What Is AdBlue? How AdBlue Works For Diesel Engines


You may have noticed a mysterious liquid called AdBlue on your trips to your petrol station. Unless you use it regularly, you may be asking yourself, ‘What is AdBlue?’ 

We’re going to explain exactly how AdBlue works and when you might need to buy some for your own vehicle. Keep reading for everything you need to know!

What Is AdBlue Fluid?


AdBlue is an exhaust fluid that reduces nitrous oxide emissions in diesel cars. It is not an additive to your fuel and is stored in a separate tank inside your car.

The fluid is sprayed into the exhaust system of diesel vehicles and it neutralises some of the harsh chemicals coming from the pipe.

AdBlue is the most recognised form of the generic term Diesel Exhaust Fluid.

Originally, AdBlue was stored in a sealed tank and drivers didn’t have to worry about it. That was when vehicle services were every 10,000 miles. However, service intervals have risen, which means drivers now refill AdBlue themselves.

You may have noticed it for sale at petrol stations, car garages, or even your supermarket. It’s only for diesel vehicles though. So, anyone who has a petrol or electric car needn’t worry about how to use it. 

What Does AdBlue Actually Do?


Tiny droplets of AdBlue are injected into your exhaust flow which creates a chemical reaction with the fumes. 

At the high temperatures your vehicle runs at, AdBlue turns to ammonia and carbon dioxide. This converts harmful chemicals like nitrogen oxide (NOx) into harmless water and nitrogen.

NOx gases contribute to acid rain, smog, and ozone troubles while also causing breathing complications for people.

It has been used in heavy-duty vehicles like lorries and buses for decades, and AdBlue for cars is now essential. In fact, since 2015, AdBlue in diesel engines has been compulsory to comply with Euro 6 emissions laws.

Many diesel cars since 2006 from France and Germany have included AdBlue conversion. But now the rest of the automotive world has caught up. 

Today, vehicles have to adhere to strict rules about emissions and the technology known as Selective Catalytic Reduction (SCR) helps AdBlue do its job.

What Is AdBlue Made Of?


AdBlue isn’t actually blue at all. In fact, it is completely colourless. 

It is made using a combination of deionized water and urea. That’s right, urea, which can be found in urine. 

The urea is not sourced from actual urine, however. It’s actually a man-made version that is non-toxic.

It needs to be sterile, and using waste from humans or animals simply wouldn’t be clean enough.

Both the water and urea need to be clean and pure to ensure the chemical reactions occur successfully in the exhaust system.

When To Use AdBlue


Keeping your diesel vehicle topped up with AdBlue is quite important because it can affect the engine performance. This is because your car will stop working at such a high level to ensure it complies with emissions regulations.

We recommend making plans to top it up whenever the AdBlue warning light can be seen on your dashboard. Thankfully, when the light does go on, you do have around 1,500 miles to go before it runs out.

If you let your AdBlue tank run completely empty, the engine won’t start the next time you try to turn it over. People who don’t drive too often may never have to top up their AdBlue because it is done at every service.

Tank sizes do vary though, and they can run empty from as little as 3,000 miles up to around 12,000. Your driving style and engine size will also impact how fast your AdBlue runs out.

Where Is The AdBlue Tank?


Many drivers will have to top up their AdBlue themselves. But often, people don’t know where to refill it from.

Typically, the AdBlue filler can be found in one of three places:

  • Beside your fuel filler
  • In the boot
  • Under the bonnet

Some people may know where it is already because a lot of the time it is directly beside your fuel filler.  Other AdBlue filling locations may be in the boot of your car or under the bonnet.

Once you have found the filler it’s time to top up the tank. Be careful not to spill any liquid onto your car. 

While it is non-toxic for humans, it can strip the paint from your car or damage any hidden wires.

When you buy a new car which is diesel, you can ask the salesman where the AdBlue filler is.  Although this information will also be available in your driver’s manual.

You may even find an AdBlue pump at a filling station, as many truck and bus drivers have been using it for years. 

Originally, AdBlue pumps at filling stations were only found on major routes. But they are more readily available as more and more vehicles use it.

Thanks to AdBlue, diesel cars produce much less harmful fumes than without it. 

Hopefully, we have answered the question, What is AdBlue?’ and you no longer have to wonder what AdBlue is and how it works. We hope that you found this article helpful! 

For more advice on car maintenance, check out our blog.

Other items you might consider keeping in your boot are car battery chargers and jump leads. Check out our Emergency Car Kit Checklist to find out more.

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