“It was a blistering cold morning in the great white north. Seeing temps reaching -30°F, all we wanted was the car to warm up so we could start pumping hot air into the cab to defrost our mustaches. To help warm up the engine faster, we waited only a minute before heading towards the highway. Several minutes passed with no change to cabin temperature. Somewhere between minute number 7 and 10 the instrument panel was blinking a large red warning indicating that the engine was overheating. Something was wrong, very wrong,” stated a source who will remain unnamed to protect the guilty.

If you’re reading this scenario from a location which never sees subzero temps, the source of this “cold overheating” may not be obvious. Those reading from locations that see several months of snow on the ground are all too familiar with the challenges a powertrain can experience if the vehicle has not been properly prepared for a cold season.

Just as important, vehicles that never see freezing temps but are regularly exposed to 100°F temps can easily fall victim to coolant-borne problems if not properly prepared. Coolant can be a friend, just as easily as it can be a foe.

As you can see, coolant comes in many different forms, even within a single product line. Here you can see Mishimoto’s coolant concentrate, pre-mixed 50/50, and a super-concentrated coolant additive, meant to inhibit corrosion in your cooling system.

Spoiler alert; the overheated engine described previously was a victim of improper water/coolant mixture in the cooling system. The result was an overabundance of water, which froze solid during an overnight soak. When the engine was restarted, the water/coolant was unable to flow between the engine, radiator, and HVAC system to remove excess heat energy from the engine.

Fortunately, the temp sensor was in a location which allowed ice to turn to hot water, and the ECU notified the driver before the hot water turned to steam and found its way to the atmosphere through the head gasket. So why all the fuss over coolant? Let’s start with the basics.


What is Coolant?

For the majority of the U.S. market, coolant is usually one of two chemicals: ethylene glycol or propylene glycol. Both are highly soluble in water, relatively inexpensive, and both have the ability to lower the freezing point and increase the boiling point of water when mixed properly.

Also included in coolant are chemical additives which can help lubricate powertrain components which it flows through, as well as inhibiting galvanic corrosion amongst the myriad of electrochemically incompatible metals found throughout the engine/coolant system (think aluminum, steel, copper, etc). Coolants also include trace amounts of water, antifoam agents, and color dyes. For the purposes of this article, we’ll stay away from the idea of using alcohol in a cooling system, which is more common in extreme cold environments.

The constant battle of coolant is to extend the operating range of pure water. While this graph shows the high end of the temperature range, the low end is similarly altered over straight water. Then, the issue becomes choosing the right coolant for your application.

Coolant Function

When properly mixed, a coolant mixture will remove waste heat energy from an engine and “dump” that heat to atmosphere via the radiator or HVAC systems in a vehicle. Glycol based coolant mixtures can help increase and decrease water’s operating temperatures at which this is done, often at temperatures that water may not be able to do the job by itself due to freezing or the risk of flashing to vapor.

Increasing the boiling point of water is favorable because water has a higher heat transfer coefficient than steam, meaning water will transfer heat energy away from a hot engine more efficiently than steam, so keeping water in liquid form is most advantageous.

Why bother with water at all?

Sadly, glycol based coolant does have its shortcomings. Ethylene and propylene glycols are unable to transfer as much heat (energy) as pure water can. This heat transfer difference is due to the specific heat capacity differences between water and ethylene/propylene glycols. Without diving too deep into the heat transfer pool, a rough rule of thumb is that the less pure water your mixture contains, the lower its specific heat capacity or the lower its ability to absorb heat energy and move it away from an engine.

Due to this fact, running 100-percent coolant in high-heat environments can result in slightly higher operating temps, possible overheating, and potential damage to engine blocks and cylinder heads unless your engine cooling system has been sized accordingly. With its high heat transfer coefficient, it is common to see racing engines running only distilled water with an anti-corrosion additive.

While it seems to go against traditional science, Evans Cooling has developed a completely waterless coolant solution, which not only greatly increases the operating temperature range, but also doesn’t require constant fluid changes like traditional coolants.


Bridging the Gap - Water Additives

With its high heat transfer coefficient, it is common to see racing engines running only distilled water with an anti-corrosion additive. In racing or other special cases, boiling temperatures can be increased by using higher pressure radiator caps and systems. For these types of water-only applications, Mishimoto Automotive of New Castle, Delaware has formulated its special Liquid Chill Ultra Concentrated Formula to provide continued protection with anti-corrosion and lubrication properties, without the addition of glycols.

