Do I Need My DPF Cleaning?

DPF Cleaning - GAP Turbos

What is a DPF?

Diesel particulate filters are emission control devices designed to clean the exhaust emitted by the vehicles’ diesel engines. In a diesel particulate filter (DPF), exhaust gasses pass through the open end of a channel and at the opposite end is a plug that forces the gasses through the porous channel wall allowing the exhaust to escape through the neighbouring channel wall trapping as much as 90% of the solid particulate matter.

Many vehicle dealers imply that all that is needed to keep the DPF clean is to hit the vehicle’s “regeneration” button. While the regeneration cycle is necessary and will burn much of the accumulated particulate matter, non-combustible materials trapped in the filter will still be left in the DPF, this remaining residue creates back pressure that will eventually lead to increased regeneration downtime, loss of horsepower, reduced fuel economy, filter damage and ultimately engine damage.


How do I service my DPF?

Regeneration is only a temporary measure in cleaning the DPF and eventually you’ll need to look at a better solution. There are many sprays, fluids and additives which claim to aid the cleaning of the diesel particulate filter – however this is not a guaranteed service – they may help unblock a DPF, but if the DPF is clogged with Ash rather than Soot then it’s unlikely that they will help at all.

So if your DPF cannot be fully cleaned with these additives, your next steps are either getting it professionally cleaned or completely replacing the DPF which can be very expensive.


GAP Turbos Professional Cleaning Process

At GAP Turbos we have a standalone machine which cleans the DPF to extraordinary levels – with a 95% success rate. This is done by removing the DPF from the vehicle and placed into our DPF cleaning machine, and then a 5 stage cleaning process takes place;

  • First internal check inside the DPF with an endoscope camera
  • Clean the DPF via a chemical solvent flush
  • Warm water de-greasing flush
  • Warm air dry
  • Final internal check the DPF with an endoscope camera

This process can be done by just sending your DPF to us once it’s removed from the vehicle – we can arrange free collection of the unit and then delivered back to yourself free of charge all for £100.

Alternatively if you are local, we can remove the unit from your vehicle, clean the DPF and fit it back on to your vehicle (in our in-house Birmingham workshop) for only £175. If we do fit the DPF back on to the vehicle we also do some additional checks;

  • Fault code checks
  • 10 mile road test

Find out more about our process here

Should I replace my DPF?

Having your DPF professionally cleaned restores the unit to pretty much its original state and it’s a much cheaper option than purchasing a brand new DPF for your vehicle(as this could cost more than £1000 to replace). We cannot state how long the DPF should last once it’s been cleaned, or until you need to do it again – as it depends on driving styles, different vehicles and the journeys that the car is doing, however our cleaning services comes with a 12 month ‘no quibble’ guarantee.

Ultimately, the choice is yours – however we believe our DPF cleaning service is extremely good value at only £100, rather than having to replace the unit which could cost you 10x the amount we charge for cleaning it.



If you would like to discuss this in further detail, or arrange your DPF to be cleaned please contact us on 0121 459 8170 or email us on

Posted in DPF

Diesel particulate filters DPF

DPF Filters Smog

DPFs reduce diesel soot emissions by 80%

The exhaust emissions standards for new cars have effectively required fitment of a DPF in the exhaust of diesel cars since 2009 when the ‘Euro 5’ standard came into force. In fact, many cars registered before 2009 will have had one fitted too in anticipation of the change in standards.

Standards aim to deliver an 80% reduction in diesel particulate (soot) emissions but the technology’s not without problems – AA patrols are regularly called to cars with the particulate filter warning light on indicating a partial blockage of the filter.

Even if your driving isn’t mainly urban/stop-start, changes to driving style may be required to keep these systems working properly.

If you’re buying a new car and plan to use it mainly for town-based, stop/start driving it would be wise to avoid a diesel car fitted with a Diesel Particulate Filter (DPF) because of the possible hassle of incomplete ‘DPF regeneration’.

dpf warning light

dpf warning light

How do they work?

