Increasingly strict emissions standards have forced manufacturers to look for ways to keep their cars on the road. In the case of the more powerful diesels, the trick for passing the European tests is called AdBlue.

1. What is AdBlue?

Without going into excessive technical detail, we can sum it up by saying that AdBlue is the trade name of an aqueous urea solution at a concentration of approximately 32.5%.

Yes, just as you are thinking: urea is a chemical compound present in urine and, although it is not toxic, it is corrosive. This means it can be handled, but taking care that it does not touch the bodywork; for this same reason it is advisable to clean the area around the filler after topping it up.

2. What is AdBlue used for?

AdBlue is an additive used in some cases to help diesel engines meet the strict European Euro 6 emissions standard.

The Euro 6 standard came into force on 1 November 2015 with the aim of making all new vehicles sold on European soil reduce their emissions of pollutants and particulate matter — in other words, making them cleaner.

 

Compared with Euro 5, the new European anti-pollution standard reduces nitrogen oxide emissions from diesel engines — the most harmful to people’s health — from 180 mg/km to 80 mg/km, while particulate matter keeps the same limit. For petrol engines, meanwhile, the limit of 60 mg/km of NOx does not change, nor does the particulate limit, set at 5 mg/km.

To comply with the legislation, manufacturers have improved exhaust gas treatment systems, using a NOx catalytic converter in lighter models and a catalyst with urea injection, also known as AdBlue, in heavier ones.

3. How does AdBlue work?

Diesel engines produce less CO2 and fewer pollutants, but they emit far more NOx and benzopyrenes than petrol engines.

Benzopyrenes are found in the ash produced by diesel combustion. They are particles that adhere to the tissues of the respiratory system, hence their danger. To reduce their impact, cars are required to have a particulate filter: a screen fitted in the exhaust pipe that traps the particles and prevents them from leaving the engine system.

Nitrogen oxide (NOx) is highly polluting and harmful to health; that is why diesel vehicles are so frowned upon in cities.

Since it cannot be removed physically, a chemical reaction is needed to turn it into harmless particles. In diesel engines this reaction is achieved with a catalyst — the place where the process takes place — and a chemical compound, AdBlue, which reacts with the NOx and converts it into harmless gases, specifically nitrogen and water vapour.

4. How much does it cost to refill AdBlue?

For each 20-litre container of AdBlue you will pay around 40 euros. At first it may seem expensive, but bearing in mind that this amount will last you up to 20,000 km, it really isn’t.

Although each manufacturer does it their own way, a warning light usually comes on when there are about 2,000 km of range left with the additive. This is important to keep in mind because if you run out of AdBlue in the middle of a journey the car will keep running without any problem, but once you stop it, it will not let you start again until you have topped it up and the electronic unit has been reset.

5. How is AdBlue topped up?

Technically, to fill the AdBlue tank you simply open the cap of the urea tank and fill it.

The problem if you want to do it yourself is that, in order to drive again without any issues, the electronic counter needs to be reset, and for that you need a diagnostic machine.