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AdBlue - how does it work and should you be afraid of it?

AdBlue is supposed to protect the environment, but some drivers don't like having to take care of it and also incur additional costs. In this article, we explain what AdBlue is and how exactly it works.

AdBlue is a brand name for a diesel exhaust fluid (DEF) used in selective catalytic reduction (SCR) systems to reduce nitrogen oxide (NOx) emissions from diesel engines. It's a clear liquid composed of a mixture of urea and deionised water. AdBlue is not a fuel additive; rather, it's injected into the exhaust stream to facilitate a chemical reaction that converts harmful nitrogen oxides into harmless nitrogen and water vapor.

Simply put, it is a fluid that is designed to neutralise environmentally harmful substances in diesel cars. However, it is not a fuel additive , but a fluid that mixes with the exhaust gases outside the engine.

In the SCR technology, AdBlue is directed under high pressure to the exhaust gas stream in the catalyst, where the reduction of nitrogen oxides harmful to the atmosphere into nitrogen and water takes place.

The whole process is safe, and AdBlue is not harmful to humans or the environment. Interestingly, the substance is not blue at all (as the name suggests), but colorless. Its use is regulated by the requirement of ecology and applicable law, under which new cars are approved. 

adblue icon

How does AdBlue work?

AdBlue fluid placed in a separate tank under appropriate pressure goes to the SCR ( Selective Catalytic Reduction)  catalyst , which is located in the exhaust system. The high temperature prevailing there causes the release of ammonia from the urea in the solution, which reacts with nitric oxide. As a result, instead of exhaust gases, water vapor and volatile nitrogen are released, completely harmless to the environment. The same properties apply to AdBlue.

When and why was AdBlue used?

The world heard about AdBlue massively after the introduction of the Euro 6 emission reduction standard. From September 1, 2014, all new diesel-powered trucks and passenger cars must comply with it. Euro 6 forced manufacturers to reduce the content of nitrogen oxides in exhaust gases by as much as 80% compared to Euro 5, and one of the ways to do this is the use of AdBlue.

How do you know if the car is equipped with AdBlue?

Perhaps it will be one of the criteria that will decide whether to buy the model you are interested in or give it up. And what if you are already a happy owner of a modern diesel car? You can easily check whether additional AdBlue maintenance duties await you.

First, read the car's owner's manual, if you have access to it. There should also be information about this system. If the car was produced after 2015, the SCR system is a given.

AdBlue in practice - what does refueling look like?

Fortunately, refueling with AdBlue does not require specialist knowledge or skills from the driver. The procedure is almost no different from the standard refueling at a petrol station.

adblue top up

How do you know when AdBlue is running out?

When the fluid level drops to an extremely low level, the car's on-board computer usually alerts you to add AdBlue. This, of course, is not a reason to panic - such a signal works on the principle of a reserve fuel lamp. Often, after the first signal from the computer, you can still drive up to several thousand kilometers. However, the moment of refilling should not be prolonged indefinitely - with a complete lack of liquid, you may encounter embarrassing situations and additional costs.

Where is the inlet to the AdBlue tank in the car?

When it comes to the fuel filler in passenger cars, the only dilemma comes down to the question: from the driver's or passenger's side. AdBlue, however, does not mix with the fuel at any time, so the location of the tank with this liquid is completely dependent on the manufacturer of the given brand. Look for the blue cap to find the sprue. It is usually located next to the fuel filler, but it can also be located in the trunk or even under the hood.

AdBlue tanks installed in passenger cars can usually hold from 5 to 22 liters of fluid.

How to top up the AdBlue level?

The AdBlue tank can be refilled directly from a special dispenser at the filling station, but not every tank is available. If you're lucky, you'll save quite a bit, because the price of AdBlue per liter is then much better than from a canister. However, this solution is still a rarity and drivers buy the necessary solution in special containers available, for example, in automotive shops or stations. 

AdBlue fluid is produced by different companies, but it does not matter much for its quality. When buying, however, pay attention to whether the product has been marked with the appropriate certificate of compliance with the ISO 22241-1 standard.

Some canisters have special dispensers to prevent accidental spillage on other parts of the vehicle. This is important because AdBlue is highly corrosive and also does not smell very pleasant.

Where to buy and how much does AdBlue cost?

AdBlue is generally available - you can buy it, e.g. In:

  • online stores,
  • official car dealers
  • automotive wholesalers,
  • at gas stations,
  • some supermarkets.

Unfortunately, liquid prices have increased significantly in recent months. Where does this tendency come from? The increase in AdBlue prices is the result of a sharp increase in gas prices - it is one of the most important raw materials used by chemical plants producing diesel fluid.

What to do when AdBlue runs out?

However, it may turn out that we forget about AdBlue, and then there will be little liquid left in the tank. However, we do not have to worry too much about this, because the car will send us a signal (sound or visual) that AdBlue is running out.

When the car sends a signal that the Adblue level should be refilled, do not panic. Usually you can still drive a few hundred kilometers by car. However, if we overdo it with the so-called AdBlue fumes, then we have to take into account that the car will automatically immobilize and start working only after adding this fluid.

However, it is better not to lead to such a situation, because some vehicles can only be restarted at an Authorized Service Station.

What are the advantages of using AdBlue?

The main advantages of using AdBlue are:

  • environmental protection,
  • reduction of diesel fuel consumption  (specific values ​​depend on the type of engine, but thanks to AdBlue, the vehicle can burn up to 5% less fuel, which means that AdBlue can not only earn money, but also generate savings),
  • discounts -in some European cities, AdBlue users pay less for entering selected zones.

Exhaust reduction systems with AdBlue allow you to adapt to the established emission standards. This has a positive effect on environmental protection and reduces the negative effects of the presence of nitrogen oxides in the air. This is important for both human and animal health. 

Even if the costs of AdBlue may cause negative feelings, compared to the benefits of its use for the environment, their importance is diminishing.

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