Understanding the Basics of your Diesel’s DPF System

DPF Filter cut-a-way
September 13, 2020

If you drive a truck made anytime over the last decade (2007 and later) you have a Diesel Particulate Filter (DPF) system on your truck to meet emissions standards. The system catches the remaining particles after the combustion cycle of your engine, similar to a catalytic converter on gas engines.

Most of the time you do not even know the system is working. Over time the filter of the system needs to be cleaned from the un-burnt components of diesel fuel, carbon and particulates that accumulate into visible smoke from the exhaust. Cleaning happens via four methods – passive, active, parked and forced regeneration cycles.

What if you could cut down on the amount of regeneration cleaning cycles (regens)? You can by using Hot Shot’s Secret Diesel Extreme and Everyday Diesel Treatment. Third-party testing by the City of Columbus cut the number of regens down by 50%!


We know regens happen because of soot build-up in the diesel particulate filter. So, if we can lower our soot output, we can lower our regens significantly. The best way to accomplish this is by achieving a more efficient burn of our diesel fuel.

There are two things needed to make this happen:
1. Having clean fuel injectors
2. Burning higher cetane rated fuel

If we keep our fuel injectors clean, we’ll get closer to the perfect mixture of fuel and oxygen in our combustion chambers. Coupling a perfect air-fuel ratio with a higher combustible fuel (more cetane), we will achieve a more efficient burn of fuel. This means less soot being pushed through our DPFs and less regens.

Regeneration Cleaning Cycle Types

Passive regeneration occurs naturally under steady driving, when the engine achieves the required operating temperature. Under normal highway driving, passive regeneration takes place as the catalyst in the DPF heats up enough to oxidize the soot and turn it into CO2. The CO2 exits through the exhaust stack while any residues left behind are converted into harmless ash that collects in the DPF canister. The process is continual, so whenever the vehicle reaches operating temperature – under steady high engine loads, the DPF will begin passive regeneration
Over time, passive regeneration is not enough to prevent soot from building up in the DPF and that’s when the second stage of cleaning is used an Active Regeneration. The truck engine computer indicates that the DPF needs cleaning, and if the operating temperature is high enough, it automatically initiates an active regeneration. In general, active regeneration begins when a small amount of fuel is introduced into the exhaust stream between the turbocharger and the DPF. This fuel is atomized into an extremely fine spray that does not burn. Instead, when it makes contact with the catalyst on the DPF, it generates intense heat -upwards of 1100 degrees Fahrenheit –that oxidizes any remaining soot on the ceramic filter. Unfortunately, this may take place once a day, depending on the type of driving and can last 30 minutes or more. During this time a lack of power may be noticed by the driver.

If an automatic regen had started but was interrupted when the vehicle was stopped and cleaning needs to be continued the vehicle information system will call for the driver to perform a manual or “parked” regeneration. Parked regens are active regenerations initiated by the driver when the vehicle is stopped and engine running. Usually there is a dash switch for initiating a parked regen.

A forced regeneration is done by a mechanic using specialized control software. This is the final step before a costly replacement of the filter is required. Filters are designed to last well over 100,000 miles and will eventually need to be replaced. Using the proper fuel and oil goes a long way in maintaining the life of the DPF system.

To further extend the life of your filter and cut down on the regen cycles use products like Diesel Extreme and Everyday Diesel Treatment. Both work to improve cetane, giving you a more complete burn of diesel and work to keep your injectors clean.