A diesel particulate filter (DPF) is a component of the exhaust system that captures diesel particulate matter (soot). When the filter is full, the engine goes through a cycle known as active regeneration. During the active regeneration cycle, the engine's idle speed is increased and diesel fuel is injected into the exhaust stream to raise temperatures in the DPF, effectively burning off soot captured in the filter. While the use of a DPF is highly effective in eliminating up to 99% of diesel soot emissions, the DPF is a very restrictive device, and the active regeneration cycle significantly damages fuel economy. DPFs are currently found on all new Duramax, Cummins, & Power Stroke diesels in order to comply with strict EPA mandated diesel emissions regulations.

Deleting the DPF is legal for offroad use only. As outlined by the U.S. Clean Air Act, tampering with any emissions control device on a vehicle is illegal. Deleting the DPF is a punishable offense, although it is not yet widely enforced by the EPA. For this reason, most manufacturers and installers of DPF delete kits require purchasers to sign an "offroad use only" waiver, limiting or eliminating their liability. In States that require emissions inspections and/or testing for diesel pickups, DPF removal will immediately result in a failed inspection.

With that said, your frustrations with the DPF system are understandable and has resulted in several lawsuits targeting lawmakers at the Federal and State level. When particulate filter systems were first introduced, fuel economy and reliability gravely suffered. Technology has since advanced and many of the concerns have been addressed, but this does not mean that the DPF is without serious disadvantages.


  • Reduced fuel economy - Active regeneration cycles introduce raw diesel fuel into the exhaust stream in order to raise the temperature of the DPF, burning off particulate matter trapped in the filter and effectively cleaning it. This results in significantly reduced fuel efficiency, obviously stemming from the use of fuel for means other than propulsion.
  • Excessive cylinder washing & fuel dilution - Certain model year trucks suffer from excessive fuel dilution and cylinder washing as a result of the active regeneration process. These trucks inject fuel into the combustion chamber late in the exhaust stroke so that the unburnt fuel travels into the exhaust stream. This contributes to fuel dilution of the engine oil and cylinder washing, which removes the thin film of protective engine oil from the cylinder wall. The industry has since moved towards the use of a dedicated injector which injects fuel directly into the exhaust system, eliminating concerns.
  • Reduced reliability, increased downtime - Serious reliability concerns have arose regarding aftertreatment systems, the most common of which is filter clogging. Under ideal conditions, the DPF should not clog and regeneration cycles should be automatically initiated as necessary to periodically clean the filter. However, filter clogging has become an ongoing problem for many owners and the reliability of the systems has come into question on many occasions.
  • Safety concerns - The temperature of the exhaust system can exceed 1000° F during active regeneration, increasing the risk of fire. DPF equipped trucks should not be operated in/around tall grass or other environments where there is a high risk of starting a fire. There have also been instances of trucks catching fire, the causes of which are believed to have been a malfunction of the DPF system. This is one of several concerns being cited in lawsuits against the California Air Resources Board (CARB), whom has required the retrofitting of semis operating within CA with DPF systems.

In full disclosure, it's worth noting that the introduction of selective catalytic reduction (SCR) and the use of diesel exhaust fluid (DEF) has greatly improved the fuel economy and reliability of emissions controlled diesels by significantly reducing regeneration cycle frequency.


The concept of a DPF delete is simple; replace the factory aftertreatment system with straight exhaust tubing and disable the regeneration system with programming. In practice it's not quite as simple as installing a section of exhaust tubing, as the PCM must be reprogrammed to disable the regeneration system. Without purchasing and installing a complete kit, various trouble codes will be triggered and the engine may not operate properly. Some DPF delete manufacturers claim up to a 7 mpg increase in fuel economy. Actual results will vary considerably depending on driving conditions.

Considerations Before Deleting the DPF

  • Diesel soot is a known cancer causing agent. The government bodies whom have fought to reduce emissions on diesel vehicles have done so with good intentions, albeit with questionable execution. The link between cancer and particulate matter produced by the combustion of diesel fuel is not a myth, it's well documented science resulting from years of study. Note - we are in no way, shape, or form protecting, creating excuses for, or justifying the actions of the EPA or CARB.
  • The performance aftermarket is currently unregulated (for the most part). However, continued abuse is likely to strip the industry of many freedoms. The "Rollin coal" epidemic, for example, has caused many diesel performance manufacturers to pull certain race oriented products.
  • More States are likely to follow California's lead. California has some of the strictest emissions regulations on diesel powered vehicles. This includes a mandatory inspection once every 2 years. As tampering with emissions equipment becomes more widespread, lawmakers are likely to enact stricter regulations and more severe penalties, following the direction of the CARB.