Frequently Asked Questions

A diesel particulate filter (DPF) is a filter that is designed to collect the soot thats created when diesel is burned, preventing harmful particles from being pumped out into the atmosphere.

Diesel particulates are from the incomplete combustion of diesel fuel, which produces soot particles. Soot and other particles from diesel engines worsen the particulate matter pollution in the air and are harmful to health.

Although particulate filters are very effective in dramatically reducing the amount of particulates emitted from diesel vehicles, most filters need to burn the trapped particulates off fairly regularly, known as regeneration.

A DPF can hold a certain amount of soot, but not a huge quantity, so it needs to regularly go through a process of regeneration in order to clear out the soot and allow the vehicle to operate correctly. Regeneration occurs when the filter reaches a sufficiently high temperature, allowing the soot to be converted to a much smaller amount of ash.

To allow the DPF to automatically regenerate, the engine should be used regularly at a sufficient speed, to ensure a high enough temperature of the exhaust gas is reached. Although it may vary from manufacturer to manufacturer, typically a vehicle must be driven at 50mph or above for at least 20 minutes in order to automatically regenerate the filter. During the regeneration phase, high temperatures in the filter may cause a slight smell, especially during the first regeneration.

Stop/start short journeys at low speeds are the main cause of blocked diesel particulate filters. If a car spends most of its time being driven around town on short start-stop journeys, the exhaust doesn’t get up to temperature so the soot doesn’t get burnt off and the DPF does not ‘regenerate’ on its own.

Other most common reasons for DPF failures include a clogged EGR Valve causing excess soot, faulty fuel injectors sending too much fuel to the air/fuel mixture, wrong type of engine oil, high mileage car will find regeneration harder, low fuel level – generally less than a quarter of a tank – will prevent regeneration taking place.

DPFs are designed to last in excess of 100,000 miles but if the drivers fail to operate the vehicle correctly, it will fail a lot earlier.

If your warning light continues to stay on, turns red, or additional DPF lights come on, do not leave it too long before getting it checked by a specialist.

More damage can be caused this way and what could be an inexpensive fix can become something much more expensive.

Some garages can clean blocked DPFs, in a process called forced regeneration but this is found to be a temporary fix and just masks the problem for a period of 2-4 weeks and the same issue will occur again. Failure to correctly fix the issue that is the cause of most diesel particulate filter issues: they become blocked more and more which increases exhaust emissions, stifles engine performance and sometimes even puts the car into a restricted ‘limp-home mode’. On some models the engine may not restart after a number of miles, constantly driving with a blocked DPF can cause further damage to components causing real problems

When you see a flashing DPF warning light, you may consider removing it to solving the problem. This is not a great move for the planet and is, as mentioned, illegal in some places. Moreover, as of recently, cars that have had their DPFs removed will fail their MOT. It can be done, and you will find companies offering this service online, but it is just not worth it. It can even invalidate your motor insurance.

Diesel particulate filters are very expensive. A new one from a car manufacturer can cost £1,000 and £3,500, plus any diagnostic or labour charges, There are now other suppliers of diesel particulate filters that charge less, but be careful as they must still have the correct Type Approval or they may not work correctly and end up costing you more in repairs leaving you again with high repair bills.

It is natural that your DPF will become clogged, especially if you do not make frequent long-distance journeys. However, there are ways of helping your DPF stay clean. You need to make sure you use the right type of oil. Choose oil which is low SAPS. The fewer number of sulphate ash particles the less chance of your DPF clogging up. The second way to keep your DPF clean is to get a professional DPF cleaning company to take a look at your DPF at regular intervals.

If you suspect your DPF s clogged or you have seen your DPF warning light, then you need to act.

With our state-of-the-art equipment, we offer roadside DPF cleaning to get you on your way again, fast. Whether it be a van, a car or a lorry, our specialist equipment is capable of identifying your DPF’s performance and bringing its levels of soot and matter back down to an immaculate clean. We can even provide you with the before and after results to show you our work that has saved you money in the long term.