DPF
The Diesel Particulate Filter traps soot from a diesel’s exhaust and periodically burns it off at high temperature — a process called regeneration that needs sustained driving. Cars used only for short town trips never get hot enough, so the filter clogs: warning lights, limp mode and a replacement bill that can exceed £1,000. If your driving is mostly short hops, buy petrol or hybrid instead.
Example
A diesel doing only 3-mile school runs is a DPF disaster waiting to happen; the same car on motorways will never trouble it.