Diesel Particulate Filters: Everything You Need to Know About DPF Filters

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New diesel trucks already have DPF filters installed. But it can be worthwhile to install these filters on older diesel truck models as well, both for fuel efficiency and to prevent air pollution. And, regardless of a truck’s age, DPF filters are just like any other part: eventually, it gets worn out and needs to be replaced.

Figuring out how to make your DPF filter last, when to replace it, and how to install it can be tricky! After all, DPF filters are a complex, technical truck part. Fortunately, today we’re going to break down and address the top 12 most frequently asked questions about DPF filters.

Mytee Product’s Ultimate Guide to DPF Filters!

1. What is a DPF Filter?

DPF stands for Diesel Particulate Filter. Such DPF filters are devices that reduce toxic emissions (air pollution) from diesel exhaust. Specifically, these filters prevent solid particles that are harmful to breathe (i.e. soot), which are created by burning fuel, from leaving the truck and getting into the air. They also keep an engine more fuel-efficient by recycling the soot that gets caught and re-using it for fuel again.

DPF filter

DPF filters are a type of “wall filter,” and they’re typically made of ceramic, silicon carbide, or cordierite.

2. Where is The DPF Filter Located?

DPF filters are positioned within the exhaust system. The filter rests ahead of the NOx trap (also called the NOx storage catalytic converter) and exhaust pipe itself, but after the temperature sensor. Essentially, the DPF filter is the part of the exhaust system that’s closest to the engine.

3. How does The DPF Filter Work?

Diesel engines are internal combustion engines. The cylinders in the engine compress air with such force that the air becomes a dense gas– dense enough that it becomes superheated, igniting the diesel fuel. This creates a kind of “controlled explosion,” one in which most of the heat energy is changed into kinetic energy by the internal mechanisms of the engine (the physical motion of the piston and crankshaft), turning the wheels and powering the truck.

Image Source: Wikimedia

However, this explosion also releases excess gas and solid particles, an extra physical matter we call exhaust. The exhaust is eventually released through the exhaust pipe. But, before this happens the mixture of gas and particles flows through the DPF filter, where 90% of the particulates are trapped.

The temperature sensor, which sits between the DPF filter and the combustion engine, keeps itself aware of the engine’s temperature to regulate the soot “recycling” process (which requires a certain degree of heat to work).


The technical term for soot recycling is “regeneration.”

There are two types of regeneration: passive and active. Passive regeneration is when the soot burns and the heat becomes power naturally, which happens on long drives at the high speeds typical of the freeway. Active regeneration requires a means of burning the soot at a lower temperature. Essentially by heating the particles with an additional part or process: an electric heater or a mechanism that triggers second internal combustion (like an injection of fuel or pressurized oxygen).

This is called a catalytic combustion process because the second injection of fuel or air pressure acts as a catalyst–something that encourages or speeds along a chemical process– to the super-heated reaction of the soot particles. This reaction lets the soot be used to further power the truck.

4. What is a DPF System?

A DPF system refers to the entire system of parts, including the DPF filter itself that filters solid particles from the exhaust and uses them to power the truck. This power is added to the power that comes from the initial diesel fuel burn.

5. What’s the Difference Between DPF and EGR (Exhaust Gas Recirculation)?

A DPF filter is sometimes part of a Selective Catalytic Reduction (SCR) system. SCR systems and EGR systems are two different ways of solving the same problem.

i. Exhaust Gas Recirculation

An EGR system is an Exhaust Gas Recirculation system. Both EGR and SCR systems are ways of reducing harmful carbon emissions and air pollution from exhaust. They’re also both systems designed to make diesel fuel last longer so the driver doesn’t have to refuel so frequently.

While there are pros and cons to both types of systems, EGR systems that incorporate a DPF filter are more popular and often considered superior to SCR systems in the truck industry. However, SCR systems may also incorporate a DPF filter, and this makes them more effective at reducing air pollution.

The basic difference is, EGR systems do not produce as much toxic exhaust (NOx) because the exhaust is repeatedly recycled, whereas SCR systems do create NOx, but then they destroy it, breaking it apart with an injection of a chemical compound that reacts with the NOx to create water vapor.

ii. Fuel-efficiency

SCR systems are more fuel-efficient than EGR systems if the SCR system uses a DPF filter.

