What is Ad Blue

What is AdBlue or Ad Blue ?


Ad-blue was introduced because of the EU Euro 6 standards that demand a drop of 67% in NOx (nitrogen oxides) in diesel car emissions. So most car manufacturers looked for a way to adjust their diesel engines in such a way that it will meet these demands without losing performance.

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There are two ways of reducing NOx:

  • Exhaust gas recirculation
  • Selective catalytic reduction

Exhaust gas recirculation

It uses a recirculation system that uses intake air to replace some of the exhaust gases to reduce the NOx. If your car has a similar system, you do not need AdBlue.

Selective Catalytic reduction

This system uses a special a fluid called AdBlue, or AdBblue, to break NOx into other elements that are completely harmless.

Ad Blue is used only in diesel engines so, if you have a petrol engine in your car, you do not need Ad-blue. Ad-blue is a colorless liquid, non-toxic, made from urea and deionized water. Ad-blue has a separate tank in which it is stored.

How does it work?

When your engine is running, a tiny amount of AdBlue is injected into the exhaust gas. Here, it reacts with the NOx from the exhaust gases, turning NOx into Water and Nitrogen.  

Ad-Blue was introduced on Euro 6 engines, starting from September 2015. Thus, if your car was produced after September 2015 and uses a Euro 6 Diesel engine, then most likely your engine needs AdBlue.

How much do I need?

Well, this depends on the cylinder and power of your diesel engine. Usually, your engine will use 1 liter of Ad Blue for 20 liters of diesel, or approximately a 5% ratio.

This value is an estimation, and your car can use a bit more or a bit less. For example, Audi uses a 12-liter tank for Ad Blue in the A4 and based on their estimation, that 12-liter tank should be enough for 6000 miles.

Where is the tank and how to top up?

Well, this is a tricky question. Every manufacturer placed this Ad Blue Tank in a different zone. Some placed it near the fuel tank, others in the trunk while some of them, like Mercedes, placed it in the boot. Usually, you will find a clear label AdBlue on the Ad-Blue filler cap.
Your car owner’s handbook should pinpoint the exact location of the Ad-Blue tank.  

One thing you should keep in mind when adding Ad Blue to your car is that AdBlue is highly corrosive, especially to aluminum and other materials. Because of this you should use special materials and make sure you don’t spill it on your trunk’s carper, on your car’s paint and so on.   

What happens if the car runs out

Since a full tank of ad blue can last up to 10000 miles, running out of AdBlue is a bit unlikely. But, before running out your car will display a warning when the tank is almost empty. This warning, which will appear as a warning/light on your dashboard, indicates that you have around 3 liters of Adblue left, which are enough for 1200 miles, or so.

Don’t ignore this warning because if you do, when the ad blue tank will be over your engine’s performance will be greatly reduced. More importantly, if you stop the engine, it won’t start again if the ad blue tank is empty. Only in 2017, there were more than 20.000 reports of AdBlue breakdowns.

Where to buy

You can buy Adblue from almost every auto part store and gas station, or online. Most gas/petrol stations even have Adblue pumps as well. If you want to buy ad blue in containers, expect to pay around 2 Euro/liter.

Keep in mind to buy Adblue only from recognized petrol stations or good merchants. This way you won’t buy ad blue with lower urea concentration than standard.

AdBlue: Conclusions

Adblue is an SCR (Selective Catalytic Reduction) technology build with one idea in mind: to keep the diesel engines on the road for several decades, while keeping the emissions as low as possible. This way, we can keep producing diesel engines for the next 40 or 50 years, until we run out of oil.

If you like our website you can read more articles, like our Top Best Tires for SUV, All Season.

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