Hypermiling Top Tips: Top 5 causes of blocked / Failed DPF diesel particulate filters


In light of the recent scandal revolving around the VW diesel #emissionsgate, diesel cars are firmly in the spot light for all the wrong reasons. Sure, diesel cars use less fuel, save us money at the pumps and offer comparatively more torque than their petrol cousins but what many people fail to think about is the dreaded DPF filter.

DPF filters are ceramic and fine mesh filters which clean diesel exhaust gases of nasty particulates and soot. They are a vital part of any modern diesel engines but can very quickly wipe out any benefits of diesel car ownership.

We’ve done a lot of articles around how DPF filters work and how they are cleaned but very little on the main causes of DPF diesel particulate filter issues, so here are our top 5 causes of DPF issues.

Faulty EGR

EGR (exhaust gas return) valves are designed to reduce nasty emissions by recirculating waste exhaust gases back into a diesel engine. They are vital in reducing nitrous oxide (NOx) emissions however when they do wrong they can cause all manner of issues.

EGR valves reduce the available oxygen in the cylinder, this in turn increases the production of diesel particulates (fuel which has only partially combusted). A faulty EGR valve will increase the amount of particulates produced by the engine, causing your DPF to become blocked quicker than usual.

Find out more in our EGR Valve Frequent asked questions page

Using the Wrong Oil

Most vehicles manufacturers specify a low SAPS / Ash oil. Low SAPS oils are specifically designed to be low in Sulphated Ash – a by-product of diesel combustion that causes the DPF “mesh” filter to become prematurely blocked. If in doubt we suggest that your oil changes with the recommended oil type for your vehicle. An oil change is much cheaper than a DPF regeneration… trust us!

If you’re looking for low SAPs oil and are handy with the spanners then why not change the oil yourself. Amazon has a great selection of engine oils at prices to make your local grease monkey blush

Faulty / Failed fuel Injectors

Until recently faulty fuel injectors have been a topic that’s flown under the radar when looking at causes of blocked DPF filters. We were contacted by a frustrated motorist who experienced issues with his DPF blocking on a regular basis. The root cause was finally diagnosed as a faulty fuel injector providing too much diesel fuel into the delicate air / fuel mixture. This excess fuel caused the car to run rich with the resulting excess soot clogging up the filter.

Faulty Turbo charger

A faulty turbo charger can cause havoc for a modern diesel powered car. Anything to upset the delicate air fuel mixture causing your diesel engine to belch out even more of the nasty black soot than it already does. A faulty turbo charger may also leak oil huge quantities of oil into the fuel system resulting the DPF being drowned in a sea of engine oil.

Short journeys

The start stop nature of urban driving is one of the biggest reasons many drivers experience blockage issues. Short journeys, low speeds and the start stop nature of driving built up areas can make it near impossible to replicate the conditions needed for an active or passive DPF regeneration.

Let’s hear from you!

If you’ve been one of the many motorists effected by DPF failures and blockages we’d love to hear from you, please leave a comment below or get in touch via out contact page.

Read more on DPFs below:


Karl is the editor and owner of this glorious website. He currently writes for numerous environmental websites, producing content for the greater good. His experience in graphic design, Wordpress and all things automotive have helped sculpt Hypermiler.co.uk into its current form from very humble beginnings. He has numerous IT qualifications, a red belt in Taekwondo and likes craft Ales. Get in touch via our Contact Page

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20 comments on “Hypermiling Top Tips: Top 5 causes of blocked / Failed DPF diesel particulate filters
  1. richard says:

    I spent £3500 fixing the problem with my particulate filter on my Audi A4 S Line back in 2012 – 13. Can anyone tell me whether the emissions computer software would of caused this problem to exsacerbate?

    In other words, is it likely I can receive compensation after spending £3500 to resolve an issue on the car that may have been caused in part, by the emissions scandal (software).

    Many thanks


    • Paul Anderson says:

      Very unlikely as the emissions ‘scandal’ was NOx related. High levels of NOx indicate high combustion temperatures. These are ideal conditions for DPF regeneration. It’s a strange saga this NOx business. We need high combustion temperatures to reduce CO (not CO2), HC and particle emissions. But high temperatures do slightly increase NOx emissions.

      A further suggestion: avoid supermarket diesel completely. I use BP Ultimate exclusively and I have not yet experienced DPF problems.

