Diesel exhaust fluidBelgium
Learn traffic rules with clear explanations and visual examples in our illustrated book, designed to make studying simple and engaging.
148. Diesel exhaust fluid
Diesel exhaust fluid (DEF) is a liquid used by many modern diesel vehicles with selective catalytic reduction (SCR) systems to reduce harmful nitrogen oxide (NOx) emissions. In Europe it is commonly known by the trade name AdBlue.
DEF is not diesel fuel and is stored in a separate tank. It is a solution containing high-purity urea and water that is injected into the exhaust system, where it helps convert nitrogen oxides into less harmful substances.
Wikimedia.org • Lenborje • CC BY-SA
What is diesel exhaust fluid called in Belgium?
Diesel exhaust fluid is commonly known as AdBlue in Belgium. It is used by diesel vehicles equipped with selective catalytic reduction systems to reduce nitrogen oxide emissions.
Can AdBlue be added to the diesel tank?
No. AdBlue and diesel must be kept completely separate. AdBlue has its own tank and filler opening, and putting either liquid into the wrong tank can cause serious vehicle problems.
Should you refill AdBlue when the dashboard warning appears?
Yes. The warning indicates that the AdBlue level is becoming low. Drivers should refill it with a suitable product according to the vehicle manufacturer's instructions rather than waiting until the tank is empty.

Traffic rules
Belgium