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CHAPTER 2

COOLANT SELECTION

Coolant is one of the most important components of your high-performance cooling system. It should never be overlooked because it transfers heat from the engine to the radiator, protects the engine and the cooling system from rust and corrosion, and prevents freezing in cold climates.

Most automotive engines are water-cooled to remove waste heat. Although the term water actually means a coolant composed of antifreeze and water, not water alone. The automotive industry uses the term engine coolant, which covers its primary function of convective heat transfer for internal combustion engines.

Coolant Is Antifreeze and Water

All coolants are a mixture of antifreeze and water, with the exception of the waterless racing type. Water is best at absorbing more heat per gallon than any other liquid coolant, but if it was used alone it will cause corrosion in the engine. The purpose of antifreeze is to prevent the engine block from bursting due to expansion when water freezes.

Antifreeze is an additive that lowers the freezing point of a water-based liquid and also increases its boiling point. An antifreeze mixture is used to achieve freezing-point depression for cold weather and also achieves boiling-point elevation to allow higher engine temperatures. Freezing and boiling points are properties of a solution that depend on the concentration of the dissolved substance.

Commercially, both the additive (pure concentrate) and the mixture (diluted solution) are called antifreeze, depending on the context. Corrosion inhibitors are added to help protect the radiators and cylinder water jackets from corrosion. Water pump seal lubricant is also added to the coolant mix.

Careful selection of an antifreeze can enable a wide temperature range in which the mixture remains in the liquid phase, which is critical to efficient heat transfer and the proper functioning of heat exchangers.

Water

Water is the principal ingredient in coolant because it is inexpensive, is a very efficient heat exchange fluid, and has excellent thermal conductivity. Water also has a good specific heat. However, it freezes at 32°F (0°C) and boils at 212°F (100°C).

Water is the best coolant in terms of heat conduction, but it is also the best source of corrosion. If you are using straight water, you should always add a water pump lubricant and a corrosion inhibitor. You can also use a coolant enhancer such as WaterWetter, which improves surface tension and heat conductivity.

What is engine coolant? Coolant is a mixture of about 50 percent water, 47 percent antifreeze (ethylene glycol or other antifreeze), and 3 percent corrosion inhibitors and other additives.

Water Quality

The American Society for Testing and Materials (ASTM) standards for water quality are:

Chloride	Less than 40 ppm
Sulfate	Less than 100 ppm
Calcium	Less than 100 ppm
Magnesium	Less than 100 ppm
Total Hardness	Less than 170 ppm
pH Range	5.5 to9.0
Iron	Less than 1 ppm

* ppm = parts per million ■

Coolant manufacturers often suggest a 50-50 mix of ethylene glycol and water, which will protect your cooling system to -34°F. If using an ethylene glycol and water mix, it is also recommended to use distilled water to keep minerals out of the cooling system. Today, antifreeze already mixed with water can be purchased.

Ethylene Glycol

French chemist Charles-Adolphe Wurtz first synthesized ethylene glycol in 1856. However, not much was done with it until the 20th century. In 1917, ethylene glycol was first produced commercially for use in the manufacture of dynamite.

In addition to being an effective substitute for glycerol in the manufacture of high explosives, ethylene glycol also turned out to have characteristics that made it an ideal antifreeze coolant. It would mix readily with water in any proportion, and it has a lower freezing point and a higher boiling point than water. Ethylene glycol was first used as an automotive antifreeze in 1926.

Ethylene glycol solutions have been used as a permanent antifreeze since the higher boiling points provided advantages for summertime use as well as during cold weather. Ethylene glycol oxidizes to five organic acids (formic, oxalic, glycolic, glyoxylic acid, and acetic acid). Inhibited ethylene glycol antifreeze mixes are available with additives that buffer the pH, slow corrosion to protect the engine metal, and reserve alkalinity of the solution to prevent oxidation of ethylene glycol and formation of these acids. Nitrites, silicates, borates, and azoles may also be used to prevent corrosive attack on metal. Only the ethylene glycol is permanent; the corrosion inhibitor and other additives will wear out.