      • Mark kerr says:

        Yes it is down to the soft ware down load Audi done under the recall the same thing happened to my father after just doing a 12.000 pound rebuild on his 4×4 skoda superb 170 I found this out because I’m a qualified technician I done a software check on the car and found the that software that Mervyn Stewarts done on Boucher road in bekfast did have A working EGR OR O2 SENSOR THAT CAUSED THE DPF TO BLOCK UP IN UNDER 5 MONTHS I HAD JUST CHECKED THE DPF BEFORE THE RECALL AND IT SAID O.O GRAMS OF SOOT TOTALLY CLEAN IN OTHER WORDS I CHECKED THIS REGULARLY BEFORE RECALL THE LOSY ALL POWER WHEN WE WENT TO MERVYN STEWARTS SKODA TO PICK IT UP THEY ALSO TOLD THE BRAND SKODA WARRANTY THAT IT NEEDED A NEW 02 SENSOR AND WHERE TO FIT A NEW ONE BUT WHEN WE PICKED THE CAR UP THE DATE ON 02 SENSOR WAS 05/09 it should 05/18 as brand new would had this date THat was still the original sensor in it they stole parts from the car because it had so much spent on it all date be on all parts dont trust mean dealers I also have photos before and after to prove that Mervyn Stewarts skoda owed by Stephen Stewart being investigated with prove of theift sabotage and fraud

  2. Dacia are one of the worst companies I have ever had the misfortune to deal with . I will never deal with this odious bunch of liars again!

  3. Tom says:

    I have had nearly a year of DPF alarm issues on my 4 year old CR-V. It is a great car other than this. It all started to appear after I had my first MOT and when the dealers suggested I add a DPF fuel treatment and prior to this I changed jobs also (less travel time). Each time the alarm comes on, the dealers have had to perform a regeneration, £90 a go and basically told me to take the car out on longer drives. After the fourth time requiring a regen, I complained – I had already complained after the second time – all HONDA said was that my driving style has caused the issue, not a technical fault and they recommend changing the DPF – shocking. They have basically washed their hands of the matter.
    I am now getting a deep clean at Halfords so I was hoping this would stop the alarm coming on but after reading you’re article I am concerned.

  4. Karl Radune says:

    VW Jetta dpf alarms for soot are NOT triggered by a mass flow sensor or any sensor. It’s a computor generated warning light at the warranty mileage limt 80000 miles. I pulled mine for regeneration myself. The dealer told me it was 85 percent full and wanted $4200 to replace it. I paid $300 for cleaning/regen. The before and after wieght showed it @ under 40 percent full. VW and the dealers are cheating people for uneeded built in repairs.

  5. Karl Radune says:

    I forgot to mention that after reinstalling the dpf you have to use a scanner to reset the milage counter to zero. Furthermore VW doesn’t tell you the computor won’t accept a miles reset without a forced manual regen even though the dpf was professionally cleaned. Again no sensors just a computor program to scan the VW Jetta owner

  6. tiberiu says:

    Problem with DPF???? God it gets on my nerves. 4 months ago had enginne light on board with vsc and trc lights on. i own a toyota avensis 2.2 d-cat from 2007. so i take the car to clean the dpf as the force regen didn’t work. the guy takes it down and clean it and the it shows me the core inside was melted parts of it. he said that happened because of too many force regenerations from previous owners. so needed to be changed. so i put a brand new dpf on it and now after 4 months my lights are on again. i just hope is just blocked and with a force regen i will get away with it. so DPF = the car owners’ nightmare!!!!!! Tomorrow i will try to book a force regen. the problem is that the oil level has raised in a bit over maximum limit wich indicates attempted regenerations not completed. that was my fault for driving short journeys. i am thinking of selling it and getting myself a petrol car. problem of dpf fixed in this way! 🙁

  7. tony stebbing says:

    2011 Jaguar XF driven for 66,000 miles until 1 May 16 with no problem, until engine fails. JLR contribute 50% of replacement engine. When engine replaced smoke from exhaust. DPF blocked after a few days JLR replaced DPF, short time after DPF blocks again and now JLR state the cause of fault is the way the car is driven. Refuses to state what work they carried out on exhaust and only give list of parts. Car remains in dealership as at the 26th Jan 17 where it was transported by JLR.
    Any advice would be welcome as I can see this matter ending up in court

    • Karl says:

      Hi Tony

      How long in between a replacement DPF and it blocking again?

      I suspect that there is an issue with the engine which is causing excess smoke. The problem will be proving this.

