Diesel Vehicle Fact Sheet

AdBlue® and Diesel Particulate Filter (DPF)

As part of the drive to reduce harmful emissions associated with diesel vehicles, technologies such as Selective Catalytic Reduction (SCR) and Diesel Particulate Filters (DPF) have become commonplace. So to ensure you have all the information needed to make informed decisions, and keep your vehicle running smoothly, here is a summary of the key facts.

Selective Catalytic Reduction (SCR).

Used correctly, SCR is reported to help reduce the level of Nitrogen Oxide (NOx) emissions by up to 90% and could potentially reduce the amount of fuel used by between 3% and 5%.

Vehicles with SCR are fitted with an additional tank, specifically designed to store a liquid reductant agent known as AdBlue®, which you can buy from selected vehicle dealers and fuel stations. Your vehicle manual will tell you which warning lights and sounds indicate that it is time to refill the tank and how to go about it. It is important to pay swift attention to these warning signs, as ignoring them could see your vehicle go into “limp home” mode (run on reduced power) or it may simply not re-start once the ignition has been switched off.

Just like fuel, the cost of refilling the tank with AdBlue® is the responsibility of the individual vehicle driver or their employer. However, where the service schedule states that the fluid should be changed (rather than topped up), and you have a maintenance contract as part of your agreement, the cost will be covered.

Diesel Particulate Filter (DPF)

Almost all diesel vehicles are now fitted with a DPF designed to catch soot in the exhaust and prevent it from entering the environment.

To keep everything running smoothly, the filter needs to be regularly emptied using a process known as regeneration. This is when the soot is burnt off at a high temperature, leaving just a small residue of ash. It’s a process that takes place automatically when driving at motorway speeds because the exhaust reaches a high enough temperature for the regeneration process to occur.

On the other hand, if a vehicle is mainly driven for shorter distances, at slower speeds, the cleaning process will not take place frequently enough to keep the filter clean. In these circumstances, most vehicles will initiate a forced regeneration by boosting the exhaust temperature to a point where regeneration will occur. However, this can mean that you need to keep driving for 10 minutes or so at speeds greater than 40mph until the process is complete and the warning light clears.

If the warning light is ignored, soot levels will continue to rise and the vehicle may enter a ‘restricted performance mode’ to limit any further damage. At this point, the vehicle will need professional attention to clean or even replace the DPF. This can easily cost upwards of £1,000 and is not covered by either your warranty or any maintenance agreement you may have with us.


To protect your DPF and keep it running smoothly, it is important to follow the guidance found in your vehicle handbook and, if any warning lights come on, take the recommended action immediately.