Ethylene glycol was the base antifreeze used in evey OEM factory fill in the past. It was the familiar green coolant used in all makes and models of cars and trucks. The additive package varied by manufacturer. (Photo Courtesy Jim Halderman)

Ethylene glycol is poisonous to humans and other animals, and it should be handled carefully and disposed of properly. Its sweet taste can lead to accidental ingestion or allow its deliberate use as a murder weapon. Ethylene glycol is difficult to detect in the body. Its metabolism produces calcium oxalate, which crystallizes in the brain, heart, lungs, and kidneys, damaging them. Symptoms include intoxication, severe diarrhea, and vomiting. Depending on the level of exposure, accumulation of the poison in the body can last weeks or months before causing death, but death by acute kidney failure can result within 72 hours if the individual does not receive appropriate medical treatment for the poisoning.

Ethylene glycol was used for a variety of automotive applications, but there are lower-toxicity alternatives made with propylene glycol along with the newer organic hybrid antifreeze.

Embittered Ethylene Glycol

Newer ethylene glycol antifreeze mixtures contain the embittering agent denatonium benzoate to discourage accidental or deliberate consumption. Denatonium benzoate is very bitter. Just a small amount will make coolant so bitter that pets will not be able to swallow it.

Embittered equals awful tasting. The embittering agent (denatonium benzoate, 30 ppm) has been required in California and Oregon since 2004. It prevents the death of animals that might drink ethylene glycol due to its sweet taste. (Photo Courtesy Jim Halderman)

There are 12 US states that require antifreeze to have the embittering agent. They are: Arizona, California, Maine, New Jersey, New Mexico, Oregon, Tennessee, Utah, Virginia, Vermont, Washington, and Wisconsin. Illinois, Massachusetts, New Hampshire, and Ohio are working on passing a similar rule.

Propylene Glycol

Propylene glycol is considerably less toxic than ethylene glycol and may be labeled as nontoxic antifreeze. It is used as antifreeze in situations where ethylene glycol would be inappropriate, such as in water pipes in homes.

Propylene glycol oxidizes when exposed to air and heat to form lactic acid. If not properly inhibited, it can be very corrosive, so pH buffering agents such as dipotassium phosphate and potassium bicarbonate are often added to prevent acidic corrosion of metal components. In the absence of inhibitors, propylene glycol can react with oxygen and metal ions, generating various compounds including organic acids (e.g., formic, oxalic, acetic). These acids corrode metals in the system.

To prevent corrosion, pre-inhibited propylene glycol solutions can also be used instead of pure propylene glycol. When a solution of propylene glycol in a cooling or heating system develops a reddish or black color, this indicates that iron in the system is corroding and it should be replaced.

Propylene Glycol is sold by only a few companies, and one of the best versions is AMSOIL Propylene Glycol Antifreeze & Coolant (ANT). AMSOIL formulated ANT to provide benefits beyond those in conventional antifreeze and coolant products. Unlike toxic ethylene glycol–based products, AMSOIL Propylene Glycol Coolant has low toxicity, limiting the threat to children and animals. It is also biodegradable and provides maximum cooling system protection in extreme temperatures and operating conditions. The FDA has classified propylene glycol as an additive that is generally recognized as safe for use in food. (Photo Courtesy AMSOIL)

FDA Approval

The Federal Drug Administration (FDA) allows propylene glycol to be added to a large number of processed foods. It is found in ice cream, frozen custard, salad dressings, and baked goods along with the e-liquid used in electronic vapor cigarettes.

Some manufacturers do not recommend the use of propylene glycol antifreeze. Check the recommendation in the vehicle’s owner’s manual or online service information before using it.

Inorganic Additive Technology

Inorganic additive technology (IAT) is the traditional green coolant used in older vehicles. This solution can contain silicates (possible abrasive dropouts), phosphates, and borates. It offers fast-acting corrosion protection, but the additives are quickly consumed. Once gone, the cooling system is exposed to possible corrosion problems, so it had to be changed regularly.

Inorganic acid technology (IAT) contains either ethylene glycol or propylene glycol. It is mainly built up with silicate or phosphate additives to increase its compatibility with metal cooling system components. Most will recognize it as the original green or blue antifreeze. The recommended replacement interval is every year. (Photo Courtesy Jim Halderman)

IAT is considered obsolete. It is no longer used because it can cause early failure of ceramic phenolic seals used in the newer water pumps.