      Most certainly also ask the question on a Jaguar owners club forum. They may be able to help you further.

      Good luck and let us know how you get on.

      Cheers Karl

  8. Jeff says:

    I still don’t understand how a type of oil can clog a dpf…..unless the oil is getting burned and sent down stream and thus clogging the dpf. Would there be any other reason how it would become clogged other then the reasons listed….i.e., short drives.

  9. Daniel says:

    I have a problem with a Nissan qashqai 2013 I brought it seven months ago from Arnold Clark I took it in for a service because it was due and it went into limb mode on the way there I told them the situation. I picked the car up and they said the plastic air intake pipe had split that’s why it is doing it now I have fixed the problem and the car still doesn’t work I took it to a different garage for them to tell me that the dog is blocked and this could coat me alot of money now where do I stand do I complain to the dealer or to Nissan the car has only done 54000 miles and I drive long distances anyone able to help

  10. Janet Waterworth says:

    I have a problem with my Seat Altea 1.6 ecomotive. I had the upgrade done at the end of march, i didn’t know it was voluntary and i certainly wish i had never had it done.

    I was speeding up the slip road onto the motorway when the car suddenly lost power and the dash board lit up like a Christmas tree with fault lights. I took it to my independent garage and he initially diagnosed a senor fault, once changed the software then says there is an issue with the turbo. We had the turbo replaced. The car then faulted on the particle filter. The mechanic cleaned the filter and reset the system. Still the car runs in limp mode. My mechanic printed out the fault log which is showing the tolerance on the emissions is +/- 50 and mine is running at 75. He gave me the car back still running in limp made as he is saying the software is conflicting and it needs to go back to seat.

    I have taken the car to the main dealers that did the upgrade on the software. They initially found a sensor fault, for which they are charging me £210 to replace and now they have come back and said the turbo is faulty. Any one see a pattern here.

    I have just spoken to the garage and explained the turbo is new (they have all the receipts if they bothered to look)and advised what my normal mechanic has done, only for them to say, “He obviously didn’t know what he was doing”.

    I’ve not had my car for over 6 weeks now. Has anyone else had a problem like this where the software is conflicting ?

  11. Nigel says:

    Ford galaxy 2.0 reg 61
    100.000 miles had 3 regens.comes bake on within a week,
    Doin short journey,
    AA been out and shows dpf 52% down then to 9% but comes back on ??????

  12. Hazel Smith says:

    I have just recent bought a 2012 Citroen C4 in Spain. Straight away I had problems which required the particulate filter to be changed (expensive) then not 2 weeks later one of the fuel injectors has packed up….massively expensive and I’m now worried this will set off a chain of faults.

  13. Dan says:

    Laguna 2 1.9dci 2006 face-lift. Great car to drive, however within a week of purchase the dpf light came on. Dpf Pro cleaner did the trick, as did taking her for a boost up the motorway but with lot of start stop driving the problem is ongoing. We have removed and pressure washed it, passed mot despite the light on and check ignition on the dash. Renault want £870 plus vat for a new dpf. Wish we had been warned before buying this heap of frustration. Such a shame as its otherwise not a bad car. Now new mot rules will pickup on dpf removal, the only solution for some diesel owners. Back to the oldskool for me now going to run an older diesel on veg oil & forget this costly nonsense.
    Dpf car never again! We need a common sense website that advises which cars to buy /avoid.

  14. James Gribble says:

    My husband uses a Clio for instruction and has had several problems with the DPF. It is now going back in for the 3rd time. It is not even 3 years old. If he takes a student to test and the light is on the examiner will not take the car out. Renault keep saying about driving style and where he gets his petrol from. This is getting ridiculous. He had a Clio before exactly the same model and had no problems. The dealership do not seem to get it that this is a business tool !!

  15. Jas says:

    Bought used Nissan Qashqai 2014 J11 1.6 Diesel from Nissan dealer, got DPF problem now. Car under nissan extended warranty, Nissan dealer tried regen and it failed and they charged £275 for failed regen. Dealer suggested to replace DPF for around £1500+. I denied and they returned my car without fix.
    When purchased in 2016, it was on 42k miles and now car is on 66k miles. I drove almost 24k in 1.5 years. They are saying I dont do enough miles. Local garage for DPF cleaning asking for £700. Car has completely lost power and doesn’t move at all. Currently getting quotes from local garage. Please advise.

  16. Mark kerr says:


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