MOT DPF changes now expected in May 2018

Test update to come into force next year to combat flaws of the current visual DPF inspection requirement

MOT DPF changes now expected in May 2018
The current MOT is failing to identify many cases of DPF removal because it only includes a ‘visual inspection’ of the hardware. Image: Bigstock.

MOT changes designed to make it easier for testers to detect vehicles with failing or removed DPFs are expected to be introduced next year, the Department for Transport (DfT) has told GW.

From May 2018 the smoke test limit for Euro 6 and some Euro 5 diesels will also be halved.

In a statement obtained by GW, a DfT spokesperson said: “We are taking strong action to stop the removal of DPFs.

“We expect future changes to the MOT emissions test for diesel vehicles, due to come into force by May 2018, to make it easier to detect vehicles with failing or removed DPFs.”

Unfit for purpose

The DVSA say 1,800 cars have been caught without a DPF since 2014 but experts believe the number is much higher and suggest that the current MOT visual inspection is unfit for purpose.

While it is illegal for drivers to use a car with the DPF removed, it is not illegal for garages to take them out.

Some workshops are known to offer removal services with the claim that removal will improve the vehicle’s performance, or is cheaper than replacing the current DPF.

Removal services

Speaking to GW, head of research and development at Klarius Products, Doug Bentley said: “The reality is that the functional part of a DPF is a ceramic block inside a tough metal casing, it is brittle and can be drilled through and/or smashed, so the functional part of the device is removed and the casing is simply bolted back into the exhausts system.

“From the outside it looks like all is well.

“However, removing the filter element not only releases clouds of harmful soot but often the ceramic brick is also a catalytic converter, so harmful exhaust gases can also be released into the air too.

“If a new test can show-up when the DPF is an empty casing, not just missing from the system, then this practise of removal may stop, or reduce, which will be a good thing for the environment, the car’s engine and the customer’s wallet at the pumps.”

38,000 premature deaths

Diesel particulate matter is damaging to the heart and lungs and has been linked by The World Health Organisation to 38,000 premature deaths every year.

In a recent crackdown on test stations that advertise DPF deletion services, the DVSA issued serious warnings for testers and garages offering DPF deletion services.

Speaking earlier this year, MOT product manager at the DVSA, Danny Charles said: “Remember, the consequences of turning a blind eye to a missing diesel particulate filter – or worse, actively taking part in their removal – can be serious for an MOT tester.

“A vehicle that needs a particulate filter and doesn’t have one should fail its MOT.

“If you pass it knowing that it doesn’t have one, you’re harming the environment and committing fraud.”

DPF vehicle data

However, many argue that the DVSA needs to do more to make data readily available for testers.

Commenting on GW recently, technician David said: “DVSA really need to be clear about which vehicles are actually fitted with DPFs to ensure testers are also made properly aware of which vehicles they should be fitted to.

“DVSA have taken a back seat with the VMs and gaining technical information.

“It’s time they put their foot down and got it then pass it onto the test stations that need it to do the job correctly.

“I for one still don’t know which vehicles are supposed to be fitted with a DPF.

“I came across a Transit with no exhaust system on seeing only a tail pipe mounted at the exhaust manifold area, thinking that some clever trader had removed the DPF.

“I failed it, only to find later from Ford that they didn’t fit a DPF to that model of Transit.

“Testers have got the short straw here.”

Do you think more needs to be done to tackle DPF removals? Share your comments below.


  1. I would agree that testers need more exact information.
    When a tester fails a vehicle for this reason they are
    1)Accusing the owner of deliberately breaking the law
    2)Insisting that an expensive replacement is necessary.
    Before doing that exact information is essential.

  2. we as mot stations will have to foot the bill for equipment to check cats and vosa will not give us a price increase our set prices you know this will happen they dont care about the testers/ stations as long as they look good

  3. we test to 3.00 or 1.5 % on the later cars on the smoke test which is a fudge because if you look on the vin plate in a little square box will be 0.5. That was the maximum percentage that was allowed on the later cars and all should comfortably be inside this if properly maintained. Cars which have their DPFs removed sometimes creep inside but not often but have no problem with 1.5%. VAG group cars always pass as they don’t rev using a tiny amount of fuel to do nothing even ones with sooty tailpipes…I wonder if something was missing inside a dpf ???

  4. The dpf system is complex and can be simple to understand for someone who is trained . If for some reason the dpf blocks then the route cause of this needs to be fixed before any action is taken on removing the blockage .

    The biggest problem is the main dealers along with Halfords are clueless to this system and have no idea what they are doing.

    Get the problem looked at by a specialist and the truth is you won’t have any problems.

  5. Dint know why they have been so slow at bringing this out
    They have been testing ultra low emition trucks for years with a separate smoke tester !!!