Antifreeze Types

As the need for antifreeze grew, manufacturers became increasingly aware of the different needs for each region. They began to use different compounds and formulas to suit specific areas of the world.

European countries had extremely hard water. Since coolant is a 50-50 mix of antifreeze and water, water quality drastically impacts the overall mix. European manufacturers began to move away from phosphate-based technology because of its tendency to form scale.

On the other side of the world, Japanese manufacturers began to move away from silicates. They were avoiding issues with silicate gel drop out.

Organic Acid Technology

Organic acid technology (OAT) is an ethylene glycol–based antifreeze found in Dex-Cool. It is the coolant of choice for General Motors, Volkswagen, and many Japanese and Asian vehicles. This formula is engineered to offer long-life corrosion protection. It was originally made by Texaco and was first used in the GM 6.5L diesel engine. It was used exclusively by General Motors in some buildout 1995 models and all 1996 cars and trucks except Saturn and Geo.

GM Dex-Cool’s formula was engineered for corrosion protection. The downside of OAT is it is not compatible with other types of coolant (IAT and HOAT). In fact, Ford, Chrysler, and others say not to use this type of coolant in their newer vehicles.

Dex-Cool antifreeze uses two inhibitors: sebacate and ethylhexanoic acid (2-EH) as corrosive inhibitors. Dex-Cool has a bright orange color and its inhibitor formula forms a film on aluminum surfaces that protects these surfaces from corrosion. The disadvantage of using OAT is that it is not compatible with other types of coolant (IAT and HOAT). Also, 2-EH tends to damage plastics, such as nylon 6.6 that is used in intake manifold gaskets and radiators. There are two OAT coolants that do not use 2-EH: Peak Global OAT and G30 OAT.

There are a number of class action suits against General Motors, and they may have to pay for intake gaskets on V-6s and V-8 engines. Some of these vehicles exhibit brown gunk and rust in their cooling systems along with intake manifold gasket failures. The root cause of this brown gunk is air entering the system and causing rust. Rust in the system then causes blockages. Ford, Chrysler, and others say to not use Dex-Cool in their newer models. Originally, it had a service interval of 150,000 miles or 5 years, but that has been downgraded to 2 years or 30,000 miles.

Dex-Cool’s bright orange color is very distinctive. It is not the green coolant that you grew up with! (Photo Courtesy Jim Halderman)

Prestone and Valvoline market organic acid technology (OAT) antifreeze coolants that meet the GM Dex-Cool specification, but they are not as expensive as the GM Dex-Cool-labeled products due to not having to pay royaltys to General Motors. Vehicles are built with OAT antifreeze (Dex-Cool) or with hybrid organic acid technology (HOAT) formulation (Zerex G-05), both of which claim to have an extended service life of 5 years or 150,000 miles.

The real culprit appears to be operating vehicles for long periods of time with low coolant levels. The low coolant is caused by pressure caps that fail in the open position. This exposes hot engine components to air and vapors, causing corrosion and contamination of the coolant with iron oxide particles. This in turn can aggravate the pressure cap problem, as contamination holds the caps open permanently. New caps and recovery bottles were introduced at the same time as Dex-Cool. To avoid this issue, check the radiator pressure cap as outlined in chapter 7 and replace the cap if it won’t hold the right pressure.

G-Coolants

Glysantin is an engine coolant created by BASF in Europe and Valvoline Zerex in the United States. These are the coolant types listed by G number:

G05: Different from Dex-Cool in certain amounts of additives

G30 and G34: Non-silicate and phosphate free

G11: Blue, Volkswagen before 1997

G12: Pink/red, Volkswagen 1997+ or purple, Volkswagen 2003+; HOAT formulation and phosphate free

G48: Blue, low silicate and nitrate, amines, and phosphate (NAP) free ■

Prestone Extended Life is an OAT coolant that is compatible with any antifreeze that meets the Dex-Cool specification. It is less expensive than Dex-Cool products. According to some Dex-Cool manufacturers, mixing a green non-OAT coolant with Dex-Cool reduces the batch’s change interval to 2 years or 30,000 miles but will not cause engine damage.

