Information update – Diesel particulate filters DPF

Diesel particulate filters (DPF)

Looking to buy a diesel car?  Here’s what you need to know.

You might have heard about problems that motorists have experienced with diesel cars where a diesel particulate filter has led to costly repairs.

We’ve taken calls from motorists on this issue in the past, and have gathered advice from car manufacturers.  The good news is that this is a rare problem and there are simple steps that drivers of modern diesel cars can take to ensure trouble-free motoring.  Take a look and make sure that you go into your new car purchase armed with the facts.  And, if in doubt, ask your dealer who can talk you through the information.

Holly McAllister – Head of Customer Service and Quality


Now making up around 50% of all new cars sold, diesel cars have risen in popularity, particularly because of their fuel economy and lower running costs.

To reduce emissions, diesel cars are fitted with a diesel particulate filter (DPF) – something that filters and catches soot particles.  Most DPFs will automatically clear as they’re used but on rare occasions, in specific circumstances, they may get blocked and require manual cleaning.

In normal use, a DPF cleans or regenerates itself by reaching a sufficient temperature to convert carbon particles into CO2 and most drivers will never have to do anything other than drive normally to regenerate a DPF.

However, in a small number of cases, perhaps due to a car being used solely for short journeys or as a result of certain driving conditions, this recharging cycle hasn’t fully completed.

However, technology and strategies are advancing all the time to widen the opportunities for regeneration in a wider range of conditions, so the advice we give motorists who own a modern diesel car (generally DPFs have been fitted to vehicles from 2009 onwards) is to check your handbook for advice on DPF recharging – different cars have different requirements – and to act if any warning lights do show.  If a greater problem arises as a result of a DPF failure, repair work may not be covered under a warranty, if guidelines have not been adhered to.

If in doubt, whether you own a diesel or are considering buying one, speak to your local dealer.  All main dealers are trained to advise people on the right car for their needs.  Car manufacturers have all issued recent guidance on DPF recharging and, already, we’re seeing a drop-off in calls to the advice line as people are becoming more aware of this emissions-reducing technology.

Diesel cars & DPFs – some facts and figures:

  • Around 50% of new cars sold are diesel models.
  • Only 24% of all mini and supermini cars (those most associated solely with town driving) are diesel.
  • Most DPFs regenerate without any need to change driving style
  • Regeneration of a DPF will take place at any speed, as long as the optimum DPF temperature is reached.
  • A warning light will display if there is an issue. Consult the handbook or your dealer for specific advice.
  • Regeneration only has a 1% negative impact on fuel consumption.
  • A DPF check and service regeneration, if required, is part of the regular service schedule – find your nearest dealer at: TMO Garage Finder

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