There are two ways that DPFs get choked. The first is by soot, primarily from too many short runs from cold starts especially in winter and for a new car that can be in as little as 1,000 miles. The second is by ash in a well used diesel vehicle where the ash can take 65,000 - 120,000 miles to block the DPF after which it may be possible to clean it out using the Ceramex process, or the vehicle may need a new OEM DPF.