Honda and Toyota created new extended life coolants that use OAT with Sebacate but without the 2-EH. Some added phosphates provide protection while the OAT builds up. Honda specifically excludes 2-EH from its formulas. Typically, OAT antifreeze contains an orange dye to differentiate it from the conventional glycol-based coolants (green or yellow). Some of the newer OAT coolants claim to be compatible with all types of OAT and glycol-based coolants; these are typically green or yellow in color.

Hybrid Organic Acid Technology

A newer version of OAT technology is called hybrid organic acid technology (HOAT). It is similar to the OAT-type antifreeze in that it uses organic acid salts (carboxylates) that are not abrasive to water pumps yet provide the correct pH. If the pH is too high, the coolant can cause scaling and reduce the heat transferability of the coolant. If the pH is too low, the resulting acidic solution could cause corrosion of the engine components exposed to the coolant.

HOAT is a combination of IAT and OAT with nitrites that actually existed prior to the development of OAT. The generally recommended replacement interval is 3 years or 150,000 miles. (Photo Courtesy Jim Halderman)

HOAT is used in newer Ford, Chrysler, and Mercedes vehicles. It uses the best aspects of both IAT and OAT, making HOAT a very protective, long-life coolant. HOAT coolants typically mix an OAT with a traditional inhibitor, such as silicate or phosphate. HOAT can be dyed red, pink, yellow, or blue.

HOAT types are as follows:

Volkswagen or Audi: Pink; contains some silicates and an organic acid; phosphate free

Mercedes: Yellow; contains low amounts of silicate; phosphate free

Ford: Yellow; contains low silicate; phosphate free; dyed yellow for identification

Ford yellow HOAT (shown) contains low silicate, no phosphate, and is dyed yellow for identification.

Honda: Blue; contains a special coolant with just one organic acid

European or Korean: Blue; contains low silicates; phosphate free

Asian: Red; contains no silicates; has some phosphate

Phosphate Hybrid Organic Acid Technology

Phosphate hybrid organic acid technology (PHOAT) was developed for Mazda-based Fords of 2008 and later. It is ethylene glycol based and available in a 55-percent coolant and 45-percent water premix. The premix containers make sure that the water used meets specifications. The use of PHOAT coolant in Ford Mazda engines is required to be assured of proper protection of the internal coolant passages in the engine.

Phosphate hybrid organic acid technology (PHOAT) was developed for Mazda-based Fords in 2008 and later, such as the Mazda FL-22. It is ethylene glycol based. Ford Mazda engines required the use of PHOAT coolant to be assured of proper protection of the internal coolant passages. It is also only available in premix containers to make sure that the water used meets specifications. (Photo Courtesy Jim Halderman)

PHOAT Properties

Concentration: 55 percent

Boiling point (with 15-psi pressure cap): 270°F (132°C)

Freezing point: -47°F (-44°C)

Color: Dark green

Embittered (made to taste bitter so animals will not drink it)

North American green antifreeze was the original “universal” formula, and it was the coolant used until the introduction of extended-life coolants. The fast-acting silicate and phosphate corrosion inhibitors provided quick protection for bare iron and aluminum surfaces and had a proven track record of providing trouble-free service in virtually any vehicle application (domestic, Asian, or European), assuming the chemistry is correct. OAT coolants should not be used in a vehicle that specifies the use of a hybrid OAT coolant. Always check the vehicle’s owner’s manual. Yet, the short-lived nature of the corrosion inhibitors means this type of coolant should be changed every 2 to 3 years or 30,000 miles.

Universal Coolant

Universal coolant is usually a HOAT antifreeze. It is extended life, low-silicate, phosphate-free coolant. It can be used in many vehicles. However, it cannot be use in Mazda vehicles and cannot meet the needs for engines requiring a silicate-free formula.

Antifreeze Components

Coolant is made up of an antifreeze component and a series of additives. Irrespective of the type of coolant and its color, the only difference between all the original equipment coolants is in the additives. This means about 97 percent of all coolants are the same; the only difference is in the additive package and color used to help identify the coolant.

Traditional Inhibitors

There were two major corrosion inhibitors traditionally used in vehicles: silicates and phosphates. American-made vehicles used both silicates and phosphates. European makes contain silicates and other inhibitors but no phosphates. Japanese vehicles traditionally use phosphates and other inhibitors, but no silicates.

