Antifreeze / Definitions

Antifreeze / Coolant Description:
Antifreeze/coolant serves four purposes in a vehicle cooling system.

1.     To lower the freezing point below 32º F / 0º C. (To help prevent freeze up)
2.      To raise the boiling point above 212º F / 100º C. (To help prevent boil over)
3.      To protect the cooling system against corrosion.
4.      To lubricate water pump seals.



Types of Coolant / Antifreeze:

In today’s day and age, there are many variations of coolant/antifreeze and can be quite confusing. But they are all based on ethylene glycol (EG) or propylene glycol (PG). From this, six groups come out. Colors vary from types, to the different manufacturers.

1. Inorganic Acid Technology (IAT) – This is the old typical green antifreeze/coolant that contained Silicates, Phosphates and/or Borates. The average life of IAT was from: 2 years/30,000 miles to about 3 years/36,000miles (dependent on manufacturer’s interval specs).
2. Organic Acid Technology (OAT) – This variation does not contain silicates or phosphates. A version of this is called Dex-Cool that has been used in GM cars since 1996, and Volkswagen/Audi uses a similar version called G12, G12+ and G12++ of this antifreeze/coolant. They contain 2-EHA and /or Sebacate for corrosion protection. This is a long life coolant with an interval of around 5 years/50,000 miles (dependent on manufacturer’s interval specs).
3. Hybrid Organic Acid Technology (HOAT) – Is a combination of organic acid technology (OAT) with a low dose of silicates or phosphates. Most antifreeze/coolant is of this variation. This is a long life coolant with an interval of around 5 years/50,000 miles (dependent on manufacturer’s interval specs).
4. Nitrited Organic Acid Technology (NOAT) – Is an organic acid technology (OAT) that has no silicates or phosphates. It contains nitrates and/or molybdenum as part of their inhibitor package. This coolant is an extended life coolant and does not require supplements. This extended life coolant has a service interval of around 8 years / 750,000 miles (dependent on manufacturer’s interval specs).
5. Nitrited Molybdate Organic Technology (NMOAT) – This coolant is similar to NOAT that has nitrates, but also has Molybdate for diesel wet sleeve liner protection.
6. Poly Organic Acid Technology (POAT) – This a long life coolant that is propylene glycol based, organic acid technology. Currently Amsoil is the only manufacturer for this coolant.




Antifreeze vs. Coolant

Antifreeze – Is undiluted and must mixed to a 50/50 antifreeze to water ratio. Distilled water should be used to dilute antifreeze. Use the correct ratio recommended by vehicle manufacturer. As a note, running straight antifreeze in an engine, will result in a hotter running engine. Antifreeze does not have the heat transferring abilities as water.


Coolant – Is pre-diluted and ready to use. Coolant does not require water to be added


SCA (Supplemental Coolant Additive) / DCA (Diesel Coolant Additive) – Because additives in conventional (IAT) and hybrid organic acid (HOAT) coolants are consumed during the vehicle’s operation, they must be refortified with supplemental coolant additives (SCA/DCA) in order to maintain effective corrosion protection. On the other hand, OAT and NOAT coolants do not require SCAs. Also note that the inhibitor package does not determine the level of freeze or boil over protection; the inhibitor is responsible for corrosion protection only.





⇒Most antifreeze / coolants are dangerous to humans and animals if ingested. They can cause severe injury or death. Use caution with children and animals since most coolants are sweet tasting.
⇒Dispose of used antifreeze / coolant to proper recycling center.
⇒Wear personal protective equipment.
⇒Use caution when working with hot coolant.





