Diesel Particulate Filter (DPF)

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The manufacture of diesel engine had a major impact on the environment. The sales of diesel engines cars were increasing rapidly, and the governments had to introduce new legislation tackling the pollution created by diesel engines.

The diesel particular filter was first introduced in 2009 but some vehicles had them before this date.

What exactly is the DPF?

The DPF is located under your vehicle on the exhaust system. A diesel engine produces more soot than a patrol car. Therefore, the soot was considered bad for the environment. The role of the DPF is to capture the soot produced during the combustion process, discharging less harmful particles into the environment.

This sounds huge for diesel engines. Right? But, with the introduction of the DPF, came a lot of reliability issues with diesel cars.

DPF Blockage

A diesel car was still in favour of most people due to its fantastic fuel economy. People were still buying diesel cars for city usage, even after the introduction of DPF. Eventoght the benefits of the DPF were exposed making people still purchasing diesel cars, the drawbacks of the DPF were unknown.

The DPF requires to heat up to around 600 Celsius to function correctly and burn the soot collected.

For city driving, that figure is almost impossible to reach and as a result, the DPF gets blocked with soot and require forced regeneration or replacement. Which can be expensive.

The great fuel economy of a diesel car can no longer be beneficial to all individuals. A diesel car should be used for long journeys or frequent motorway driving.

For example, a diesel car with 50,000 miles that was used in a city compared to another diesel car with 110.000 miles of motorway and medium to long journeys.

Instantly an individual would think that because of fewer miles the car is better and more reliable. But think again, when it comes to diesel, things stand a little different. I would 100 % go for a diesel that was driven correctly despite the millage.

A diesel that is not driven correctly and at low RPM’S will have reliability issues due to carbon deposits on the injectors, DPF, turbo and other engine parts.

You might want to consider adding some DPF cleaner from time to time to help with the cleaning of the soot.

DPF Regeneration

The DPF regenerates itself when driving. It needs to get to a temperature of 400 to 600 Celsius and requires constant driving at 40 mph or above between 2000 to 2500 RPMs for 10 to 15 minutes.

It’s a pain, I know.

This procedure should be done regularly to avoid the DPF from blocking.

There are two types of regeneration, active and passive.

Passive regeneration happens when you drive your car above 40 mph. This is done by driving constantly at speeds of 40mph and above.

Active regeneration takes place when you don’t drive your vehicle at high speeds and the DPF needs to heat up to burn the soot trapped.

Regeneration can also be done by a mechanic in a garage. This is also known as a forced regeneration and should only be done when the DPF will not clean by self-regeneration. This is not advised, as air needs to travel under the vehicle to prevent the DPF from getting to hot and cause a fire. There are cases where it has happened.

If you drive your diesel car in a city, stop-start traffic, your exhaust will not reach the temperature to start the regeneration and if it starts, then interrupted, it will cause more issues.

I own a 2012 Mitsubishi l200 pickup with a DPF fitted. The car was previously owned by a family member who lives in a small town and drove the car from A to B, usually short distances.

When I brought the truck, I noticed the oil level was above the maximum level. I immediately changed the oil and discovered that diesel was getting into my engine oil.

After some research, I discovered the problem to be the DPF.


Because of short-distance driving, the engine would start the DPF regeneration but always interrupted by stopping the truck’s engine.

When regeneration happens, if the DPF is clogged up, the active regeneration cannot take place and extra fuel goes pass your bores getting into the engine oil. The same thing happened to my truck. The regeneration will start but immediately interrupted.

DPF is still important

Despite all the negative aspects, the DPF is still important. According to CBRAir pollution causes an estimated 29,000 early deaths in the UK and has annual health costs of roughly £15 billion.”

The World Health Organisation classifies diesel emissions as a class 1 carcinogenic the same risk category as asbestos.”

Even though some garages do offer services for removing the DPF, this is a big no, Because of the negatives impact on the environment, and us.

If your vehicle was manufactured with a DPF and it was removed, the car will not pass the periodical technical inspection (Known as MOT in the UK)

Removal of the DPF will make the vehicle illegal to use on the road.

Electric cars aren’t pollution-free; they have to get their energy from somewhere.

Alexandra Paul

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