What is a DPF?
A DPF is a Diesel Particulate Filter (also known as FAP on some French vehicles).
It is a device fitted to the exhaust system of modern diesel vehicles to reduce emissions and meet European emission standards.
How Does a DPF Work?
Particulate filters work by trapping Soot (particulate matter) from the exhaust gases of a diesel engine, whilst still allowing gases to flow through the system.
As with any type of filter, DPFs require regular cleaning to function properly. DPFs are automatically cleaned during regular car operation through a process known as Regeneration.
What is Regeneration?
DPF Regeneration happens when the car exhaust reaches a suitably high temperature. The soot is then converted to gas with the assistance of a catalyst in the system.
For regeneration to take place the vehicle must be driven regularly at around 2500RPM or more for at least 30mins, once a month.
Regeneration still leaves behind an ash residue within the filter as the process isn't always 100% effective. It's also common for cars to be only used for short local journeys, leading to soot build-up over the life of the vehicle.
What Problems Can a DPF Encounter?
If regeneration cycles don't complete fully, due to the age of a car or lack of long journeys, the resulting sooty deposits can affect performance and fuel economy. Left unattended, they will result in a blocked DPF, which can ultimately cause expensive damage to other engine components.
A blocked DPF is also potentially dangerous as it can cause overheating in the exhaust system and increase fire risk. To prevent damage, newer vehicles will automatically go into “Limp Home” safety mode when an issue is detected.
What cars feature a Diesel Particulate Filter?
Since 2009, diesel engines in the UK must have a DPF fitted. Cars older than this may still have one installed, but we can let you know if you are unsure.