AdBlue is a diesel exhaust fluid used in vehicles with Selective Catalytic Reduction (SCR) technology to reduce harmful gases being released into the atmosphere. It is a clear mixture of demineralized water and pure urea (32.5%) . AdBlue is used in diesel cars built after September 2015 to decrease the amount of nitrogen oxides emitted from their exhausts. It is injected into the exhaust system of diesel vehicles to reduce nitrogen oxide (NOx) emissions. AdBlue helps to reduce pollution by breaking down the nitrogen oxides into nitrogen and water, which are harmless. AdBlue is essential for vehicles to comply with the emission standards set by the Euro 6 regulations.

AdBlue is used in vehicles with SCR technology, which have a separate tank filled with AdBlue. This is then injected into the exhaust pipe, in front of the SCR catalyst, downstream of the engine. Heated in the exhaust, it decomposes into ammonia and CO₂. When the NOx from the engine exhaust reacts inside the catalyst with the ammonia, the harmful NOx molecules in the exhaust are converted to harmless nitrogen and water, which are released from the tailpipe as steam.

If you own a diesel car built after September 2015, the chances are it’ll need AdBlue at some point. Modern diesel cars have a dashboard warning light to tell you if you’re running low, just like when you run out of washer fluid or run low on oil. You can buy AdBlue from major retailers such as Halfords. When driving a vehicle using AdBlue, you will get a message on the dashboard if the AdBlue needs to be topped up. You can do this yourself or have it done at your garage. It is important to follow up this message as soon as possible; a too low AdBlue level may prevent your vehicle from starting.