Additives

All automotive antifreeze formulations, including the newer OAT and HOAT antifreezes, are environmentally hazardous because of the blend of additives, including lubricants, buffers, and corrosion inhibitors. Most commercial antifreeze formulations include corrosion-inhibiting compounds and a colored dye (commonly a fluorescent green, red, orange, yellow, or blue) to aid in identification.

Additives make up about 5 percent of the coolant. These additives are proprietary, so OEM safety data sheets (SDS) list only those compounds that are considered to be significant safety hazards when used in accordance with the manufacturer’s recommendations. Common additives include sodium silicate, disodium phosphate, sodium molybdate, sodium borate, denatonium benzoate, and dextrin (hydroxyethyl starch).

Disodium fluorescein dyes are added to antifreeze to help trace the source of leaks, and it is as an identifier because some formulations are incompatible. Automotive antifreeze has a characteristic odor due to the addition of the corrosion inhibitor tolytriazole.

Waterless Glycerol-Based Coolant

There are glycerol-based coolants that do not require water. Glycerol is nontoxic, noncorrosive, and withstands relatively high temperatures. It was used as an antifreeze for automotive applications due to its low freezing point before it was replaced by ethylene glycol.

Like ethylene glycol and propylene glycol, glycerol is a non-ionic kosmotrope that forms strong hydrogen bonds with water molecules, competing with water for the hydrogen bonds. This interrupts the formation of ice unless the temperature is significantly low. Glycerol is mandated for use as an antifreeze in many sprinkler systems.

Evans Heavy Duty waterless coolant is the original lifetime waterless coolant that does not require replacement. It is recommended for racing engines run on tracks or in series where there is a ban on ethylene glycol. (Photo Courtesy Evans Coolant)

There are very few waterless coolants that use glycerol.

Evans Coolant

Water provides very superior heat transfer, but only if it remains in its liquid state. Evans waterless coolant does its job of removing heat well past the failure point of 50-50 coolant. Vapor pressure is also reduced with Evans compared to 50-50 coolant.

Evans makes several different waterless coolants: High Performance, Powersports, Heavy Duty, and Non-Propylene Glycol (NPG). Its products can be used in high-performance street vehicles and work best with high-flow cooling systems. In most cases, the stock cooling system configuration is sufficient, and there is no need to change the thermostat or radiator pressure cap. Operation system modifications, such as increasing coolant flow rate, can be done to optimize Evans’s performance.

At 375°F, Evans’ boiling point is more than 100 degrees higher than water-based coolant. Ethylene glycol is around 275°F and water’s boiling point is 212°F. (Chart Courtesy Evans)

Questions and Answers with Evans Engineer Mike Tourville

Q What are the advantages of Evans waterless coolants?

A Evans contains no water, has a boiling point of 375°F, and freezes at -40°F. This means no vapor formation, no vapor pressure, and no boil over. Evans maintains its liquid state, and with constant liquid-to-metal contact, efficient heat transfer continues even under higher temperatures. Evans’s lower operating pressure reduces stress on hoses, seals, and gaskets. The absence of water also means no corrosion and electrolysis.

Q How does Evans waterless coolant function differently in the cooling system?

A Evans avoids the boiling condition at stressed temperatures, which is the weakness of water. Evans waterless coolants remain liquid, maintain good heat transfer, keep engine component temperatures safe, reduce pressure, and avoid rust and galvanic erosion.

Q How do Evans waterless coolants control engine metal temperatures as compared to water-based coolants?

A Water-based coolant boils at a temperature only slightly higher than the operating temperature of the coolant. Localized boiling releases water vapor that can only condense into coolant that is colder than the boiling point of water. Vapor that doesn’t condense occupies a volume that displaces liquid coolant. Hot engine metal, insulated by water vapor, becomes an engine hot spot that can cause pre-ignition and detonation. Evans’s high boiling point means it will not turn to vapor.

Q Will Evans coolant lower the operating temperature of my engine?

A Vehicles running under normal operating conditions should show either no change or a slight increase in temperature, but that will depend on the cooling system configuration and driving conditions. Certain systems that use incompatible components, have an existing problem, or are poorly designed could run hotter. The ability to lower the operating temperature depends on multiple factors—primarily coolant flow volume and airflow temperature. For example, multi-pass radiators will result in higher temperatures due to decreased coolant flow volume versus large-tube multirow radiators that improve coolant flow. Different thermostats may increase flow volume because of less restriction.

