Coolant for the car: finding the right one quickly and easily

In the automotive sector, customers often receive very good overviews of the right engine oil, transmission oil or brake fluid. However, when it comes to coolant, many do not come across any information that is all that helpful. Yet choosing the right coolant is just as relevant to the life of a car as the right engine oil.

What is the biggest problem in choosing the right coolant?

In a nutshell, the lack of an international standard for coolants is the big issue. Compared to engine oils, where a suitable oil can be determined based on its manufacturer-specific release or specification, coolant lacks such transparency.

Customers are inundated with a wide variety of colors, additives and special benefits. The primary question for every motorist is whether or not the coolant is at all suitable for his or her own vehicle. Once this hurdle has been overcome, a comparison based on the manufacturer’s own advantages would only be of interest. Returning to the search for the right coolant and the required quantity, clarity should first be provided as to what tasks a radiator antifreeze actually performs, what it is made of and how it is best mixed. These questions are briefly and concisely addressed below.


Task of the coolant

On the one hand, the coolant is responsible for lowering the freezing point of the entire liquid in the cooling system and thus preventing the radiator and all pipes from freezing. The real strength of a coolant therefore unfolds during the winter period, when at sub-zero temperatures the fluids threaten to freeze.


Requirements for a good coolant

A good coolant can quite simply lower the freezing point of water, but it must not corrode with the metals in the cooling system, attack rubber seals, or drive other signs of wear. So to be convincing in overall use, a good coolant must meet certain requirements:

  • Preventing deposits in the cooling system
  • Prevent foam formation
  • Improving corrosion and heat protection
  • Compatible with the metals and rubbers in the cooling system

Composition of a cooling liquid

The chemical components around monoethylene glycol (MEG), ethylene glycol (EG) or monopropylene glycol (MPG) are used as the basis of every coolant. Based on this base, the relevant additives are added to give the coolant the special property.

These additives include:

  • Corrosion inhibitors –So that the corrosion process is limited
  • Foam preventerTo prevent foaming during use
  • Stabilizers For consistent performance at extreme temperaturesn
  • Cavitation InhibitorsPrevents the formation of steam bubbles and thus pressure

The result of the basic components mixed with the additives is the coolant concentrate. This is ready for use in the cooling systems intended for this purpose.

OAT, IAT and HOAT coolant

As with engine technology, the individual coolants have also changed. Abbreviations such as OAT, IAT and HOAT are usually used to typify the type of coolant. They give an indication of which organic or inorganic acid is contained in the coolant whether they are miscible with each other.

IAT – The abbreviation IAT stands for “Inorganic Acid Technology.” It refers to the fact that inorganic acids are contained in the coolant. One such inorganic acid is silicate. Silicate was used at the beginning of coolant production. Concentrates with this acid base can be mixed with each other, but not arbitrarily with all OAT coolants (see the following table). For example, an IAT coolant is the G11 or G48 standard.

OAT – The abbreviation OAT stands for “Organic Acid Technology”. Here the reference to the use of an organic acid applies. In this case, silicate was not used. The first coolants with the OAT property were not miscible with the IAT coolants. However, further developments made it possible to mix OAT and IAT coolants. You can see which ones in the following table. An OAT coolant is for example the G12, G12+ or G30 standard.

HOAT – The abbreviation HOAT stands for a hybrid technology of OAT coolants. It stands for “Hybrid Organic Acid Technology”. The HOAT property combines the advantages of OAT and IAT coolants. Hereby silicate is used as corrosion inhibitor and all other additives are used by means of organic acids. This also gives them the property that they are miscible with all other coolant standards (thus also silicate-containing)! The HOAT coolants include the G12++, G13 and G40 standards.

The correct coolant (concentrate) mixture with water

The coolant concentrate should always be mixed with clear water. Generally, tap water can also be used for this purpose. However, throughout Germany, the lime content, which accelerates the wear process, is different in every part of the country. For this reason, it is always recommended to use distilled water. This prevents faster wear due to residues in the tap water.

According to the manufacturers, the concentrate should always be mixed in a ratio of 1:1. Accordingly, 1 L of coolant concentrate is mixed with 1 L of distilled water. This mixing ratio mostly guarantees optimal protection at up to -36 degrees.

Of course, the countries in central Europe do not reach such temperatures. For this reason, a higher proportion of water could also be used.

But what is the maximum mixing ratio that can be achieved?

At a ratio of 1 L of coolant concentrate and 2 L of water, the guaranteed protection would drop to -20 degrees. Overall, the rule should always be followed that there is never more than 60% and never less than 33% coolant concentrate in the cooling system.

The color of a coolant

For consumers, it would be a simple matter if the color were representative of the coolant’s release. If, for example, a red coolant was in accordance with VW G12 standards and the purple color was exclusively for VW G13. Unfortunately, this is not the case. Quite the opposite!

Each coolant manufacturer uses its own color combinations for its radiator antifreeze. The reason is very simple: The color is not a central indicator for the composition of the coolant. It can therefore happen that you find two suitable coolants for your car, which have different colors despite matching approval. Especially when mixing the different colors, this results in even more unsightly colors that none of us wants to see in our cooling system.

Therefore, when buying a coolant, you should never decide on the color alone, but always on the required coolant release. In the following, we show you examples of which colors different manufacturers use despite the same release.

Kühlflüssigkeit Farbe

Buy coolant – where to find the best price?

If you know exactly what coolant your car needs, you have many options for buying it directly. On the one hand, the coolant can be bought at workshops, gas stations or just online. At workshops, you can mostly get the original coolants from the manufacturers. This has the advantage that the fluids are used, which are also used from the factory. One disadvantage is mostly the price, since the workshops usually sell the concentrates at higher prices than they are available on the Internet.

Those who buy their coolant on the Internet can usually obtain the products at lower prices. There are many online stores or marketplaces such as Amazon and eBay for this purpose. Although shipping costs are incurred there, the products still remain cheaper than at garages or service stations.

The situation with service stations is the same as with garages. The advantage is direct availability, but this is also paid for with a higher price. Consequently, it is advisable to buy coolant before it is needed in an emergency. If you have your workshop appointment firmly in mind, you can also buy your coolant on the Internet beforehand and save money. The same applies to engine oils and automatic transmission oil.

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