A diesel particulate filter traps the soot from your exhaust and burns it off when the exhaust gets hot enough — a process called regeneration. If you do around 10,000 miles a year with plenty of motorway driving, that generally takes care of itself. But with high-street driving, school runs and shopping trips the filter never reaches the 350°C it needs, and soot, carbon and ash build up until the light comes on.
Cleaning the filter costs a fraction of a replacement DPF, and you keep the original part. If the light is on, the sooner it's looked at the better — a filter left to block solid is far harder to bring back.
How we clean a DPF
We remove the DPF from the vehicle and connect it to our MET Clean DPF cleaning machine, which flushes it through with water and air, with chemical cleaning agents where needed, to remove all the built-up soot, carbon and ash. Ash in particular can't be removed by regeneration or by additive-in-the-tank products — it has to be physically washed out, which is why the filter comes off the car.
Why it happens
Modern engines are designed with lean-burn technology to bring emissions down, which in some cars means four different fuelling strategies based on throttle position, engine speed, road speed and a host of sensors and flaps. Combine that with long service intervals and the short, stop-start driving most of us do, and carbon builds up throughout the engine and exhaust — increased fuel consumption, poor running and, eventually, components that disintegrate. We clean these parts to bring the engine back to correct operation.
For businesses and other garages
We're a MET Clean Authorised DPF Specialist, using Tunap cleaning products that we settled on after years of testing what's on the market. We're happy to extend the service to fleets and to other garages that don't have the equipment themselves — call or contact us to find out more.
Frequently asked questions
Can't I just take it for a long drive?
A motorway run can clear soot if the filter is only partially blocked and the car can still regenerate. It does nothing for ash, and once the light is on most cars have already stopped trying. It's worth a go early on, but don't leave it weeks.
How long does a clean take?
Usually a day — the filter has to come off, be cleaned and dried, and go back on. We'll confirm when you book.