant picker tool to find the ideal coolant based on your engine type and current product. It’s the best way to ensure your engine receives the maximum coolant protection.
Whichever you choose, all Fleetguard coolants are backed by an industry-leading, non-prorated warranty.
FIND YOUR COOLANT
Don’t Be Misled by Coolant Color
Many people use color to describe different types of coolant; you’ll frequently hear them refer to red, green, blue, yellow or pink as the “type” of coolant they’re using. Although this has been a common practice for decades, it isn’t a good idea because coolant colors aren’t standardized across the heavy-duty industry. Manufacturers use different colors for the same coolant technologies and vice versa.
To determine if a coolant is appropriate for your engine, always check its labels to understand the designated technology type, and whether it’s manufactured in accordance with best practices (see below).
Performance Specifications
There are a few numbers to keep in mind when choosing a coolant. The first two are defined by the American Society for Testing and Materials (ASTM):
- ASTM D3306: Coolants in this class are designed for light-duty engines, such as automotive-grade applications. They’re not designed to provide the types of protection a heavy-duty diesel engine requires.
- ASTM D6210: This specification is the bare minimum you should look for to protect any heavy-duty diesel engine.
In addition, many original equipment manufacturers (OEMs) have specifications of their own, which are often stricter than ASTM standards. They’re typically based on in-house testing protocols to determine which coolant technologies and standards work best with their unique equipment designs. A good example of these is Cummins engineering standard (CES) 14603, which is used to indicate products designed and approved by Cummins to work with their specific engines, systems and applications.
Coolants by Technology Type
Here’s a quick rundown of the most common coolant technologies and the Fleetguard products recommended for each type.
Conventional, or inorganic additive technology (IAT), coolant is almost as old as the automobile. This is the coolant your grandfather used “back in the day” because there wasn’t anything else to choose from. The additive package is typically some combination of nitrite, molybdate, borate and/or phosphate. We recommend Fleetcool™ for conventional applications.
Although conventional coolants are familiar to most technicians and have the lowest sticker price, you’ll need to budget for more than just the up-front cost of the coolant itself. In addition to needing SCAs to maintain effectiveness, they require the most maintenance. For best performance, they should be tested every time you drain the oil and be replaced every 300,000 to 400,000 mi (482,800 to 640,700 km). The additional supplies, labor and downtime add up, ultimately making conventional coolants the most expensive option over time.
Hybrid, HOAT (hybrid organic acid technology) or ELC (extended life) coolants blend conventional additives like nitrite, borate, molybdate and/or phosphate with organic acids typically found in OAT (organic acid technology) coolants. Although this combination is less effective than a pure OAT formulation, it significantly extends coolant life and requires less maintenance when compared to conventional products.
Like conventional coolants, hybrid coolants must still be recharged periodically with SCAs, but they don’t need to be tested or serviced as often. They should be checked every 150,000 mi (240,000 km), every 4,000 hours or at least once a year — whichever comes first.
Fleetguard ES Compleat™, the most common coolant used to test and validate Cummins engines, is a hybrid coolant designed to last for the life of the engine with proper testing and maintenance. Fleetcool EX™, a phosphate-free hybrid approved for use in legacy Detroit diesel engines, offers a similar lifespan.
NOAT (nitrited organic acid technology) formulations are low-maintenance coolants designed for systems that require nitrites. They’re less susceptible to contamination than hybrid or conventional coolants and require no SCAs. NOAT coolants require extenders at 600,000 mi (965,600 km), but are otherwise good for the life of the engine with occasional top-ups. Fleetguard ES Compleat NOAT is compatible with systems requiring nitrite, such as Cat EC-1.
OAT (organic acid technology) coolants are preferred by most OEMs because they offer excellent performance, the longest service intervals and coolant life, and the least maintenance. No SCAs or extenders are required; you can simply top off with additional OAT as needed. Like NOAT, it offers the most robust contamination protection. In addition, it provides superior compatibility with aluminum.
Fleetguard ES Compleat OAT is suitable for all makes and models, including diesel, gasoline, natural gas, and battery electric vehicles, making it a wise choice for mixed-fleet operations. It’s free of nitrites, amines, phosphates and silicates, so it won’t harm your engine. It offers customers and OEMs the best technology, lowest total cost of ownership and simplest maintenance.
