Diesel Engines, AdBlue and You

An overview of how AdBlue works in modern diesel engines, why it matters for Euro 6 emissions standards, and key tips for handling and topping up safely.

AdBlue filler point on a modern diesel vehicle.

Modern diesel engines fitted to vans, trucks and cars now feature Selective Catalytic Reduction (SCR) technology to reduce harmful exhaust emissions and meet today’s stringent Euro 6 emission standards.

As part of this process, AdBlue (a diesel exhaust fluid) is injected into the catalyst of the SCR system, where it reacts with exhaust gases to convert harmful nitrogen oxides (NOx) into harmless nitrogen and steam. In Euro 6 vehicles, AdBlue works alongside the Diesel Particulate Filter (DPF) to reduce overall emissions.

What is AdBlue?

AdBlue—also known internationally as DEF, ARLA 32 or AUS 32—is a colourless liquid made of 32.5% urea and demineralised water. It is non-toxic, odourless and non-flammable.

All major manufacturers—including Renault, Peugeot, Citroën, Volkswagen, Mercedes-Benz, Ford and Toyota—now produce vehicles equipped with SCR systems that require AdBlue.

AdBlue is stored in a separate tank and injected into the exhaust gases. It is not a fuel or fuel additive. Tank size and consumption vary depending on the vehicle, mileage, driving style and conditions.

A standard bottle of AdBlue diesel exhaust fluid.

Important Information

• AdBlue must only go in the dedicated AdBlue tank, never the fuel tank.
• If AdBlue is mistakenly added to the fuel tank, do not start the engine—seek dealer assistance immediately.
• Prevent contamination: keep AdBlue pure.
• If AdBlue spills onto paintwork, wipe off and rinse with water.

Dashboard warning light for AdBlue level/attention.

More details can be found on the TotalEnergies website.

Information courtesy of Maun Motors