Similarly, Royal Purple’s “Purple Ice” includes corrosion inhibitors and metal passivators while containing no glycols, so it is safe to use at local track days. Chris Barker of Royal Purple notes that “Purple Ice uses a proprietary blend of surfactants to reduce the tiny air pockets that occur at the interface of the water and interior surfaces of the cooling system. Surfactants relax the surface tension of water, [which]… increases the surface wetting ability of water.” Royal Purple attributes these properties with showing a 20°F decrease in engine operating temperature (compared to pure water) during recent dyno testing. This effect is similar to the reduced surface tension one may see in soapy water.

They say good things come in small packages. This 12-ounce bottle of Royal Purple, Purple Ice mixes with six quarts of water, at the recommended ratio of 2 ounces per quart of water in the cooling systems. Since there are no glycols in the Purple Ice formula, it is 100-percent legal and acceptable for use where track rules mandate water only.

Waterless: The Other End of the Spectrum

Evans Waterless Coolant promotes a waterless coolant product and highlights extremely high (375°F) and low (-40°F) operating temperatures for its product. While waterless flies in the face of the previously mentioned “more water, more heat transfer” idea, Evans’ approach is a little different.

To avoid freezing down to -40F, Evans’ utilizes a proprietary mix of glycols and additives. On the hot side, Evans’ approach is to use that same blend to keep the coolant mixture in liquid form, even in extremely high temperature conditions. Evans’ Marketing Director Mike Tourville says, “Utilizing the idea that liquid coolant will remove heat (energy) at a higher rate than steam, if your coolant mixture is always liquid, you’re never seeing steam pockets adjacent to your cooling system.”

This illustrates the coolant jacket within a head. Area A is an area of high thermal energy transfer, where Evans Waterless Coolant is able to remain in liquid form to continue removing heat from the head. In area B, a layer of steam has formed either due to extremely high temps, or an inaccurate coolant mixture blend which didn’t increase the boiling point sufficiently.

Tourville describes this type of condition for water based coolants as “going over the vapor cliff.” He explains, “This is where customers of Evans Waterless Coolant really benefit. When steam occurs, you’ll see heat transfer reduced to about four-percent of the effectiveness of water. But Evans boiling point far exceeds water/coolant mixture specifications, despite what pressure radiator cap you choose. So you should expect to see far superior protection from Evans, that’s what you’re really paying for.”

Admittedly, Evans does not intend to replace the coolant in every stock vehicle on the road. Evans’ intent is to be utilized in performance markets and applications where a customer intends to retain a vehicle for an extended period of time. Evans is also aimed at protecting that classic vehicle engine during long parades, where there is little to no airflow to help to cool the system, or custom or off road vehicles which have an “overheating problem.” Additionally, where environmental conditions are at their extremes, Evans is confident in its ability to help avoid freezing and boil over situations.


The Coolant Rainbow

Coolants are colored to facilitate visually identifying mixtures that include coolant, as well as to identify liquid levels in tight or dark spaces (such as looking down into a dark radiator). Both ethylene and propylene glycols are naturally colorless, so it is important to differentiate them (visually) from water or lightly tinted oil. This can come in handy when trying to differentiate coolant from say, drinking water.

Historically, ethylene based coolant was toxic when consumed (in volumes greater than 3 ounces), although manufacturers are attempting to reduce toxicity levels by using propylene in some applications. While coolant colors are simply a result of chemical dyes, Ricky Nietubicz of Mishimoto Automotive points out, “There are some color patterns you will see for certain products like green to yellow for normal coolant, or yellow to orange for longer life coolant. Typically speaking, coolant can be any color the manufacturer desires.”

Different coolants often have different dyes in them to be able to not only differentiate them from pure water, but in some cases to also denote their specific capabilities.

Correct Mixing

It cannot be overstated; read the directions printed on the coolant bottle before mixing. The manufacturer should provide both general mixture instructions as well as suggested mixture ratios relative to your local environment/ambient temperatures. Mishimoto always suggests mixing water and coolant “prior to filling the system. In a case where a system is being topped off, only a few minutes of engine idle are necessary for the resultant mixture to be homogenous.” For applications that allow glycol based coolant (almost all non-race applications), Mishimoto’s standard 50/50 mixture easily operates within a -26F to 265F temperature window.

