What is a DPF | Everything you need to know about

Turborevs features everything you need to know about a DPF.

A diesel particulate filter or a DPF is a standard device that is commonly found in diesel vehicles. These devices are highly delicate, and even the slightest maladjustments can result in hefty costs for your vehicle. Understanding what these devices do and how to maintain them is essential, especially if you own a diesel-powered heavy-vehicle.

To guide you on all the aspects of a diesel particulate filter, Turborevs has compiled an in-depth guide on everything you need to know about a DPF.

What is a Diesel Particulate Filter?

Diesel Particulate filters are essential devices.

Similar to a catalytic converter, a diesel particulate filter is a device that is meant to reduce emissions in diesel vehicles. The device has a simple functioning, as it captures and stores exhaust soot from the vehicle’s exhaust system. Without these filters, the soot would directly pollute the environment, increasing diesel emissions by several folds. 

Since the capacity within these filters is limited, the stored grit is constantly burnt off at regular intervals. As the process cleanly burns the remains off, the smoke emitted by diesel vehicles becomes slightly cleaner, deviating from the standard black smoke emitted by these vehicles. 

How Does a DPF Function?

DPFs have a relatively simple functioning, however, the process of burning off the grime can be slightly complicated. As the exhaust gasses pass through the diesel particulate filter, the soot released by the exhaust system starts getting trapped within the filter. The soot is a by-product of incomplete combustion within diesel engines, when the air fuel mixture fails to completely combust.

The grime collected within the filter has to be cleaned or burned off, since the filter can get clogged up. This is done through a process known as ‘regeneration’. As the temperature within the exhaust starts to soar, the soot starts to heat up, turning into ashes which are then easily expelled out. This process only takes place at speeds above 40 mph, or when the engine automatically raises the temperature after every 300 miles. 

How to Maintain a DPF?

DPFs need to be regularly maintained

Maintaining a diesel particulate filter is quite simple, as the only thing you need to ensure is whether the regeneration process is actively taking place or not. If the filter is unable to clear off the accumulated grime, it could be a sign of damage. There are two types of regeneration processes that can clear out the clogged-up soot. 

Passive Regeneration

Passive regeneration is an automatic process that allows the vehicle to naturally burn the accumulated soot within the filter. Since the engine can get quite hot, the heat is transferred through the exhaust system, heating up the excess soot to the point where it turns into ashes. As the soot is mostly carbon residue, it reacts with oxygen to form carbon dioxide, which easily passes through the exhaust system. 

Carbon dioxide is relatively less harmful for the environment, especially compared to the other emissions produced by vehicles. Therefore, the device makes diesel vehicle’s slightly less pollutive. However, since ash cannot pass through the filter, it has to be regularly cleaned out manually. 

Active Regeneration

Contrary to passive regeneration, active regeneration requires the engine to actively produce high levels of heat to burn down the soot. This happens when the engine is unable to naturally produce the heat required to burn the grime. This occurs when the vehicle is either not fast enough, or the engine is not bearing any extra load. 

Once the levels of grime in the filter reaches a certain point, the vehicle’s engine injects fuel into the exhaust stream, which oxidises to create more heat. The resulting heat is then used to burn down the soot into ash and carbon dioxide. 

Both types of regeneration take place automatically, without the driver taking part manually. However, in active regeneration, the driver is notified that the DPF is full, indicated by a dashboard lamp. 

In Case Regeneration Fails

In cases where the vehicle is unable to perform both active and passive regeneration, the vehicle will have to go through an operator activated regeneration. The process is quite straight forward; however, the vehicle needs to be parked for the process to take place. 

The process is done by a trained professional, who manually brings the engine to operating temperatures, initiating the regeneration process by activating the dash control. However, ensuring that the outlets are away from any flammable structures, trees, and vegetation is essential. This can also be done with the use of a DPF cleaner, a chemical additive that lowers the temperature required by the soot to be burnt off.

How to know If there is a Fault in the DPF

Generally, whenever the diesel particulate filter is full, a light appears on the dashboard, reminding the driver to manually clean out the ashes and leftover soot. However, if the light fails to go out, it might indicate that there is an issue with the DPF. It can be tricky to figure this out, however, if the light hasn’t gone out in a while, it could be an indicator of a faulty DPF.

Can a Vehicle Run Without a DPF?

Even though DPFs play a crucial role in the exhaust systems of diesel vehicles, many car owners may want to avoid the headache of cleaning these devices or having them installed. However, vehicle guidelines strictly advise against having the DPF removed, as it can land you in legal trouble with the Ministry of Transport (MOT). Moreover, the soot produced by the engine will have a callous effect on the environment as well. 

If you drive your car without a DPF on UK roads, you could potentially face a fine of around £2000-2500. Therefore, having one installed for your vehicle is the best course of action.


Despite seeming like an accessory, diesel particulate filters are an essential device that every diesel-powered vehicle must have. Understanding how these devices work and how to maintain them is necessary if you own a diesel vehicle. Considering the UK’s laws and the benefits that a DPF offers for the environment, having one installed for your vehicle is a must.

Find some of the best DPF cleaners for your vehicle at Turborevs and take your car’s performance to new heights.

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