Diesel Particulate filters (DPF) or ‘traps’ do just that, they catch bits of soot in the exhaust.

As with any filter they have to be emptied regularly to maintain performance. For a DPF this process is called ‘regeneration’ – the collected soot is burnt off at high temperature to leave only a tiny ash residue.

Regeneration is either passive or active

Passive regeneration

Passive regeneration takes place automatically on motorway or fast A-road runs when the exhaust temperature is high. Because many cars don’t get this sort of use vehicle manufacturers have had to design-in ‘active’ regeneration where the engine management computer (ECU) takes control of the process.

Active regeneration

When the soot loading in the filter reaches a set limit (about 45%) the vehicle’s ECU will initiate post combustion fuel injection to increase the exhaust temperature and trigger regeneration. If the journey is too short while the regeneration is in progress, it  may not complete and the warning light will come on to show that the filter is partially blocked.

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.

Symptoms of active regeneration

During active regeneration you may notice the following symptoms:

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

If the regeneration is unsuccessful due to an insufficient driving cycle the extra fuel injected into the cylinders will not burn and will drain into the sump.  As a result, oil quality will deteriorate and the level will rise.  Most DPF equipped engines will have an oil quality/viscosity sensor but it is important that you check that the oil level does not increase above the maximum level on the dipstick as diesel engines can run on their own oil if the level is excessive – often to the point of destruction.

If you ignore the DPF warning light and keep driving in a relatively slow, stop/start pattern, soot loading will continue to build up until around 75% when you can expect to see other dashboard warning lights come on too. At this point driving at speed alone will not be enough and you will need to take the car to a dealer for ‘forced’ regeneration.

Forced regeneration

Forced regeneration  is required where `Active` regeneration criteria have not been  met or where soot levels have increased within the DPF to a point where normal regeneration cannot be performed: typically around 70% soot loading.  At this point the vehicle will enter a ‘restricted performance’ mode to prevent further damage.  If left the soot loading will keep rising.

At this level of soot loading a diagnostic tool must be used to force regeneration. Above around 85% soot loading regeneration can no longer be performed on the vehicle and the DPF will need removing to be cleaned or replaced.

What can prevent normal regeneration taking place?

  • Frequent short journeys where the engine does not reach normal operating temperature
  • Wrong oil type – DPF equipped cars require low ash, low sulphur engine oils
  • A problem with the inlet, fuel or Exhaust Gas Recirculation (EGR) system causing incomplete combustion will increase soot loading.
  • A warning light on or diagnostic trouble code logged in the engine management system may prevent active or catalyst regeneration
  • Low fuel level will prevent active regeneration taking place. As a general rule ¼ tank is required
  • Oil counter/service interval – exceeding the service interval may prevent regeneration
  • Additive tank low or empty – if the vehicle uses Eolys™ additive a low level may prevent regeneration.

Expensive repairs

If you continue to ignore warnings and soot loading keeps increasing then the car won’t run properly and the most likely outcome will be that you will have to get a new DPF costing at least £1000 plus labour and diagnostic time.

The ash residue which remains after successful regeneration cannot be removed and will eventually fill the filter.  DPFs are designed to last in excess of 100,000 miles but, if the vehicle is operated correctly, many will far exceed this mileage.

DPF additives

The most commonly fitted type of DPF has an integrated oxidising catalytic converter and is located very close to the engine where exhaust gases will still be hot. This heat means that passive regeneration is more likely to be successful.

Some models, across a wide range of manufacturers, use a different type of DPF which relies on a fuel additive (Eolys™ fluid) containing Cerium (III) Oxide. Cerium ignites at a lower temperature and adheres to the soot particles meaning regeneration can occur at a lower temperature.

