What Diesel particulate filter (DPF) means for you
A blocked diesel particulate filter can trigger a warning light, cost power and need an expensive replacement. Cars that mostly do short trips may never clean the filter fully, so ask the seller how the car is driven. Ask for service records and any professional filter clean.
On a test drive, check the warning light and listen for hesitation or lost power. If the car shows these signs, get a pre-purchase inspection before you pay, and treat any quick fix that only clears the light with suspicion.