Add blue is the miss spelling of the brand name AdBlue.

Selective Catalytic Reduction (SCR) is a technique used to clean up diesel emissions. Exhaust gases can be treated with AdBlue to remove harmful pollutants, including nitrogen oxides (NOx), of which nitrogen dioxide (NO2) is the most harmful.

AdBlue is a colourless liquid made up of high purity urea and deionised water, and vehicles with SCR technology will have a separate tank filled with it.

Unlike diesel or petrol it is not injected into the engine,instead it is released into part of the vehicle’s exhaust. When heated in the exhaust, it decomposes into ammonia and CO₂. The NOx from the engine exhaust reacts inside the catalyst with the ammonia and the harmful NOx molecules in the exhaust are converted to harmless nitrogen. In fact, AdBlue® can reduce your NOx emissions by up to 90%!

AdBlue is a registered trademark owned by the German Association of the Automobile Industry (VDA), which ensures standards are maintained.

No data has suggested that AdBlue has any adverse effects on fuel consumption.

Don’t start the engine; you will risk writing off the engine and fuel system. Call a breakdown company or misfuelling service provider and get the fuel tank emptied and flushed out.

Don’t start the engine; call your breakdown service provider to get the tank drained. If you start the engine, you could damage the SCR (Selective Catalytic Reduction) and AdBlue injection systems and they may then have to be replaced.

The Warning Light is there to tell you that you are running low on AdBlue. The vehicles information display screen will flash up warnings, the same as if your fuel was low. Failing to act on these warnings will result in the vehicle refusing to start until the AdBlue tank is filled.

The amount of AdBlue used depends on the type of driving being done and the number of miles covered.

The engine wouldn’t cut out the same as it would if you ran out of fuel, however the AdBlue is integral to diesel vehicles. This means your vehicle treats it like fuel and won’t run properly without it.

If you ignore the warning light and the AdBlue runs out the vehicle’s performance will be adversely affected (the vehicle does this to prevent any potential damage to the system occurring). Once you turn the engine off it will not restart if the AdBlue has run out.

Most vehicles will display a warning light on the dashboard when the AdBlue is running low.

The majority of AdBlue tank filler spouts are located adjacent to the diesel spout. In most cases they will have a blue cap to help distinguish them. The vehicles handbook should tell you its location.

Any spillages of AdBlue should be washed away with water.