Vale Performance | Everything you need to know about diesel particulate filters
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Everything you need to know about diesel particulate filters

Everything you need to know about diesel particulate filters

Diesel engines produce a different range of pollutants than petrol-driven engines.

That includes far higher levels of nitrogen oxides, and cancer-causing compounds.

Particulates in air pollution can penetrate deeply into people’s lungs and blood stream, and one 2013 European study involving more than 300,000 people showed an increased rate of lung cancer where levels of particulate were higher.

They have also been lined to other heart and lung problems and DNA mutations.

Ever since the introduction of Euro 5 emissions standards in 2009, diesel particulate filters have been fitted to engines in all new diesel cars.

They help stop harmful particles getting into the atmosphere.

All cars designed to have a filter must have one when inspected for the MoT. A lack of a filter means an automatic fail.

What does a diesel particulate filter do?

It stops harmful particles being emitted into the atmosphere, capturing the particles in soot left behind by exhaust gases.

However, various faults can also mean filters become blocked. This stops an engine from running and it can leave you with a repair bill running into thousands of pounds.

The soot must be burned at high enough temperatures to create ash particles, which are smaller and can be expelled out of the system. This is called ‘regeneration’.

Use the correct oil and keep your car’s fuel tank at least a quarter full to ensure the filter functions properly. These filters can last up to 100,000 miles if cared for correctly.

How does ‘regeneration’ take place?

There are two types: passive and active.

Passive regeneration happens at higher speeds with the engine running at higher revolutions. Manufacturers recommend you drive your car at constant speed over 40mph for more than 15 minutes every few hundred miles to ensure this passive regeneration takes place.

If it doesn’t, your car’s computer will step in to prevent the filter becoming clogged. It will raise the temperature of the car’s exhaust gases to start the process, which will take around 15 minutes to complete.

If your car has a stop-start engine system, this will deactivate.

If the process is interrupted too many times, perhaps by lots of short, urban journeys, your diesel particulate filter light will activate.

What should you do?

Take your car out on a dual carriageway for 15 minutes of continuous driving to give your filter the chance to regenerate.

If you don’t and you ignore the warning light, others will come on and the car will go into a self-protecting mode to ‘limp home’ – avoiding more engine damage.

Your filter may get to the stage where it cannot regenerate and most be unclogged or replaced.


If your diesel particulate filter has become clogged or you would like some free advice on prevention, Eco Techs provides filter cleaning and diagnostics. Our skilled technicians are part of the DPF Doctor network. Find out more here.

To book your car in for DPF cleaning, or to find out more, call us on 07867 411153.

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