Second, buy a coolant mixture gauge. They are inexpensive and easy to use. One great example of a water/coolant mixture test unit is manufactured by Thexton Manufacturing. Test units come in two sizes, and are built for testing Ethylene and Propylene based glycol coolants. Just make sure to order the proper (ethylene or propylene) test unit for your application. Thexton VP of Engineering, Dennis Harder confirmed that almost all coolants on the market are ethylene based. “If it says Dex-Cool or any other description except ‘low-tox,’ it’s highly likely to be ethylene glycol,” says Harder. “The few exceptions to that rule are a few Bobcat equipment pieces and limited Arctic Cat applications.”

Coolant mixture testers come in a few varieties. The keys to accurate measurement are to make sure you have the correct tester for the type of coolant you are using, and that you are testing at the temperature the tester was designed for. Some offer temperature compensation to make the testing process a little easier.


To test water/coolant mixture, simply insert the test unit into the mixture and use the squeeze bulb to suck mixture into the test tube (think turkey baster) which contains floating test discs. Compare the number and color of floating discs to the chart on the gauge packaging to determine what temperature the mixture is best suited for.

“For most mild applications, observing the fourth, white disc floating in the test unit confirms anti-freeze properties down to -15°F. If your environment warrants a colder mixture, just follow the directions after adding additional coolant to the mixture,” Harder explains. “If the orange, sixth disc is floating, you either have too much coolant in the mixture, or you need to inspect for other issues.”

Lastly, confirm that the coolant is at the proper temperature to be tested. Texton stressed that its test units include temperature compensation, allowing testing at varied coolant temperatures, which many of the import test units do not compensate for. Avoid making an inaccurate reading by following these recommendations.

“While universal coolants can be mixed [with each other], it is impossible to know the exact chemical properties of the resultant mixture” states Mishimoto’s Nietubicz. He warns, “Mixing different dyes makes it impossible to make any sort of visual assessment of the resultant mixture.”

From the Hose or Bottle - Distilled vs. Tap Water

“Distilled water is a readily available, and inexpensive, form of purified water that has had most minerals and other contaminants removed,” says Mishimoto’s Nietubicz. “Tap water can vary substantially from region to region in terms of mineral content and chemistry. These differences can change how the coolant performs, potentially reducing key traits like lifespan or boiling point.”

Nietubicz believes there is no hard and fast universal service frequency. “It depends on the particular coolant, and the usage of the vehicle. We have engineered the [Liquid Chill] coolant to meet or exceed every manufacturer specification, so users can be confident that their engines will be protected when they follow their manufacturer recommended maintenance schedule.”


If you’re operating in an environment that sees extreme highs and lows, plan to check your mixture before each extreme season. Be proactive here, your engine will thank you. If you’re using a product such as Evans Coolant, the Evans’ suggested replacement is, well, never. Evans states that as long as the product does not become contaminated by more than 5-percent water, or any additives, the product does’t require replacement. A word to the wise, propylene glycol should be replaced when it turns a reddish color, as this is a sign of iron corrosion (block material) within the liquid.

The Dreaded Premix Debate

This debate never seems to end, so let’s keep it simple. Figure out what a gallon of pure coolant will cost and add $1.00 (which is roughly the price of a gallon of distilled water). Now compare that price to buying two gallons of pre-mixed coolant. While more convenient, only you can decide whether that convenience is worth the price differential.

Nature’s ideal coolant, water, has spent over 100 years in the modern internal combustion engine and has mostly satisfied the needs for heat transfer and avoiding catastrophic engine failure. Sometime around the 1920’s ethylene glycol was added to the mix to further expand the operational limits of water, helping improve heat transfer performance, especially in extreme temperature environments.

More recently, products such as Evans Waterless Coolant has taken the water out of the equation, while still maintaining function. Is this analogous to the horseless carriage, the wireless phone, or the driverless car? Maybe not just yet, but depending on your vehicle, your performance application, and the environment in which you operate, you’ll want to take a close look at how you mix (or don’t mix) your coolant to insure long and cool engine life.