Diesel engines are known for their power and efficiency, but they also come with their own set of challenges, especially when it comes to emissions. The diesel particulate filter (DPF) is a key component of modern diesel vehicles that is designed to reduce harmful emissions. But over time the DPF filter can become clogged, which leads to performance issues, an increase in fuel consumption, and, if left unchecked, damage to the engine. But what is a DPF? And how can you keep your DPF clean? We’ll answer all your questions and more below.

What is a DPF and what does it stand for?

Commonly referred to as a DPF, or DPF filter by some, the acronym stands for diesel particulate filter. A DPF then, is essentially a filter that stops exhaust particles from the combustion of diesel fuel escaping the exhaust system and getting out into the atmosphere. The DPF allows gases to pass through it while collecting solid matter such as soot and other small particulate matter. By capturing these elements, diesel vehicles release fewer harmful emissions into the atmosphere, leading to improved air quality and health standards. 

Why do DPFs get clogged?

DPF filters only have a finite capacity, meaning that with continued use they will eventually fill up and become clogged. To prevent this, diesel vehicles are designed to be able to clean the DPF themselves by burning off the built-up soot in a process known as regeneration. This regeneration process essentially burns off the build-up of soot collected by the filter. However, despite this ongoing cleaning process, DPFs can still get clogged.

The main reason that DPFs become blocked is when the regeneration process is not allowed to occur. This is usually due to taking lots of short journeys at low speeds, such as city driving, without ever getting the engine up to a high speed for a sustained period of time. The reason for this is that the DPF can only burn off the build-up of soot and regenerate during long periods of high-speed driving. That being said, using a diesel fuel additive with a DPF cleaner can allow the DPF to be cleaned, even at lower speeds.

DPF self-cleaning

Your vehicle’s DPF filter gets filled with particulate matter quite quickly. This is why engineers developed a self-cleaning system for the DPF known as regeneration or regen. This process burns off the accumulated soot and particulates that the DPF captures from the exhaust gases of a diesel engine. 

There are three types of regeneration:

Passive regeneration

Passive regeneration occurs naturally when a vehicle is traveling at speed for a prolonged period of time, such as on long highway journeys. This kind of driving increases the temperature within the exhaust system to a level high enough to cleanly burn off the excess soot in the filter, typically at temperatures above 350°C.

For regeneration to occur, three conditions must be met:

• There is enough diesel fuel in the tank (around a quarter of a tank or more).
• The vehicle’s oil and coolant is up to the correct operating temperature.
• The vehicle maintains a minimum speed of around  40mph for a 20-minute period.

While the DPF is designed to regenerate itself, it will not do so if the above conditions are not met. This is why frequent short trips and stop-and-go driving prevent regeneration and lead to a clogged filter.

Active regeneration

Active regeneration is a feature that some vehicle manufacturers have built into their vehicles to prevent the DPF from becoming clogged. If the exhaust temperature isn't high enough for passive regeneration, the engine management system can initiate active regeneration. 

Active regeneration works in a similar way to passive regeneration, but rather than the required temperature being achieved by driving, extra fuel is injected into the system to achieve this effect. This process happens automatically as part of the vehicle's ECU when the DPF filter reaches a certain soot threshold (typically around 40-45%). 

If you haven’t done any high-speed driving during this time, the ECU will automatically raise the temperature of the exhaust system by injecting fuel, allowing stored soot to be burned off the DPF. This doesn’t necessarily fix the problem though, as if the journey is too short the regeneration process may not be able to complete fully. 

Here are the signs to look out for if your vehicle is undergoing active regeneration:

• A change in engine sound
• The cooling fans are running
• Fuel consumption has increased
• A hot, unpleasant smell from the exhaust

Forced regeneration

Despite the active and passive regeneration systems, there are still situations when the DPF might become so clogged with soot that it doesn’t work properly. In these cases, your vehicle’s DPF will need to be forced to regenerate. A forced regen works in much the same way as a passive or active regen, but it requires telling the ECU to put the vehicle into the conditions necessary to regen without being on the road.

In a forced regen, the vehicle's ECU tells the engine to run in a way that increases exhaust temperatures to the level required to combust the trapped soot and particulate matter in the DPF. As this process requires accessing the ECU, it requires specialized diagnostic equipment. However, it's important to bear in mind that a forced regen should only be performed when it’s actually needed, as unnecessary regeneration can potentially damage the DPF.

Signs your DPF needs manual cleaning

DPFs typically last for 100,000 to 150,000 miles before they need replacing, but how quickly this will happen to you depends on a number of factors, such as your driving style and how much car maintenance you do. When your vehicle’s DPF gets close to this figure, you might start to notice some issues related to it being clogged, such as:

Reduced performance 

A clogged DPF can restrict the flow of exhaust gases from your engine, which can have negative effects on your car's power, acceleration, and fuel efficiency. You might notice a loss of power while driving or even a poor throttle response.

Increased fuel consumption

As performance goes down, the engine has to compensate by working harder in order to function. As fuel is the source of your engine’s power, working harder means it has to use more fuel than it otherwise would in order to operate correctly.

