Many drivers know the feeling when your truck repeatedly triggers a “regen” (regeneration), sometimes more often than seems reasonable. When regen cycles become frequent, prolonged, or never seem to end, that is a major concern. Your Diesel Particulate Filter (DPF) may be filling with soot faster than it can burn it off or failing to complete the cleaning cycle.
Frequent regens can signal upstream mechanical issues, poor driving habits, or improper maintenance, and over time, lead to reduced fuel economy, derates, or even costly aftertreatment system damage.
This edition of our Maintenance Monthly breaks down some common causes of regens, proper DPF maintenance intervals, and when to seek professional help.
Often, frequent truck regening is a symptom of underlying engine or exhaust system issues. These are some of the most common:
If your engine is burning oil or coolant, contaminants enter the exhaust stream and increase soot or ash levels. This overloads the DPF and causes more frequent regen cycles.
Faulty or dirty injectors can produce an improper fuel spray pattern, leading to incomplete combustion and excess soot. This raises the soot load in the DPF and can cause repeated or prolonged regens.
Problems with turbocharger performance, restricted/leaking air intake, EGR valve issues, or clogged/leaking coolers can disrupt proper airflow. When airflow is compromised, combustion suffers and soot output rises. Poor airflow can also prevent the exhaust from reaching the temperature needed for successful regens.
Frequent idling and stop-and-go driving do not allow exhaust temperatures to rise high enough for passive regeneration. As a result, soot accumulates more quickly, requiring more active regens.
Trucks that frequently operate at low speeds, low RPMs, or with minimal loads struggle to achieve the temperatures needed for efficient soot burn-off. This forces the aftertreatment system into more active regeneration, increasing fuel consumption and wear.
While regen events can occur frequently depending on driving conditions, the DPF itself must also be cleaned or serviced at set intervals. Many factors including duty cycle, affect how often you should maintenance your DPF.
Below we have listed some of the current DPF maintenance intervals for new trucks equipped with Paccar and Cummins engines.
Current Paccar MX-13 Engine DPF Maintenance Intervals*
Duty Type | Miles | Hours |
Normal Duty/Line Haul (Less Than 20% Idle Time) | 300,000 | 6,750 |
Normal Duty/Line Haul (Greater Than 20% Idle Time) | 300,000 | 6,750 |
Severe Duty/Vocational | 150,000
| 4,500 |
Pick-up/Delivery/Refuse | 150,000
| 4,500 |
*Effective as of the date of this publication.
Current Cummins Engine DPF Maintenance Intervals*
Engine | Miles | Hours |
X15 Efficiency Series | Severe Duty: 250,000-400,000 Normal Duty: 400,000 – 600,000 Light Duty: 600,000
| – |
X15 Performance Series | Severe Duty: 250,000-400,000 Normal Duty: 400,000 – 600,000 Light Duty: 600,000
| – |
B6.7 For Medium-Duty | 200,000
| 6,500 |
L9 For Medium-Duty | 200,000
| 6,500 |
*Effective as of the date of this publication.
New truck models may require less frequent intervals, but these cleanings are still essential for long-term system health.
If your truck is regening more frequently than normal, failing to complete regen cycles, losing power, or showing high soot/back-pressure readings, it’s time for a professional inspection. In many cases, the DPF is not the root cause — upstream engine or airflow issues are.
If your truck is regening frequently, please seek assistance from professionals to ensure your truck is properly inspected and repaired. The Kenworth of Pennsylvania team can help with that. Our expert service technicians are here to help call your local Kenworth of Pennsylvania store to learn more and schedule a service appointment with us today.