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What is a diesel particulate filter?

A diesel particulate filter (DPF) is a device used in diesel engines to remove soot and other particulate matter from the exhaust gas.  DPFs are an important technology designed to reduce emissions and improve air quality. By trapping particulate matter, DPFs can help reduce health risks associated with diesel exhaust exposure and improve the longevity of diesel engines.

How does a DPF work?

DPFs work by trapping soot on the filter, allowing the exhaust gas to pass through. The trapped soot is then burned off during a process called regeneration.

How to regenerate a DPF?

Regeneration can occur passively (automatically) or actively, depending on the type of DPF.

Passive (or automatic) DPF regeneration occurs when the exhaust gas temperature is high enough to burn off the trapped soot. This can happen naturally when the vehicle is driven at highway speeds for an extended period of time. To automatically regenerate the filter, you must drive a vehicle at 50mph or above for at least 20 minutes. However, this may vary from manufacturer to manufacturer.

If the vehicle is primarily driven in stop-and-go traffic or for short distances, the exhaust gas temperature may not get hot enough for passive regeneration to occur. In these cases, active regeneration may be necessary. Active DPF regeneration involves adding extra fuel to the engine to raise the exhaust gas temperature and facilitate the burning off of the soot.

What happens if diesel particulate filter doesn't get regenerated?

Diesel particulate filters (DPFs) must regenerate in order to burn off the soot that has been trapped on the filter. If the trapped soot is not burned off, it will accumulate on the filter, reducing its effectiveness and increasing backpressure. This can lead to decreased engine performance and increased emissions.


To maintain Diesel Particulate Filter, it is important to follow the manufacturer's recommended maintenance schedule to ensure that it is regenerated properly and functions effectively. This may include cleaning the filter, replacing the filter, or performing a regeneration process.

Types of diesel particulate filters

There are two main types of DPFs: passive and active.

Passive DPF

Passive DPFs use a ceramic filter that is coated with a catalyst material. The filter traps particulate matter as the exhaust gas passes through it. When the filter becomes clogged, the engine's exhaust gases increase pressure, which triggers a regeneration process. During this process, the trapped soot is burned off, which regenerates the filter. Passive DPFs are generally less expensive and require less maintenance than active DPFs.

Active DPFs

Active DPFs use a catalyst to reduce the temperature at which the soot burns off. They also use a fuel injector to add extra fuel to the engine, which raises the temperature of the exhaust gases, making it easier to burn off the soot. Active DPFs are more expensive than passive DPFs but are more effective at reducing emissions.

Benefits of diesel particulate filters

DPFs can have several benefits, including:

- Reducing emissions of particulate matter
- Improving air quality
- Reducing health risks associated with diesel exhaust exposure
- Reducing engine wear and tear

Challenges with diesel particulate filters

Despite their benefits, DPFs can pose some challenges. These include:

- Cost: DPFs can be expensive to install and maintain.
- Maintenance: DPFs require regular maintenance to function properly.
- Regeneration: Regeneration can be a complex process, and failure to perform it correctly can damage the engine.
- Cold weather: DPFs are less effective in cold weather, which can lead to increased emissions.

Who should and who shouldn't opt for a diesel vehicle?

Diesel engines are generally not suitable for individuals or businesses that drive short distances or that primarily drive in highly congested urban areas. This is because diesel engines are most efficient at highway speeds and require a certain amount of time to warm up and reach peak efficiency. Additionally, diesel engines can produce higher levels of particulate matter and nitrogen oxides, which can contribute to air pollution and health risks in densely populated areas.

However, for those that frequently drive long distances or primarily operate in rural areas, diesel engines can offer improved fuel efficiency and reduced operating costs compared to petrol engines.

Alternative vehicles

For individuals or businesses that primarily operate in urban areas with high traffic congestion, diesel engines may not be the most suitable choice. Alternative vehicles such as hybrid or electric vehicles may be a better option, as they produce fewer emissions and are more efficient in stop-and-go traffic.

We are here to help

Our team is happy to answer any questions you have and help you determine whether a diesel engine or alternative vehicle is the best choice for your needs. Additionally, the above guide provides comprehensive information on diesel particulate filters (DPFs), how they work, their benefits, and maintenance requirements.

If you have any further questions or concerns, feel free to reach out to us by calling us on 01424 863 456, or to send us a message.