Posted on 11/28/2025
If you drive a modern diesel, the diesel particulate filter (DPF) is the reason your exhaust stays clean. It traps soot during normal driving, then burns that soot into ash during a process called regeneration. Regeneration is built into the car’s software, and when it works as intended, you barely notice it. Problems start when regens are interrupted or the car never gets the right conditions to complete them. What the DPF Catches and Why It Needs Regeneration A DPF is a ceramic honeycomb that traps microscopic soot. Over time the cells fill up and backpressure rises. To clear it, the engine raises exhaust temperature so the soot burns into a small amount of ash. Ash stays in the filter and accumulates slowly with mileage, which is why very high mileage diesels eventually need a professional cleaning or replacement even if nothing is broken. Three Types of Regeneration There are a few ways the system cleans itself: Passive regeneration hap ... read more