AdBlue & DPF
DPF
What is a DPF on a car?
CheckFuelPrices Editorial
Expert Written • 4 industry sources
A DPF, or Diesel Particulate Filter, is a device fitted to the exhaust system of diesel cars that captures and stores soot particles to prevent them from being released into the air. It has been a legal requirement on new diesel cars sold in the UK since 2009 under Euro 5 emissions regulations.
What a DPF Does
Traps harmful soot:
The DPF captures fine particulate matter produced when diesel fuel burns in the engine, preventing it from entering the atmosphere. These particles are linked to serious respiratory health problems.
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Part of the exhaust system:
The filter sits in the exhaust pipe, usually close to the engine where temperatures are highest. It works alongside the catalytic converter to reduce overall exhaust emissions.
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Mandatory on modern diesels:
All diesel cars sold new in the UK from 2009 onwards must be fitted with a DPF to comply with Euro 5 emissions standards. Removing it is illegal for road use.
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How the DPF Cleans Itself (Regeneration)
Active and passive regeneration:
When the DPF fills with soot, it burns it off at high temperature in a process called regeneration. Passive regeneration happens automatically on longer motorway drives; active regeneration is triggered by the engine management system at lower speeds.
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Short journeys cause problems:
Drivers who mostly make short urban trips may find their DPF never gets hot enough to regenerate fully. This leads to blockages, warning lights, and potentially costly repairs.
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Forced regeneration:
A garage can perform a forced regeneration using diagnostic equipment if the filter becomes blocked before it can clear itself. This is far cheaper than replacing the filter entirely.
DPFs and Your MOT
MOT failure if removed or blocked:
Since February 2014, a missing or visibly removed DPF is an automatic MOT failure. Inspectors also check for excessive smoke emissions that indicate a blocked or damaged filter.
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Illegal to remove for road use:
Removing a DPF to avoid regeneration issues is illegal in the UK. You could face a fine and your car will fail its MOT. The DVSA actively checks for DPF removal during inspections.
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DPFs and Diesel Running Costs
Diesel suits longer journeys:
If you drive mainly short distances, a diesel car with a DPF may cost you more in maintenance due to blockage issues. Petrol or hybrid vehicles are often a better fit for city driving.
Fuel costs matter too:
Diesel prices vary considerably across the UK. Keeping fuel costs down helps offset the higher maintenance demands of a diesel drivetrain — CheckFuelPrices shows live diesel prices at over 4,000 stations updated every 30 minutes.
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Sources
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