A Complete Guide to Antifreeze

In this Complete Guide to Antifreeze, we’ll explore what it is, how it’s made, its uses, hazards, benefits and specifications. You’ll also find further information and reading material in the links at the bottom of this page.

What Is Antifreeze?

Antifreeze is an additive which decreases the freezing point and increases the boiling point of water-based liquids. This means that the liquid won’t freeze or boil as quickly as it would without the antifreeze, providing a wider range of temperatures at which the liquid can perform. Its most common use is in internal combustion engines where the antifreeze helps to regulate the engine during extreme temperatures – either hot or cold. 

Before antifreeze, water alone was used to cool engines. However, water has a limited 100°C liquid range and expands upon freezing. Antifreeze was developed to solve the issues of water as a heat transfer liquid.

Antifreeze has highly beneficial properties, including:

  • High boiling point
  • Low freezing point
  • Stability over a range of temperatures
  • High specific heat and thermal conductivity
  • Low viscosity
  • Chemically inert

The word ‘antifreeze’ is commonly applied both to its concentrated form and to the water-diluted solution. 

Different Types of Antifreeze

You may know that antifreeze comes in a variety of colours, from red and blue to green and orange, created by adding dye. Why? Mainly for historical reasons – the different colours reflected either where the product was made, the brand that made it, or the type of corrosion-preventing chemical it contained. 

One of the main uses of antifreeze is in internal combustion enginesFor example, older antifreezes used inorganic additive technology and were either blue or green. As technology progressed, antifreezes became silicate-free and used organic acid technology. These extended-life antifreezes tended to be orange. These days, the colour doesn’t reflect the product itself so it’s not easy to know which chemicals the antifreeze contains just by seeing whether it’s blue, green, yellow or orange.

Is Antifreeze the Same as Coolant?

When referring to the liquid in an engine’s cooling system, antifreeze and coolant are words that can be used interchangeably because they both describe the liquid that helps the engine run at the right temperature.

The difference between antifreeze and coolant is that an engine needs to be cooled to the right temperature 365 days a year no matter the weather, meaning that an engine needs a coolant at all times. When it’s cold, the coolant’s antifreeze properties should prevent the liquid from freezing.

How Is Antifreeze Made?

There are two main ways to make commercial antifreeze, either by using ethylene glycol or propylene glycol. These formulations can be sold as concentrate or as a dilution with water. A 50%:50% dilution, which gives a freezing point of approximately -37°C (-34.6°F), is typically used in the UK but in warmer or colder climates, weaker or stronger dilutions are used as necessary.

Antifreeze may also contain other additives such as phosphates and silicates which help protect against corrosion and growth of biological matter. The benefit of this is that if corrosion or biological matter were allowed to build up, they could limit the effect of the antifreeze and cause damage.

Ethylene Glycol

Ethylene glycol is the most common compound used in the commercial manufacture of antifreeze. Brought into use in the mid-1920s, it was sold as a “permanent antifreeze” because its liquid temperature range was beneficial both during the summer and the winter. Additionally, because it is an inert compound it doesn’t react with metal and therefore isn’t corrosive.

It is an odourless, colourless, and sweet-tasting liquid listed as a toxic chemical requiring care in handling and disposal. Ethylene glycol itself is made from ethylene (ethene) via the intermediate ethylene oxide which reacts with water to produce ethylene glycol:

C2H4O + H2O → HO−CH2CH2−OH

Ethylene glycol is the key additive in most antifreezes

Propylene Glycol

Propylene glycol is a less toxic, more environmentally-friendly alternative to ethylene glycol and is therefore used as an antifreeze when you would not be able to use ethylene glycol, for example in food processing systems or domestic water pipes. 

It is a viscous, colourless liquid which is almost odourless but, like ethylene glycol, it has a slightly sweet taste. Propylene glycol can be manufactured from glycerol, a byproduct from the production of biodiesel, when it is being used for industrial uses such as making antifreeze rather than food-grade use.

Although its physical properties are less desirable than ethylene glycol, propylene glycol is used in applications where toxicity could be a concern as it is generally recognised as safe for use in food or food processing applications. In this case, propylene glycol would be produced from propylene oxide, either through a non-catalytic high-temperature process or a catalytic method in the presence of ion exchange resin.

Other Antifreezes

Glycerol was once used as an antifreeze before being replaced by ethylene glycol. It is non-toxic, tolerates high temperatures relative to ethylene glycol and propylene glycol, and is non-corrosive. 

Propylene glycol methyl ether is a clear, colourless organic solvent used as an antifreeze in diesel engines. 

Uses of Antifreeze

Antifreeze has many different uses, the most common of which is in automotive engines. In general, antifreeze is used as a heat transfer fluid to protect engines – and other products as we’ll see below – from both the cold and the heat.

Automotive and Internal Combustion Engines

Most automotive engines are water-cooled to remove waste heat, with the water being a mixture of antifreeze and water. As the external temperature changes, antifreeze is pumped through the engine to maintain it at a uniform temperature. 

The most well-known use of antifreeze is as a coolant in internal combustion enginesIt also protects the engine from internal scale build-up, lubricates any moving parts it comes into contact with, and helps to get your car to its optimum operating temperature as quickly as possible which reduces air pollution. Corrosion inhibitors are also added to antifreeze. These inhibitors help protect vehicles’ radiators which are often made of incompatible metals such as aluminium, cast iron, and copper. 