EGR systems recycle exhaust by recirculated exhaust gas back into the cylinders. To do this safely, the gas has to be cooled and mixed with fresh air. The gas cooling components of an EGR system can make them less fuel-efficient because running the cooling systems uses up some of the energy.

However, if the EGR system uses a DPF filter, then the passive regeneration of the particles while on the highway can make up for the inefficiency that stems from the cooling system being activated during active regeneration.

Active DPF
Source: Flicker

SCR systems use diesel emission fluid (DEF), which “causes a chemical reaction that allows the exhaust molecules to meet the emission requirements,” according to Patrick Webb, the sales director of GE Transportation. DEF is useful, but it’s another element to keep track of, something to purchase, store, and maintain.

Ultimately, SCR and EGR systems are both useful ways to increase fuel efficiency and reduce carbon emissions. Either one might incorporate a DPF filter.

Make sure that, whichever system you choose; the specific design meets the current EPA regulations for diesel engines.

6. Is DPF Mandatory? Is Removing a DPF illegal?

Replace DPF Filters

Removing a DPF filter without replacing it is illegal.

The informative website Do Not DPF Delete explains the law in plain terms:

According to Section 203 of The Clean Air Act, it is illegal to tamper with, remove or be involved in the deletion knowingly or unknowingly of the DPF system of a truck. What this means is that you may face penalties under the law will for not only the removal but also the physical alteration of the DPF.  Furthermore, it is also illegal to use a DPF removal service provider to do this for you.

They also point out the heavy fines someone might incur from unlawfully removing a filter: “a carrier in California was hit with a $400,000 fine due to DPF violations.

While it isn’t mandatory to use a DPF filter specifically, it is mandatory to meet EPA regulations when it comes to reducing carbon emissions and other forms of air pollution caused by diesel exhaust. If a diesel engine has a DPF filter installed, then that’s the tool the engine is using to reduce air pollution and meet EPA standards. Without it, the engine won’t pass the test, and harmful fumes will be released by the exhaust.

Fortunately, if a DPF filter is causing problems, it’s likely that it still doesn’t need to be replaced. Instead, it probably just needs to be cleaned.

7. How Often does a DPF Filter Need to be Cleaned?

On average, a DPF filter needs to be cleaned every 200,000 kilometers, or around 124,000 miles. However, any specific filter may get clogged or blocked sooner than that, especially if the truck is on the highway less often than average, and spends more time running at lower speeds.

The main sign that your DPF filter is clogged is the orange warning light on your dashboard will turn on. Other signs are:

  • passive and active regeneration failure
  • a persistent intense diesel smell
  • an increase in the truck’s fuel consumption
  • an excessive amount of smoke being released through the exhaust pipe

Check the DPF filter if you experience any of these warning signs.

8. Why is the DPF Blocked? What is Preventing DPF Regeneration?

The number one reason a DPF filter gets blocked is it doesn’t experience enough passive regeneration, which burns off the soot that the filter traps and uses it for fuel. Passive regeneration can only happen at high speeds, such as on the freeway. If the truck hasn’t been driven at high speeds frequently enough, the engine won’t have enough opportunities to burn off the soot.

That said, eventually, the DPF filter will get blocked even when the truck is being used normally. DPF regeneration is prevented if there are so much soot and particulates clumped in the filter that it won’t completely burn off, even at high temperatures. This happens when the filter hits 85% soot capacity or higher. When that happens, the gaseous exhaust can’t pass through. Rather than a wall with holes, the DPF filter just becomes a wall. Continuing to use the filter without cleaning it in this state can permanently damage the filter.

It’s important to clean the filter at this point or, if it’s damaged, to replace it.

9. Which DPF Cleaner is Best?

There are three categories of DPF filter cleaners.

A. Liquid DPF Filters Cleaner

Liquid DPF cleaner is a chemical compound added to fuel that mixes with soot particles, changing them into a new compound. This new compound burns at a much lower temperature. The truck can burn off more of the soot through passive and active regeneration, even if there’s a lot of it.

By changing the soot into a new compound, the cleaner makes it easier for the heat of the internal combustion to burn the compound and strip the filter through the regular regeneration process, letting exhaust pass through the filter once again.

