Frequently Asked Questions

What Is A DPF?

A diesel particulate filter (DPF) is a filter; the filter itself consists of a ceramic or metal honeycomb structure coated with precious metals like platinum or palladium. These metals facilitate the oxidation of the trapped soot, resulting in a reduction of harmful emissions from diesel cars but because they only have a finite capacity, this trapped soot periodically has to be emptied or ‘burned off’ to regenerate the DPF.

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Why Does A DPF Become Blocked?

Over time, the trapped soot and particulate matter can build up in the filter, which can reduce its effectiveness. This can happen for a variety of reasons, including:

• Short trips: If you frequently take short trips in your diesel vehicle, the DPF may not have enough time to heat up and regenerate, which can lead to a build-up of soot.
• Low-quality fuel: Using low-quality fuel can increase the amount of soot produced by the engine, which can lead to a build up in the DPF.
• Faulty engine components, such as the fuel injectors or turbocharger, can lead to increased soot production. This is because these components help to control the combustion process, and when they are not working properly, more soot is produced. This, in turn, can cause the DPF to become clogged, leading to decreased engine efficiency and fuel economy. To ensure optimal vehicle performance and prevent further damage, it’s crucial to regularly clean the DPF. In fact, failing to do so can result in various issues, such as reduced engine efficiency and fuel economy, as well as a clogged DPF It’s advisable to clean the DPF every 80,000-100,000 miles or as per the manufacturer’s recommendation to prevent costly repairs and maintain performance.

Short journeys at low speeds are the prime cause of blocked diesel particulate filters.

Other things that are bad for DPFs include poor servicing and not looking after your DPF.

A diesel particulate filter on a poorly serviced car may fail sooner than a well maintained one, generally, they should last for 80,000 to 100,000 miles depending on your driving style.

It’s important you use the right type of oil as well – some oils contain additives that can actually block filters.

Performance modifications can damage a diesel particulate filter, as can using low-quality fuel and even running the car frequently on a low fuel level as the car may avoid DPF regeneration.

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How Do I Know If My DPF Is Blocked?

• DPF dashboard warning light is lit.
• Reduced fuel economy.
• Loss of power, reduced acceleration, lower speed etc.
• Engine smells acrid.
• Rough idling.
• Dirty / black exhaust emissions.
• Problems starting your vehicle.
• Your vehicle may suddenly go into 'limp-home' or 'restricted performance' mode.

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Can A Blocked DPF Ruin My Engine?

Yes.

• Reduced efficiency of the exhaust system
• Gas build up and higher temperatures can damage your engine
• Oil can carbonise in the turbo system, leading to engine damage
• Damage to your turbocharger

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How Do I Maintain My DPF Filter?

The best way to maintain a DPF is to make sure it’s fully able to regenerate itself when it’s full of soot (when the warning light appears).

Get your car flushed every 80,000 – 100,000 km with a proper chemical cleaning solution

There are two types of regeneration: passive and active.

Passive Regeneration

Passive regeneration occurs when the car is running at speed on long motorway journeys which allows the exhaust temperature to increase to a higher level and cleanly burn off the excess soot in the filter. So it is advised that drivers regularly give their diesel vehicle a good 30 to 50 minute run at sustained speed on a motorway or A-road to help clear the filter.

However, not all drivers do this type of driving regularly – which is why manufacturers have designed an alternative form of regeneration.

Active regeneration

Active regeneration means extra fuel is injected automatically, as part of the vehicle’s ECU, when a filter reaches a predetermined limit (normally about 45%) to raise the temperature of the exhaust and burn off the stored soot. Problems can occur, however, if the journey is too short, as the regeneration process may not complete fully. If this is the case the warning light will continue to show the filter is still partially blocked. In which case it should be possible to complete a regeneration cycle and clear the warning light by driving for 10 minutes or so at speeds greater than 40mph.

You will know whether active regeneration is taking place by the following symptoms:

• Engine note change
• Cooling fans running
• A slight increase in fuel consumption
• Increased idle speed
• Deactivation of automatic Stop/Start
• A hot, acrid smell from the exhaust

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Will I Fail My MOT With A Blocked DPF?

A blocked DPF will result in an MOT Failure. Removing a DPF is illegal, and will also result in a MOT failure.

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Can't I just replace my DPF?

A new DPF can be expensive, and you will still need to pay for removal of the old one, and refitting the new one.
We will return your filter to a 'like-new' state for a fraction of the price of new.

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Can't I Just Remove My DPF?

No - it is illegal to remove your DPF.

In 2009, legal emissions limits effectively made it compulsory to have a DFP fitted in diesel cars. It is illegal to remove your DPF, and will invalidate your insurance policy.

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Can I Use Cleaning Fluids To Clean The DPF Myself?

This might be a good short term solution - if you can't drive your car to a garage, this can help to get your car moving, but it will not fix the issue.

Our thorough DPF deep clean will remove the vast majority of the accumulated soot from your DPF, and will give your car many extra years on the road.

Don't waste money on a short-term temporary fix.

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Shouldn't A DPF Clean Itself?

Around every 300 miles, diesel engines 'regenerate' the DPF by increasing the temperature to burn off any collected soot particles. Some of the resulting ash collects in the filter, and in time the DPF becomes blocked with this accumulated ash, soot and carbon. At this point, running the vehicle will result in damage to the engine.

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DPF Trouble: Short Journeys At Low Speeds

If you make lots of short, low speed journeys, the inbuilt 'regeneration' process to automatically clean your filter will not be effective, leading to your DPF quickly becming blocked. Generally, drivers are advised to regularly drive on motorways at sustained speed for 10minutes to an hour, in order to let the vehicles automatic regeneration process work effectively.

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