  6. Bringing the smoke level down isn’t going to work it’s NOx emissions that need testing not smoke, if the exhaust system is less restricted and someone has tampered with the internals it would apear to be cleaner due to no soot build up within the CAT or DPF
    the main cars to fail a smoke test are those driven around town all day as the exhaust system blocks up over time.
    And as previously mentioned there are many vehicle manufactures that have fitted a DPF to one particular model and not another.
    Am I right in saying that NOx emissions are tested in Europe?

    • Nox is only produced at high combustion temperatures under heavy load so unless you have a way of replicating that how would you be able to test for nox?

  7. With regards to the statement below.

    “If a new test can show-up when the DPF is an empty casing, not just missing from the system, then this practise of removal may stop, or reduce, which will be a good thing for the environment, the car’s engine and the customer’s wallet at the pumps.”

    Does this person understand what and how a DPF works on a car? Maybe they are getting mixed up with the EGR valve with regards to economy. Also the first time Ive heard someone state that a DPF benefits a cars engine. Really like to here his explanation on that.

    ps. I do not agree with removal of the system myself.

    • Quiet agree Ryan. Lots of smoke and mirrors on this subject with many not really understanding what a dpf actually does, what effect this technology has on a vehicles long term reliability, and thats before the discussion regarding EGRs is dealt with. Where drivers warned of the cost of maintaining this technology when they purchased their vehicle ?

  8. The whole uproar about testing for soot particles is so fatuous.
    Ok Sir just drive for 5 miles at a steady 60 mph and all your troubles will be behind you!!
    In reality, spread your particles over the countryside ,but not on my garage forecourt.
    Have we all given up on reality? The only way forward is to ensure that when produced, the soot must be contained and disposed of in a controlled manner. I look forward to the mandatory introduction of a DPF cleaning and capture system that is recognised as safe and sensible.
    Money Save Service Centre Altrincham.

  9. i agree with Craig who said you would have to test the NOx. all cars with inside of particulate filter missing , would pass a mot test as it stands at the moment ?

  10. Whilst there is a big question mark over DPFs and as this issue attracts more attention so will the science behind it, costs and associated damage and costs. With DPFs being fitted since 2002 there are most likely millions of vehicles with ineffective or removed dpfs ! Why ? because the technology is flawed. Huge repair bills have been generated from this failed technology along with unexpected replacement dpf costs…with most owners never being notified that, A) it might happen & B) how expensive they are.

  11. Sorry but I can’t see simply reducing the smoke limits will make any difference to the problem of removed DPF’s. As someone said above all the time we’re testing VAG group cars that only rev to 2k or so NOTHING is going to fail.
    The only real answer is to produce kit that can test emissions (including NOX) whilst the car is being driven on a reasonable test route. But, for obvious reasons, that’s never going to happen. So all we get is brave talk which, although the intentions are good, isn’t going to change anything.

  12. It’s about time the manufacturers and the dealerships got there arses kicked because neither of them gave out the advice about the problems related to the dpf’s and the cost of replacement ..

  13. This problem it’s going to get worse. The software emissions “Fix” for VAG vehicles increases soot 3 fold. Three times the soot= three times the DPF problems.

  14. Hello. Why the hell they don’t comes with a proper solution of dpf? Why it’s costly to regenerate or fit a new one ? Why they don’t make it easy to replace the filter at low cost ? Is goverment trying to clean the air or cleaning driver’s pockets?

  15. There is only one cure, no Diesel engines. Until someone can produce a cleaner diesel burning engine the problem is not going away. Local running, low mileage vehicles will continue to block the DPF. Regeneration needs to be set to actuate at lower temperature and way before the filter becomes blocked. I carried out a clean on a Suzuki that went over 1000degrees inside the Filter. It got so hot it ignited the pressure sensor rubber pipe. Is there really a solution?

  16. I agree completely with the three comments above, In a nutshell it’s a European directive that had good intentions but ultimately it ended up costing unweary user’s, ( I know because my Daughter has just forked out £1500 for a new DPF on a 2012 Seat!).
    Why not make a filter cartridge that can be exchanged at service time like an Air, Oil,Fuel,Pollen filter is changed?
    Oh yeah, I forgot there’s no profit in that!
    Jaded opinion? yes, I have lost faith in the design resons behind some ‘new’ technology.

  17. Edit, I don’t agree with the comment by Ken, it appeared before my reply
    Diesel can work!!

  18. How can you test for nox since its only produced at very high combustion temperatures under heavy load? How would you be able to replicate that at a testing station? Simple answer is you wouldn’t .

  19. Dpf is Just another motoring con, the connection to lung issues is a tenuous as saying step ladders are responsible for broken necks ,yes if you sit of the back of my exhaust sucking the fumes up then you will die of lung issues otherwise in the real world you will defiantly die at some point in your life from something else and that’s a fact


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