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Mon to Fri 8:30 to 5:30 · Sat 9 to 12Unit 17b, Berry Hill Industrial Estate, Droitwich WR9 9AH01905 795547
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Diesel particulate filter showing the ceramic honeycomb inside

DPF guide

DPF cleaning or replacement: which does your car need?

Most blocked DPFs can be cleaned. A new filter is only the right answer when the ceramic is cracked, melted or soaked in oil, or when whatever blocked it cannot be fixed. A new DPF typically costs £1,000 to £3,000. An off-car clean costs a fraction of that and comes with printed proof it worked.

By Northbank Garage, Droitwich · Updated 9 November 2026

Verdict A

Clean it if

  • it is blocked with soot or ash
  • the camera shows the honeycomb intact
  • the cause has been found and fixed
Verdict B

Replace it if

  • the ceramic is cracked or melted
  • oil or coolant has soaked into it
  • the case or sensor fittings are damaged

What is inside a DPF, and why it blocks

A diesel particulate filter is a ceramic honeycomb inside a steel case in the exhaust. Alternate channels are closed at each end, so exhaust gas has to pass through the porous walls between them, and the soot stays behind.

Illustration, not to scaleGas flowSoot on the wallsAsh at the closed ends

The filter clears itself by regenerating: getting hot enough to burn the soot off. On a long run at speed that happens on its own. On shorter trips the engine control unit raises the exhaust temperature deliberately, which only works if the drive lasts long enough to finish.

Burning soot leaves ash behind, from the additives in engine oil. Ash does not burn. It builds up for the life of the filter, so a high-mileage DPF eventually blocks however many regenerations it gets. That is the point at which most garages quote a new one.

Your four options compared

OptionRemovesTypical UK priceBest for
Additive or on-car cleanerSome soot£99 to £200A light soot build-up caught early
Forced regenerationSoot, turned to ash£160 to £500Soot-blocked filters on lower-mileage cars
Off-car cleanSoot and ashPriced by vehicle, quoted firstAsh-loaded and badly blocked filters
New DPFEverything£1,000 to £3,000Cracked, melted or contaminated filters

Market prices: ClickMechanic and BookMyGarage, October 2026.

When cleaning is the right call

  • Blocked by short journeys. A car that rarely gets a long run never finishes its regenerations, and the soot packs in.
  • Ash-loaded at high mileage. The classic case for a new-filter quote, and exactly what a wash removes.
  • After a fault has been fixed. A failed sensor or sticking EGR valve stopped the filter regenerating. Once that is repaired, the filter just needs emptying.
  • Before an MOT on a smoky diesel. Since May 2018, any visible smoke from a DPF-equipped diesel is a major fault.
Control panel of the DPF cleaning machine at Northbank Garage
Our cleaning machine measures airflow before and after every clean and prints both figures.

When a new DPF is the only answer

  • Cracked ceramic. Usually from an uncontrolled regeneration, when an overloaded filter burns too hot.
  • Melted channels. The same cause, taken further.
  • Oil or coolant contamination. A leaking turbo seal, worn injector or failing head gasket can soak the ceramic. Washing will not get it out.
  • A damaged case or sensor fittings. Corrosion or impact damage to the steel housing.

Our camera inspection shows all of these before any cleaning starts. If the filter cannot be saved, we stop, send you the photos and talk you through the replacement options.

Fix the cause, or it will block again

A DPF rarely blocks on its own. Something stops it regenerating, or fills it faster than normal. Clean or replace the filter without finding that, and you will be back.

  • Mostly short journeys, with no regular longer run
  • A faulty pressure or temperature sensor giving the engine the wrong readings
  • A sticking EGR valve
  • Worn injectors or a turbo leaking oil
  • The wrong engine oil: DPF-equipped diesels need low-ash oil to the manufacturer's specification
  • Low additive fluid, on cars that use a separate DPF additive tank

That is why we diagnose before we clean.

Why removing the DPF is not an option

Fine, carup to£1,000
Fine, light goods vehicleup to£2,500
MOT, missing DPFchecked since 2014Fail

Some firms still offer to remove the filter and remap the engine. On a road vehicle it is illegal. Driving one carries a fine of up to £1,000 for a car and £2,500 for a light goods vehicle, and it can invalidate your insurance.

MOT testers have checked for a DPF since February 2014, and a missing one is a fail. Since 20 May 2018, visible smoke of any colour from a DPF-equipped diesel, or evidence the filter has been tampered with, is a major fault. We do not remove DPFs.

What an off-car clean at Northbank includes

  1. The DPF removed from your car, or dropped off by you
  2. A camera inspection of the honeycomb, with photos on request
  3. An airflow test as it arrived
  4. A high-pressure hot-water wash through every channel
  5. About 30 minutes drying in the machine
  6. A final airflow test, both figures printed, and the filter refitted with fault codes cleared
A filter going through the clean, 54 seconds.

The cost, side by side

New DPF, typical£1,000 to £3,000Part and fitting, depending on the car
Off-car clean at NorthbankPriced by vehicleRemoval, clean, test and refit. We quote before we start.

Questions

Will a cleaned DPF last as long as a new one?

A wash takes out the ash as well as the soot, so the filter starts again with its full capacity, provided the ceramic is intact and the cause of the blockage has been fixed. Cleaned filters are guaranteed, provided any fault that caused the blockage has been put right.

Is a cheaper aftermarket DPF worth it?

Pattern filters exist and quality varies. If you go that way, make sure it is made for your exact engine and comes with a warranty. If your original filter is intact, cleaning it is usually the better value.

Can a DPF be cleaned without taking it off?

Additives and on-car cleaning fluids can shift some soot. They cannot remove ash, which is why high-mileage filters treated that way block again.

Will the warning light go off after a clean?

We clear the fault codes and, on cars that need it, reset the DPF values with diagnostic software so the engine knows the filter is clean.

How long will I be without the car?

Car in, filter off, cleaned and refitted takes a day, and it is usually done the same day.

Sources: DVSA, Matters of Testing: diesel particulate filters· GOV.UK, MOT changes 20 May 2018· ClickMechanic DPF cost guide

A clean costs a fraction of a new filter. Find out if yours can be saved.

Book a DPF clean Call 01905 795547

The DPF Surgery is the DPF cleaning service of Northbank Garage.