In-Depth Look At Diesel Particulate Filters


The right way to care for your vehicle's DPF

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Explaining Diesel Particulate Filters and How They Work

A diesel particulate filter (DPF) is a filtration device installed in a diesel vehicle's exhaust system to trap particulate matter such as soot and ash, which are present in diesel exhaust gases. This prevents the tell-tale clouds of black smoke that characterized older diesel vehicles. DPFs have been compulsory on diesel vehicles for sale in the US since 2007. When a DPF becomes saturated, it must burn off excess soot through a regeneration process and, periodically, it must be cleaned. Owners of normal gas-powered sedan, convertible, and crossover car types don't have to worry about DPFs; they are only found on diesel engines in certain trucks such as the diesel-powered Ford F-250 Super Duty and the Jeep Gladiator EcoDiesel models.

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What is DPF Regeneration and How Does A DPF Cleaner Work?

DPF regeneration happens automatically when the exhaust temperature becomes high enough and is sustained for long enough to cleanly burn off all the soot that's accumulated in the DPF. A completely clogged DPF cannot regenerate and must undergo a forced regeneration or be professionally cleaned. A diesel particulate filter cleaner can be added to the fuel to reduce the temperatures at which the soot burns and clears your DPF. These must be used only as directed in the instructions to prevent damaging the DPF.

A DPF regenerates in one of three ways:

  • Passive regeneration. This happens automatically if you do enough highway driving. Exhaust temperatures stay high for a prolonged period, completely burning off the soot. No lights illuminate and you don't even know it's happening. Diesel particulate filter regeneration frequency depends on the vehicle and many other factors.
  • Active regeneration. When an exhaust-mounted pressure sensor records a certain amount of backpressure, the ECU enriches the fuel mixture and raises exhaust temperatures to burn off the soot. A warning light alerts you of the condition and turns off once regeneration completes.
  • Forced regeneration. If these fail, a forced regeneration can be done. A specialist must connect the vehicle to a diagnostic scan tool that forces the ECU to initiate regeneration. Because of the rich fuel mixture, it can contaminate the oil and the vehicle will require an oil change and a new oil filter. Forced regeneration can damage a DPF if done incorrectly.

In addition to this, proper maintenance requires that a DPF be manually cleaned every six to 12 months in order to function optimally.

Problems With Diesel Particulate Filters That Can Prevent Regeneration

The main problems with diesel particulate filters have to do with clogging caused by excessive soot. Although a DPF will regenerate by itself for the most part, once it is clogged, it might require a forced regeneration or a proper cleaning. Sustained highway driving for at least 15 minutes should trigger DPF regeneration. But, what can prevent regeneration from happening?

  • City driving conditions can prevent regeneration
  • A too-short highway drive interrupts regeneration and unburnt soot remains
  • Not using engine oil with low ash and sulfur
  • A faulty exhaust-gas-recirculation valve or another emissions-control device
  • Another engine condition that requires attention first
  • Poor maintenance, like low or dirty oil
  • A fuel level below a quarter-tank full may prevent regeneration in some vehicles
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How to Clean A Saturated Diesel Particulate Filter

Enough use will eventually cause the accumulation of diesel particulate matter (PM) that cannot be burnt, such as ash. Regeneration will then no longer be sufficient to clear your DPF and adding DPF cleaner won't have any effect. So, you're stuck with a blocked diesel particulate filter, but how to clean it is the question: your best bet is to have it professionally cleaned. The specialist must inspect the system first to correct any faults to avoid a recurrence of the blockage condition. You can get many years of service out of a DPF that regenerates normally and is periodically cleaned and maintained.


Your DPF should remain reliable if you do a proper highway drive every 300 miles or so, stick to a proper maintenance schedule, and have it cleaned professionally periodically. It's very important to learn how to properly care for your DPF, as a new one will cost at least $2,000 and often well over $3,000 - and this does not include installation. There can be quite a big price differential between car types, but none of them are cheap. If you want to know how to avoid DPF problems, just follow the advice in this article.


Can’t I just remove my DPF to prevent problems?

No, it is illegal to remove your DPF, since all diesel cars sold in the US must have a functioning DPF to minimize exhaust emissions and adhere to EPA regulations.

Can I have an aftermarket DPF installed in my vehicle?

Yes, there are several suppliers that can install compliant aftermarket DPFs in the same location as your vehicle's original DPFwhen it's time for a replacement, often at a lower cost than the OEM part. They do not always have a price list on their websites, because there are so many different DPF types, so it's best to contact a few suppliers and compare prices.

How would I know when it’s time for a professional DPF cleaning?

If the DPF light comes on more frequently, even after a recent regeneration, there is too much diesel particulate matter trapped in the DPF that cannot be burnt off. At this point, the DPF requires professional cleaning. We advise professional cleaning every six to 12 months.

How long do diesel particulate filters last?

A DPF should last at least 100,000 miles, but many last longer with proper maintenance and periodic cleaning.

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