Red Flags to Watch For
2-EH
Many OAT and NOAT coolants available on the market today contain 2-ethylhexanoic acid (2-EH or 2-EHA). The low cost of this additive makes it popular with many engine OEMs and coolant manufacturers, but it’s extremely aggressive to the silicone seals often used as head gaskets and hoses and will cause damage to those systems.
All Fleetguard coolant products are 2-EH free. They’re compatible with all modern system gasket and hose materials, so you won’t have to worry about leaks or cracks.
Recycled Coolant
Recycled coolant can sound like a good idea that offers cost savings and comes with sustainability benefits. Unfortunately, there are no industry standards for it. Fleetguard laboratory tests have found that many recycled coolants are little more than colored water mixed with harmful chemicals that could damage your engines. Although there are a few legitimate recyclers out there, they’re usually cost-prohibitive compared to new coolant, so it’s best to stay clear of these products.
Universal Conventional Coolants
This is an old-school approach that turns automotive-grade into heavy-duty coolants by adding SCAs. They’re classified under ASTM D4985. If you see that code on the label with no mention of ASTM D6210, you’ll want to choose something else. Even though these products appear to be inexpensive heavy-duty coolants, you’ll discover that you need to add a bunch of stuff to them when you read the fine print. In the end, you’ll pay more for and get less usable life.
Maintaining Coolant Additive Levels
The useful life of a coolant ends under either of the following conditions:
- The chemical additives in the coolant are outside acceptable limits. (Typically, this is caused by topping off with a concentrate or water only or by failing to conduct maintenance at the recommended service intervals.)
- Contaminants in the coolant exceed published limits.
- If you’re using a conventional or hybrid coolant product, you’ll need to add SCAs to replenish the system. Use Fleetguard DCA2 to recharge Fleetcool and Fleetcool EX coolants, or DCA4 for ES Compleat or similar technology.
How Often Should I Test?
Conventional coolants should be tested at every oil drain or annually (whichever interval is shorter). Hybrid coolants should be tested every 150,000 mi (240,000 km)/4,000 hours or annually. OAT or NOAT should be tested every 300,000 mi (480,000 km)/6,000 hours or annually.
A variety of Fleetguard brand testing kits and maintenance tools are available.
Test strip kits provide a quick way to understand the condition of your coolant by measuring sulfate, chloride and pH levels. QuikChek 3-Way Test Strips are easy to use and minimize unnecessary draining of coolant that’s still within specifications. Learn how to use them in this short video.
If you’re mixing and blending coolant with your own water source, you should be testing that water to understand its hardness, pH and chloride levels. If any of these levels are in the no-pass range, you’ll want to consider changing your water source. Distilled, deionized or reverse osmosis (RO)-treated water are generally good sources. Water-Chek 3-Way Strips provide a quick way to determine if your coolant make-up water meets OEM, American Trucking Associations’ Technology & Maintenance Council, and/or ASTM specifications or recommendations. Learn how to use them here.
If you’re using a coolant that contains nitrite (including all Fleetguard coolants, except ES Compleat OAT), Fleetguard 3-Way SCA/Freeze Point Strips will help you understand how well protected your engine will be in cold weather. They measure freeze point as well as molybdate and nitrite levels. Comparing the color readout on the test strip to the included chart will tell you the exact amount of each additive you need to put back into the system. They’re available in imperial or metric units. Learn how to use them in this video.
Designed specifically for use with ES Compleat OAT, the 4-Way ES Compleat OAT Test Kit will help you understand whether you need to top off with more OAT or add water to dilute the system. OAT products are a newer technology with more differences from one brand to another, so it’s essential to use Fleetguard OAT test strips with Fleetguard OAT products. Get quick instructions in this video.
Refractometers determine freeze point protection more accurately than test strips or float-type hydrometers. They’re highly recommended for anyone who tests coolant regularly, but especially for users in climates that experience cold winter weather. Fleetguard refractometers are available for different types of coolant: ethylene or propylene glycol, and ES Compleat OAT. Learn more about refractometers here.
Finally, coolant filtration is proven to maintain and reduce wear on all cooling system components, regardless of the type of coolant you use. In addition, chemical water filters can provide a convenient and reliable method for delivering supplemental coolant additives into the cooling system to improve performance and prolong the usable life of hybrid and conventional coolants. A suite of Fleetguard brand coolant filters — including standard service, extended service, chemical and non-chemical types — are available. Contact your Fleetguard representative if you would like help selecting the best coolant filter for your equipment needs.