The additive is stored in a separate tank next to the fuel tank and is automatically mixed with the fuel whenever you fill up. Only very small quantities are used so a litre of additive should treat around 2800 litres of fuel – enough to cover 25,000 miles at 40mpg.  It lasts about 70000 miles and is replenished during a service – at extra cost.

You will have to pay to get the additive tank refilled at some time in the car’s life – expect to pay between £150 and £200 including fluid and labour

Don’t be tempted to ignore a warning light showing that the additive tanks need refilling.  It’s absolutely essential this tank is refilled as without it regeneration is unlikely to be successful and a new DPF may be needed – at significant cost.  Fuel consumption can increase as a result of failed regenerations too.

Check the handbook

If you buy a car with a DPF it’s important to read the relevant section of the vehicle handbook so that you understand exactly what actions to take if the warning light illuminates and how, if at all, your driving style may need to be adjusted to ensure maximum DPF efficiency and life.

In most cases there is only a relatively short time between the dpf being partially blocked and becoming so blocked that it requires manual regeneration.

AA experience

We’re seeing some evidence of DPF systems failing to regenerate even on cars used mainly on motorways.

On cars with a very high sixth gear the engine revs may be too low to generate sufficient exhaust temperature for regeneration. Occasional driving in a lower gear to maintain around 2,000rpm should be sufficient to burn off the soot in such cases (refer to the vehicle handbook).

DPF regeneration will be initiated by the ECU every 300 miles or so depending on vehicle use and will take 5 to 10 minutes to complete. You may notice other symptoms and a puff of blue smoke from the exhaust, similar to an engine burning oil, when the process is complete.

There’s no evidence in AA breakdown data that the problem’s going away – newer car models seem just as likely to suffer DPF problems if not driven ‘correctly’ as those built when DPF’s were introduced.

Removal is not a legal option

It is suggested from time to time that the answer to failed DPF regeneration is get the DPF removed from the exhaust system rather than pay to get it repaired/renewed.  Indeed there are companies advertising just such a service including reprogramming of the engine management software, but is it legal?

DPFs are fitted to meet European emissions regulations designed to reduce vehicle emissions of particulate matter (soot) associated with respiratory disease and cancer.

According to the Department for Transport, it is an offence under theRoad vehicles (Construction and Use) Regulations (Regulation 61a(3)) to use a vehicle which has been modified in such a way that it no longer complies with the air pollutant emissions standards it was designed to meet. Removal of a DPF will almost invariably contravene these requirements, making the vehicle illegal for road use.


You must notify your insurer if the vehicle is modified but such a modification could in turn invalidate any insurance cover because it makes the vehicle illegal for road use.


From February 2014 the inspection of the exhaust system carried out during the MOT test will include a check for the presence of a DPF. A missing DPF, where one was fitted when the vehicle was built, will result in an MOT failure.

With an original equipment DPF removed from the exhaust the car may or may not pass an MOT smoke test – a Euro V (September 2009 diesel) is more likely to fail than one designed to comply with earlier emissions standards.

Information taken from the AA website

BMW is working on a quad-turbo engine.

BMW Quad Turbo

BMW is working on a quad-turbo engine, says Autocar.

The company offers a tri-turbo in the X5 xDrive50d M Performance and the M550d, adding an electrically driven turbocharger for extra low-end boost pressure.

To make it a quad-turbo, BMW would add another electrically driven turbo, or could simply add a second bi-turbo to the diesel inline-six.

The quad-turbo inline-six diesel engine is expected to debut in the M750d 7-series sedan in 2016,Autocar says. The engine could develop more than 400 hp and 590 pounds-feet of torque (about 600 newton meters).


Exclusive offer for Automotive trade

Automotive Trade Offer Cars

Are you in the automotive trade?

Exclusive offer of NO QUIBBLE guarantee for one year from purchase.

All you need to do is purchase a turbo from GAP Turbos, fit it following the instructions and keep the proof of purchase .

If for any reason the unit develops a fault, send it back and we will honour the guarantee.