This site uses cookies to improve your experience of our site.
If you continue we will assume you are happy with our use of cookies. Find out more here Close

What is a Diesel Particulate Filter?

Most modern diesel vehicles are fitted with a Diesel Particulate Filter (DPF) which removes harmful soot from the exhaust gases before they enter the atmosphere.

Why have a DPF?

In order to meet strict European emissions legislation, DPF's are used to help reduce the amount of pollutants from diesel engine vehicles. Using advanced technologies, the DPF reduces exhaust smoke and black soot, significantly lowering emissions and protecting the environment.

How does the DPF work?

As well as converting harmful exhaust gases in the same way as a conventional catalytic converter, the DPF also 'traps' soot particles (par- ticulates) that are produced in the exhaust gas. The DPF continues to do this until a predetermined level is reached, at this point it will promptly clean itself by heating up and burning off the accumulated soot particles. This process is known as DPF Regeneration.

How will the DPF affect me?

In order to carry out the regeneration, the DPF needs to reach and maintain a higher exhaust temperature than normal. Under most conditions, your car can do this unaided. However, in some circumstances, it can't reach the required temperature (usually due to frequent short jour- neys or stop-start driving), in which case the driver is normally alerted by a warning light and/or a message appearing in the instrument panel, depending on the make and model of the vehicle.

What should I do if the warning light comes on?

Firstly, do not ignore it. If the light has come on, it does not necessarily mean there is a fault. It's simply telling you that the Diesel Particulate Filter on your car needs help in carrying out the DPF Regeneration. To do this, you need to drive in a particular way to increase the exhaust temperature - typically 10-15 minutes at a suitable road speed, whilst maintaining an engine speed of approximately 2,500rpm. (This may vary depending on make and model of vehicle). If you fail to address the issue, the DPF light stay on and additional lights or symbols may also come on as soot levels will continue to increase. Check your vehicle handbook for details.

You may also experience a reduction in power, followed by a complete DPF blockage and the need for a costly replacement filter.

What happens if two or more lights come on?

If more lights come on, the DPF Regeneration can usually only be carried out at an authorised repairer and should be done immediately. Apart from a reduction in engine power, the engine may fail to start if ignored.

Is there anything else I should know?

If the DPF needs replacing as a result of ignoring the warning lights or mes- sages, the cost of replacing the DPF may not be covered by the manufac- turer's warranty, if still in force.

Note, if your car is fitted with a DPF, you should not use 100% RME (rape- seed methyl ester) biodiesel as this can cause damage to the fuel system. Use forecourt BS EN 590 diesel only. 


01993 894981
Government concludes its inquiry into emissions tests

Vehicles tested by the UK government showed no evidence of car manufacturers apart from the VW Group - fitting devices to defeat the emissions test programme. read more

What is a Diesel Particulate Filter?

Passenger Car Diesel Particulate Filter read more

Lease or Buy a new car/van?

Key questions to ask yourself, to help you decide whether to lease or buy a new car/van read more

» Browse all articles