Emission control with AdBlue®1

AdBlue is an additive used in the SCR2 system to reduce emissions of noxious substances from a diesel engine.

In the SCR system, the AdBlue and the nitrous oxide exhaust gas substance are converted to nitrogen and water vapour, which significantly reduces the emissions of harmful nitrous oxides.


AdBlue is a colourless fluid that consists of 32.5% urea3 in deionised water and is produced in accordance with the ISO 22241 standard. It is specially developed for SCR cleaning technology for diesel engines.

AdBlue has its own tank in the car and is topped up via a separate filler pipe behind the fuel filler flap. Consumption depends on driving style, outside temperature and the operating temperature of the system.

Conditions for driving with AdBlue

There must always be AdBlue of the correct quality in the tank before the car can be started. The SCR system is very sensitive to contaminants.

The emission control system continuously monitors the tank level, quality and dosage of AdBlue. If something is wrong, a message is shown in the driver display.


AdBlue is required for the function of the SCR system and legal emissions compliance. It is illegal to modify or manipulate the AdBlue supply system in any way so that no AdBlue reagent is consumed when it is required for legal exhaust emissions compliance. Any such tampering may be a criminal offence which may lead to legal prosecution actions.

It is not permitted to operate the car with an empty AdBlue tank, since it will no longer be compliant with the legal requirements for exhaust emissions. Therefore, the car is equipped with a warning system to inform when AdBlue refilling is required. When the fill level in the AdBlue tank is getting low, warnings are displayed to inform that AdBlue refilling is needed.

  1. 1 Registered trademark that belongs to Ver-band der Automobilindustrie e.V. (VDA)
  2. 2 Selective Catalytic Reduction
  3. 3 CO(NH₂)₂