DPF Cleaning, Regeneration & Replacement

DPF is an abbreviation used to refer to the diesel particulate filter – a relatively recent addition to the exhaust system of diesel cars designed to filter out by-products of incomplete fuel combustion.

Diesel engines produce large amounts of particulate matter, or soot when they burn fuel as part of the combustion process. This soot is known to cause a number of serious health issues, namely breathing problems. Legislation making the inclusion of DPFs mandatory on all new diesel vehicles was introduced in 2009 with the intent of managing issues related to the excessive production of particulates.

The DPF catches particulates using a filter, which becomes clogged over time. The material trapped within the filter is heated by the exhaust, turning to ash when temperature requirements are reached. This occurs when the car is travelling above 40mph, or automatically every 300 miles. This ash is then expelled. This process is generally known as regeneration.

The two primary issues DPFs tend to experience are clogging, and failure. If your vehicle’s DPF light is illuminated, contact Bosch Auto Serice for expert advice, or to book in for an inspection with one of our experienced technicians.

All diesel vehicles built after September 2009 and sold in the UK are legally required to be fitted with a DPF under the Euro 5 standard for diesel cars. If your car was manufactured around or after this date, it is highly likely that a DPF will be fitted to its exhaust system. It is also important to note that many cars built prior to this date also have DPFs fitted.

An easy way to confirm whether or not your vehicle has a DPF is to check the manual, where all relevant information regarding the DPF and exhaust system will be stored.

Most vehicles fitted with a DPF are equipped with sensors set to monitor the levels of soot present inside the filter, helping the engine determine when regeneration is necessary. Upon reaching a threshold determined by the manufacturer (typically around 45%), the engine will activate the regeneration process wherever possible. However, if this process is unable to take place due to, for example, low speeds, or short driving times, the DPF warning light will illuminate in order to alert the driver of increasing soot levels.

This can usually be rectified by driving for around 10 minutes at speeds over 40mph, allowing for the regeneration process to take place, and the soot levels to fall.

If the light is ignored and soot levels continue to increase, the vehicle may resort to imposing a reduced top speed limit, in order to prevent further soot build-up. At this point, a visit to a technician is often necessary to induce forced regeneration, or, in extreme cases, replace the DPF.

DPF filters, like most car parts, have a limited lifespan, influenced by factors such as conditions, maintenance frequency, and driving style. A DPF should typically last for more than 70,000 miles, however, filters lasting for significantly longer, or shorter periods than this is possible.

Maintenance is an important factor in extending the lifespan of any car part. The most effective form of DPF maintenance is allowing for frequent regeneration, in order to keep the filter clear from blockage. This can be done by ensuring the vehicle is regularly driven at speeds of over 40mph for periods of 10 minutes or more.

If your DPF warning light is illuminated, it is likely that a blockage is present, meaning forced regeneration, or part replacement is necessary.

Common causes of DPF blockages include;

Frequent short, low-speed journeys, or excessive idling – travelling for a short amount of time at a low speed does not allow the exhaust system to reach the minimum temperature required for regeneration, leading to soot build-up within the filter, and eventual blockages

Faulty fuel injectors – faults with a vehicle’s fuel injectors can lead to imbalances in the fuel to air ratio, causing the engine to produce higher quantities of particulates

Incorrect engine oil – most manufacturers specify low SAPs engine oil for use in diesel cars. This oil reduces the production of sulphated ash, one of the main particulates caught in DPF filters

Faulty turbocharger – faults with the turbocharger can cause imbalances in fuel to air ratio, or even flood the DPF with oil, both of which can lead to the excessive production of soot and blockages

A DPF blockage will most commonly be indicated by the illumination of the DPF warning light. The most effective way to clear this blockage is to ‘clean’ the DPF through the process of regeneration.

The cleaning process typically involves driving for around 10 minutes at speeds over 40mph, allowing for the regeneration process to take place, and the soot levels to fall.

If the light is ignored and soot levels continue to increase, the vehicle may resort to imposing a reduced top speed limit, in order to prevent further soot build-up. At this point, a visit to a technician is often necessary to induce forced regeneration, or, in extreme cases, replace the DPF.

If your vehicle’s DPF light is illuminated or you believe your DPF is in need of a check-up, contact Auto Service & Tuning Centre for expert advice, or to book in for an inspection with one of our experienced technicians.

Checks for the presence of a DPF in diesel cars were introduced as part of the MOT in 2014. If the DPF is not present or has been removed, the vehicle will automatically fail its MOT, as DPFs are a legally required part on all diesel vehicles produced after September 2009.

The illumination of the DPF warning light or any warning light on the dashboard will also result in an automatic MOT failure.