Diesel and AdBlue

Many new diesel engines use a fluid called AdBlue (Diesel Exhaust Fluid or DEF) to help reduce harmful exhaust emissions. This is an exhaustive additive. Now used in cars, vans and heavier vehicles, it is kept in its own special tank and is injected automatically in small quantities into the flow of the exhaust gases.

This colourless solution made from pure urea is injected into exhaust system, which helps remove the polluting nitrogen oxides. When AdBlue is injected into the stream of hot exhaust gases in the SCR system (Selective Catalytic Reduction), the harmful gases are broken down into pure nitrogen and water vapour. These clean gases are then expelled through the exhaust pipe.

Most diesel car and van drivers will need to top up the AdBlue between services, so it is important to keep an eye on dashboard warnings, particularly if you’re a high mileage motorist. Without AdBlue cars and vans will not run at all.

It is essential that AdBlue is regularly checked and the tank is not allowed to run dry.

In Euro5 and Euro6 vehicles lack of AdBlue puts the vehicle into Auto Limp Mode resulting in a dealer works visit to reset the computer and bleed the system. This information will stay on the system for 300 days and will register that the vehicle has been run without AdBlue. It can result in costs of £2,000 to clean the system.

• Follow any instructions given in your handbook or on the pack.
• Your handbook will tell you how much AdBlue the tank holds.
• You may need a funnel depending on where the AdBlue filler cap is located – next to the fuel filler, in
the boot, or under the bonnet – and the size/design of the AdBlue pack you’ve got.
• Wash your hands and rinse any spills from the bodywork – AdBlue’s non-toxic but can cause
irritation to your skin and eyes and will damage the paintwork.
• Do not pour AdBlue in the fuel tank or any other fluid instead of AdBlue in the dedicated tank for the
substance; it will severely damage your vehicle.

The more economically a vehicle is driven, the less AdBlue will be used. Vehicles using AdBlue are
equipped with special dashboard warning lights, but again the message displayed varies across
manufacturers. If the AdBlue tank is allowed to run dry, the vehicle is unlikely to start and large
service/maintenance costs will be incurred.

Keep your AdBlue topped up
Save unnecessary maintenance costs and drive safely