Exhaust smoke

If you notice black smoke coming from your exhaust pipe, that’s a good sign that your DPF filter isn't working properly. A healthy DPF traps soot and particulate matter, but when it becomes blocked, it can’t do this as effectively, leading to excessive smoke.

Check engine light

A clogged DPF will likely trigger the check engine light on your vehicle’s dashboard, signaling that there is a problem with the exhaust system. The ECU monitors the performance of the DPF and will activate the warning light if it detects excessive backpressure or insufficient regeneration. 

More frequent regens

As the DPF becomes more clogged, you might notice your vehicle starting regeneration cycles more frequently to try to burn off the accumulated soot. An increase in frequency indicates that the DPF is struggling to maintain its efficiency. Keeping the DPF clean helps maintain its ability to regenerate properly, which we will explain further down the page.

How to clean a DPF at home (with a DPF cleaner)

Regular cleaning of the DPF is essential to maintain your engine's performance, efficiency, and longevity. One of the easiest ways to take care of your DPF, reduce how often it needs to regenerate, and prevent it from becoming clogged is to use a diesel fuel additive which includes a DPF cleaner. Archoil’s Diesel Fuel System Kit contains two specially formulated products that can keep your DPF clean and much more:

The AR6400 Fuel System Cleaner works as a “deep clean” and contains powerful detergents that can remove even the heaviest build-ups from your DPF, while also cleaning your turbo and fuel injectors as well. The powerful chemistry of this additive is able to survive the combustion process and by utilizing the heat of the exhaust is able to remove built-up deposits and clean the DPF.

The AR6500 Diesel Treatment acts as a “maintenance dose” of DPF cleaner that can be added to your tank every time you fill up. It is the only product on the market that not only keeps your DPF, turbo, and fuel injectors clean, it also increases the lubricity of your diesel fuel and boosts its cetane rating by up to 8 points. Not only does this help to keep your DPF clean while you drive, but it also promotes better combustion, which leads to the formation of fewer deposits in the first place. Tests have shown Archoil’s diesel fuel additives to increase miles between regens by up to 46%, protecting the engine and preventing premature failure.

Using diesel fuel additives really is the best way to protect your entire fuel system and engine, leading to fewer visits to the mechanic and ultimately saving you money in the long run. Using these two products is all you need to ensure your vehicle’s fuel system is in the best health it can be. For more information on how to use the products, you can take a look at our  AR6400 and AR6500 user guides.

FAQs about DPF cleaning

What does DPF stand for?

DPF stands for Diesel Particulate Filter. It is a critical component in diesel engine exhaust systems, designed to capture and store soot and other particulate matter produced during the combustion process.

How often should a DPF be cleaned?

The DPF will automatically clean itself through a process known as regeneration. However, over time deposits will still build up on the DPF. To remove these it is best to use a diesel fuel additive that has a DPF cleaning component.

Can I clean a DPF while driving?

Yes, the DPF can clean itself while you drive through a process called passive regeneration. However, this only occurs when the exhaust temperature is high enough for a sustained period of time, such as when driving on the highway.

What is the best DPF cleaner?

The best DPF cleaner is one that can also clean the other parts of your fuel system, such as the turbo and fuel injectors. Archoil’s AR6400-D can do just that and has been proven to remove even the most stubborn deposits. Likewise, Archoil’s AR6500 can provide an ongoing maintenance level cleaning of your DPF while also boosting your fuel’s cetane rating and increasing its lubricity, giving even more benefits to your engine and fuel system.

What happens if I ignore a clogged DPF?

If you ignore your DPF warning light and allow it to become more clogged, your vehicle will suffer several issues, starting with engine performance issues and ultimately ending with damage to the engine. In severe cases, the DPF could become so clogged that it would need to be replaced, and this can be quite costly.

How much is a DPF filter?

The cost of a DPF filter varies depending on the make and model of your vehicle, but generally, it can range from $2,000 to $10,000, including installation. High-end or heavy-duty vehicles may have even more expensive DPFs. Because of the high cost of replacement, we recommend regular and ongoing maintenance using a DPF cleaner.

How long can you drive with DPF light on?

If your DPF warning light comes on, it’s an indication that the filter is becoming clogged and needs attention. You can usually drive a short distance with the light on, but it’s recommended to address the issue as soon as possible to avoid further complications. The easiest way to do this is to add a diesel fuel additive with DPF cleaning properties next time you fill up.

Can a blocked DPF cause turbo failure?

Yes, a blocked DPF can cause turbo failure. The increased backpressure from a clogged DPF can strain the turbocharger, leading to overheating, oil leaks, and eventual failure. The turbo relies on a free-flowing exhaust to function properly, and a blocked DPF disrupts this balance, potentially causing damage.

Conclusion

Cleaning your DPF is crucial for maintaining your diesel vehicle’s performance and longevity. By understanding the signs of a clogged filter, how your vehicle regenerates, and how using fuel additives can clean and protect it, you can keep your DPF in optimal condition, ensuring your vehicle runs smoothly and efficiently for years to come.

For more great vehicle guides and maintenance tips, take a look at our Resources page.