Cleaners differ on their environmental friendliness, their precise chemical makeup, how affordable they are, and how much fuel it can work with. Doesn’t Delete DPF explore the pros and cons of three popular liquid DPF cleaners in 2019?

B. Mechanical DPF Filters Cleaner

There are mechanical DPF filter cleaning options to take advantage of if regeneration isn’t working, even with cleaning fluid applied. Typically, that means ash has built up in the filter, which can’t be burned during regeneration. These are sometimes called high-pressure cleaning cabinets.

Mechanical DPF filter cleaners use methods including compressed air, ash containment, and pre-programmed cycles to target ash and heat, blast, or cut it away from the filter.

In a useful whitepaper, the Automotive Parts Remanufacturers Association analyzed the costs and benefits of these mechanical DPF filter cleaners and concluded that they’re very cost-effective, especially compared to replacing a damaged filter.

Typically, these mechanical DPF cleaners are owned by mechanic shops rather than individual truckers.

C. Manual DPF Filters Cleaning

Cleaning a DPF filter by hand is tricky, and typically requires specialized training. That said, a person can learn anything on YouTube nowadays. The YouTuber Big Rig Fix demonstrates how to remove the DPF filter from a Freightliner Cascadia truck to clean it.

Then, the YouTuber Guddu Pappu has a how-to video demonstrating how to clean a DPF filter using soap, buckets, and water pressure. It’s a delicate process, but one you can learn if you’re determined–and aren’t afraid of the risk you might damage your DPF filter on your first try.

10. How to Replace the DPF Filter?

Sometimes a DPF filter cannot be saved by cleaning; the ash buildup, overuse, or an accident of some kind has damaged it beyond repair. If someone attempts to clean a DPF filter but the orange warning light remains on, or if a mechanic advises a driver that the filter is damaged, it’s time to replace it.

At Mytee, we have a wide selection of replacement DPF filters. Our DPFs are brand new, not refurbished or recycled. Even though they’re new and manufactured in the United States, each DPF filter is affordably priced because we sell directly to you– no money wasted on a middleman. The EPA has an excellent, free guide to installing your new, replacement DPF filter.

Also, the California Clean Air and Water Resources Board produced a video on DPF filter replacement, demonstrating each step of DPF filter installation.

11. Who Buys DPF Filters and Systems?

It can be disheartening to have to toss out an expensive piece of equipment like a DPF filter, even if it no longer works. Fortunately, some businesses will buy dysfunctional and damaged DPF filters for the materials. Ceramic, cordite, and silicon carbide are in high demand as raw materials. So discarding a filter doesn’t have to be a total loss. It’s very possible to sell a damaged filter and put the money towards a new one.

DPF Filters

The most popular, legitimate places to sell used and damaged DPF filters are:

  • DPF Recovery
  • Scrap DPF Buyer
  • DPF Recycler

12. Does DPF Work with Biodiesel or Other Alternative Fuels?

DPF filters are a tool to make exhaust cleaner and to do our part to pollute the airless.

Many environmentally-conscious drivers want to do more for the environment, so they’re interested in biodiesel and alternative fuels. The short answer is YES. According to the United States Department of Energy, “all diesel vehicles can operate using biodiesel.”

Plus, a study published in the scientific paper Effects of biodiesel on continuous regeneration. DPF characteristics found that “Test results show that at the same engine operation conditions the fuel consumption is higher for biodiesel. DPF has better filtration efficiency for biodiesel PM, and the use of biodiesel to engine assembled with DPF has significant benefits.”

This means, not only do DPF filters work well with biodiesel. They are even more effective with biodiesel than with regular diesel. That said, outside of biodiesel, the category of “alternative fuels” is broad. It’s important to research the specific fuel you want to use to see if it’s compatible with a DPF filter.

Whew! That was a lot to unpack! Thirteen key DPF questions were answered, all in one place.

Have even more questions about DPF filters? Or, do you want to schedule a consultation and installation, or simply want to order one for yourself?

Call the experts at Mytee Products: 1-888-705-8277

Email us at  [email protected], or catch us on YouTube, Facebook, Twitter, or Pinterest.

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