Acidic (pH) – Liquid having a pH rating of 1 – 6 on the pH scale (sour). Acids fall in this scale.
Alkaline (pH) – Liquid having a pH rating of 8 – 14 on the pH scale (sweet). Caustics fall in this scale.
Antifreeze – This type is 100% antifreeze and has to be diluted with water to achieve desired freeze point. Running 100% antifreeze is not advisable.
Basic (pH) – see Alkaline.
Benzoate – A corrosion inhibitor that is the main inhibitor in HOAT antifreeze/coolant and G-05 antifreeze/coolant.
Benzotriazole (BZT) – An inhibitor that protects brass and copper against corrosion.
Boiling Point – The temperature that a liquid changes from liquid to gas.
Borate – A chemical used in antifreeze/coolant SCAs to maintain the pH as it ages. It is a pH buffer.
Carboxylates – Organic acid anti rust inhibitors.
Caustic – A solution that has a pH of 12 to 14 pH.
Cavitation – The formation of bubbles and the immediate implosion of them. This produces a shock wave that causes pitting and erosion where it is occurring inside the cooling system.
Coolant – This type comes pre-mixed with water in a 50/50 mix. It is ready to be used and should not be diluted with water.
Coolant System Flush – A chemical or water cleaning of a cooling system to remove old antifreeze/coolant and particles from a cooling system.
Colligative Agent – Antifreeze/coolant is a colligative agent that raises and lowers the boiling point and freezing point in a cooling system.
Convective Heat Transfer – Heat transfer thru fluid movement in liquid or gas. Cooling systems work in this manner.
Corrosion – A destructive reaction of a metal with another material, e.g. oxygen, water, chemical (either acidic or alkaline).
Corrosive – A chemical (liquid, solid, or gas) that can cause destructive damage to body tissues, metals and other materials.
Deionized water (DI) – see Distilled water.
Denatonium – A bitter tasting agent added to antifreeze/coolant to make it bitter.
Distilled water – Water that has had minerals ions removed. In a cooling system, hard water contains calcium and magnesium that will form deposits in a cooling system.
Electrolysis – A chemical process that induces the transfer of metal by way of electrical current flow.
Ethylene Glycol – A colorless, odorless, syrupy, sweet alcohol that is toxic
Hybrid Inorganic Acid Technology – Antifreeze/coolant that is either ethylene glycol or propylene glycol that has a low dose of silicates or phosphates added.
Freezing Point – The temperature that a liquid changes from liquid to solid.
Galvanic Corrosion – This happens when dissimilar metals are in electrical contact. The Anode (+) metal will corrode faster than the Cathode (-) metal.
Glycerol – It was used as antifreeze/coolant before it was replaced by ethylene glycol.
Hybrid Organic Acid Technology (HOAT) – Antifreeze/coolant that is either ethylene glycol or propylene glycol that has a low dose of either silicates or phosphates.
Hydrometer – Measures the density of the coolant to the density of water. Reads freezing point and boiling point of antifreeze/coolant.
Inorganic Acid Technology (IAT) – Antifreeze/coolant that is either ethylene glycol or propylene glycol that has silicates and phosphates added (traditional green).
Ion – Is an atom or a molecule in which the total number of electrons is not equal to the number of protons, giving it a net positive or negative charge.
Molybdate – An additive to prevent cylinder liner cavitation.
Neutral – Having a pH of 7. The middle of the pH scale.
Nitrate – An anti-corrosion additive in preventing rust.
Nitrite – An additive to prevent cylinder liner cavitation.
pH – Potential for hydrogen.
pH Scale – A scale of 1-14, 1-6 being acidic, 8-14 being alkaline, and 7 being neutral.
Phosphates – An inorganic chemical that insulates the metal in a cooling system against corrosion.
Plasticizer – A substance that softens certain plastics, silicones, and nylons.
Propylene Glycol – Similar to Ethylene glycol but not as sweet tasting, but is not as toxic to environment.
Organic Acid Technology – Antifreeze/coolant that is either ethylene glycol or propylene glycol that has no silicates and phosphates added (Dex-cool and VW/Audi coolants).
Refractometer – An instrument that measures the refractive index of a liquid.
Reserve Alkalinity – A coolants ability to neutralize acid.
Sebacate – An organic acid added to coolant for corrosion protection.
Silicates/Silicone – An additive to antifreeze/coolant that reacts with the metals in a cooling system to protect against corrosion, particularly with aluminum. It is based from sand and has deemed abrasive to coolant systems and certain water pump seals.
Sodium Hydroxide – An additive to help maintain pH balance.
Sodium Silicate – Used in block sealers, head gasket sealers, and radiator sealers. Called liquid glass that forms a powerful sealant.
Surface Tension – Is the property of the surface of a liquid that allows it to resist an external force.
Surfactant – Is a compound that lowers the surface tension of antifreeze/coolant and allows better heat transfer. Used in additives designed to help lower cooling system temps.
Triazole / Thiazoles – An additive for corrosion protection, particularly with brass and copper.
Tolyltriazole (TTZ) – An inhibitor that protects brass and copper against corrosion.
2-EHA (2-ethylhexanoic acid) – An organic acid added to coolant for corrosion protection. It is a plasticizer that can damage silicone rubber gaskets and certain nylon gaskets.





ASTM – American Society of Testing and Materials
ATC – Automatic Temperature Compensated
DCA – Diesel Coolant Additive
DI – deionization
DMM – Digital Multi Meter
DVOM – Digital Volt Ohm Meter
EG – Ethylene Glycol
ELC – Extended Life Coolant
ESI – Extended Service Interval
HOAT – Hybrid Inorganic Acid Technology
IAT – Inorganic Acid technology
LLC – Long Life Coolant
NORA – National Oil Recyclers Association 
NPG – Non-Aqueous Propylene Glycol
OAT – Organic Acid Technology
PG – Propylene Glycol
pH – potential for hydrogen
SCA – supplemental coolant additive





Antifreeze/Coolant Pros and Cons:


⇒Lowers freeze point
⇒Raises boiling point
⇒Lubricates water pump
⇒Prevents corrosion


⇒Does not have a good heat transfer compared to water
⇒Harmful to environment if improperly disposed
⇒Mixing of two different antifreeze/coolants can damage a cooling system
⇒Antifreeze/coolant not replaced at service intervals can damage a cooling system
⇒Improper antifreeze to water ratio mix can affect desired protection and will affect corrosion protection, freeze point and boiling point.


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