HVAC and Solar Water Heating Systems

Heating, ventilation and air conditioning (HVAC) systems are an integral part of modern residences, office buildings and hospitals, as well as submarines and ships. Antifreeze can be used in HVAC systems to help prevent pipes from freezing, bursting and causing damage. It also reduces the risk of scale build-up and corrosion. Typically, glycol is the agent used in these systems as it is non-toxic.

With the use of solar energy on the increase, it’s important to maintain these systems properly. Antifreeze is used in solar water heating systems as a heat transfer fluid, providing protection from freezing and damage to the system in colder climates. 

Antifreeze is used in HVAC systems as a coolant to regulate the system's temperatureBiological Antifreezes

Antifreeze is also found in nature. As living cells contain a lot of water, they’re also in danger of turning to ice and fracturing in freezing conditions. Certain animals, insects, and plants are able to produce antifreeze proteins (AFPs) which prevent the formation of ice in their systems. These antifreeze compounds bind themselves to ice crystals and prevent fatal ice growth, meaning that the organism can operate at temperatures below the freezing point of water. These AFPs have a range of potential medical and commercial uses, such as in enhancing the preservation of transplant organs, preventing frostbite, and making crops more resistant to the cold.

Benefits of Antifreeze

As we’ve seen, antifreeze has a range of benefits, including:

  • High boiling point
  • Low freezing point
  • Stability over a range of temperatures
  • High specific heat and thermal conductivity and improved heat transfer
  • Low viscosity
  • Chemically inert
  • Reduction in repairs to thermostats, radiators, and water pumps
  • Save time and money in maintenance
  • Anti-corrosion protection
  • Compatibility with rubber and plastics

Hazards Of Antifreeze

Propylene glycol is an ingredient in some foods and cosmetics and isn’t considered harmful in small amounts. However, while sweet-tasting, ethylene glycol is a toxic chemical and ethylene glycol poisoning can occur when just a small amount is ingested. Breathing its vapours may also cause eye and respiratory irritation.

Symptoms of Antifreeze Poisoning

It’s common for antifreeze poisoning to happen gradually, depending on how much you have ingested. As your body absorbs antifreeze, it is converted into other toxic substances, like glycolic acid, acetone, and formaldehyde.

Early symptoms of antifreeze poisoning include a feeling of drunkenness, headache, fatigue, nausea, and vomiting. After that, you may experience rapid breathing, a fast heartbeat, and convulsions. Antifreeze can inhibit organ and nervous system function, leading to severe damage. You may lose consciousness and fall into a coma. Antifreeze poisoning can be fatal.

Antifreeze Poisoning & Animals

Antifreeze can be lethal to animals. As it’s sweet-tasting, it isn’t uncommon for an animal to drink antifreeze that has dripped from a vehicle’s cooling system. If the animal isn’t treated within a few hours, the antifreeze can cause severe kidney damage and can kill within 24 hours.

Antifreeze & the Environment

All automotive antifreeze formulations are considered to be environmentally hazardous because of the blend of additives they contain, including lubricants, buffers and corrosion inhibitors.

Antifreeze Specification

Antifreeze Blue – Ready to Use

AppearanceClear blue liquid, free from particles
Density @ 20°C1.055 – 1.075g/ml
Monoethylene Glycol content47 – 50% w/w
Conforms to BS 6580 2010
Freezing Point (as supplied)<-35°C

Non-Toxic Antifreeze

AppearanceClear, colourless liquid
Meets ASTM D3306 Type II, ASTM D 4985, SAE J 1034, BS 6580 (1992), AFNOR NF R15-601
S.G. @ 15°C (ASTM D 4052)1.030 – 1.065g/ml
Equilibrium reflux boiling point°C (ASTM D 1120)>152°C
pH (50% vol)7.5 – 9.5
Freezing Point 50% vol dilution with water-34°C
Freezing Point 33% vol dilution with water-15°C

Antifreeze Material Safety Data Sheet (MSDS)

Antifreeze material safety data sheets list the compounds considered significant safety hazards when used according to recommendations, including sodium silicate, sodium borate, and denatonium benzoate.

You can find the material safety data sheets for antifreezes below. These MSDSs list the potential hazards (including health, fire, reactivity and environmental hazards) of antifreeze and how to use or work with it safely.

Where To Buy Antifreeze

Antifreeze is commonly available for consumer and business purchase.

Consumers Buying Antifreeze

As a consumer, you can buy antifreeze from many supermarkets, hardware stores, and online retailers. The benefits are ease and cost – you can simply include the product in your weekly shop.

Businesses Buying Antifreeze

If you are a business looking to buy antifreeze on a large scale, you will probably need to purchase from recognised, reputable chemical company. Why?

  • A chemical manufacturer will probably supply a range of antifreeze
  • An established company has a proven track record 
  • You’ll get advice on the best type of antifreeze for your needs
  • You should get free technical support 
  • Chemical companies often hold quality accreditations such as ISO 9001
  • Reliable couriers mean your order will be delivered on time and in full
  • You can get certificates of conformity and analysis 

You can also purchase antifreeze from online retailers such as Amazon and eBay. If you choose to do this, we recommend checking the sellers in detail. You’ll probably find that they aren’t of as such good repute as established chemical companies. For example, they generally won’t have the same high quality standards or accreditations.

Buying antifreeze online also means there’s another party in your supply chain, which can get complicated. It may be difficult to get a VAT receipt, and you probably won’t get the same standard of after-sales support.


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