A modern diesel DPF runs a passive regen continuously above about 40mph at steady throttle, and an active (forced) regen roughly every 200-400 miles depending on use. If you mostly do short, slow journeys, your DPF won't get hot enough to complete a regen and will eventually block — that's the £1,000+ problem you're trying to avoid.
DPF regens are misunderstood by almost everyone — including some garages. Here's how they actually work.
Can I trigger a regen myself by driving? — You can't manually start one — only the ECU does that — but a 30-minute drive at 60mph in a low-ish gear (2,500-3,000 rpm) will let any in-progress regen complete and encourages another one if soot levels are high.
What's the difference between a DPF clean and replacement? — Cleaning (ultrasonic or chemical, off the car) removes built-up ash and unburnt soot from a partially blocked DPF — £300-£600. Replacement is for a DPF that's cracked, melted or completely overloaded — £800-£2,500+ depending on car.
Why does my car smell when it regens? — Hot fuel and burning soot — totally normal during an active regen. If the smell is heavy diesel (not burning), you may have an injector dribbling extra fuel into the DPF, which is a fault.
Bob's Mechanical Repairs — independent family-run garage in Birnam, Dunkeld, Perthshire. Call 01350 727 276 or email [email protected].