Q Why does my engine run hotter after switching to Evans waterless coolants?

A A system that is highly optimized for water (with restrictive flow and high-pressure differentials) can cause slower circulation with Evans waterless coolants. Evans won’t boil, but if it is held longer in the engine, it can pick up more heat. The coolant temperature is what your gauge reads. If the rest of the system is capable and compatible, Evans waterless coolants can process more heat out of the engine, and the engine component temps are actually improved and stabilized.

Q Why do museums and collectors such as Jay Leno use Evans?

A They use Evans for corrosion protection in older vehicles that have dissimilar metals in the system that sit for long periods of time. And of course, they use it for temperature control under the hot Southern California climate and traffic conditions.

Q How does Evans prevent water pump cavitation?

A Evans waterless coolant inhibits vapor development in the pump over a broad range of temperatures. With Evans waterless coolant, the suction side of the coolant pump is never at a low enough pressure to flash vaporize the coolant. The pump never gets vapor-bound and can continue to pump coolant. No vapor bubbles are formed to collapse against the metal and cause cavitation erosion damage to the pump.

Q How do I install Evans waterless coolant?

A The conversion process is not complicated, but it should be done thoroughly and according to written instructions, along with instructional videos on our website: evanscooling.com.

1. Drain all old water-based coolant from radiator, block, and heater core if accessible.

2. Use high-volume air to force out remaining coolant.

3. Fill with Evans Prep Fluid (waterless flush) and run for 15 minutes to circulate.

4. Allow to cool and drain the Prep Fluid in the same manner as the old water-based coolant.

5. Fill with Evans waterless coolant and run for 15 minutes to circulate.

6. Test for water content to confirm there is less than 5 percent water. Water content can be measured with a refractometer or a sample can be sent to Evans for testing.

Q How do I get all the water out? What if some water is left?

A Excess residual water can bring back the symptoms that Evans is intended to eliminate: the effects of vapor and corrosion. For best results, maintain a water percentage below 5 percent. If a loss of coolant occurs from a leak, requiring an emergency top off, water can be used and will mix with the Evans. The additional water will compromise the benefits of Evans, and it is recommended to reinstall Evans within a few weeks.

Q How much Evans Prep Fluid do I need to use?

A If you cannot fully drain the system, open the lower radiator hose, block drain (if accessible), and heater core. Allow them to empty and force high-volume air to purge the remaining coolant. Fill with Evans Prep Fluid and run the vehicle to circulate and drain again. This would require approximately 75 percent of the system volume of Prep. Alternately, smaller quantities of Prep can be used to flush through a component or plumbing.

Q What happens if I have water in my cooling system after installing Evans?

A A water content higher than 5 percent will lower the boiling point and may reduce the corrosion protection. If a water content exceeds 5 percent, drain a portion from the system and add back new Evans waterless coolant until it is below 5 percent.

Q If I have a leak and Evans is not immediately available what can I safely add?

A The likelihood of coolant loss and the need for topping up are greatly reduced with Evans. In the event a leak occurs and Evans is not available, water or water-based coolant may be used. The cooling system will function but the boil-over and corrosion protection of Evans waterless coolant will be reduced. As a temporary measure, stop leak products may be used. Current approved dry-type stop leaks are Bars Leak tablet part #HDC, GM Cooling system Tabs, Aluma Seal, and Copper Seal. Liquid stop leak products compatible with Evans are: Bars Leak part number 1186 and K-Seal part number ST5501.

Q Do I need to change my radiator cap when using Evans?

A No, a different radiator pressure cap is not required. Evans waterless coolant expands slightly as it warms, creating pressure of 3 to 5 psi, and the existing cap does not need to be changed.

Q What other system modifications are recommended to optimize Evans waterless coolant?

A In most cases, no modifications are needed; however, the higher coolant flow rate the better. This can include increasing pump output and lessening restrictions such as the thermostat. No need to change the pressure cap, as the point at which the cap will vent is less important, as Evans waterless coolant does not require pressure to keep it in the system. Contact Evans’s tech support team for recommendations for your system at 888-990-2665.

Q Can I use it with a multi-pass radiator?