Catalytic converters and DPFs are consumables only in the sense that abuse consumes them. Treated well, both can last the life of the vehicle. The habits below are what “treated well” actually means — and every one of them is cheaper than a replacement part.
Looking after your DPF
- Give it a proper run regularly. If most of your journeys are short and urban, take the car for a sustained drive — 40mph or more for 15–20 minutes — every week or two so regeneration can complete. If virtually all your driving is short urban hops, it’s worth asking honestly whether a diesel is the right car for the job at your next change.
- Never ignore the DPF warning light. When it first comes on, a sustained run following the handbook’s advice usually clears it at zero cost. Left ignored, the filter passes the point where driving can save it, then the point where a garage can save it.
- Use the correct low-ash (low-SAPS) engine oil. Ordinary oil leaves ash that permanently fills the filter — it’s the specification on the bottle, not the brand, that matters. After any service, it’s fair to ask what specification went in.
- Keep additive systems topped up. If your vehicle uses a regeneration additive (many Peugeot, Citroën and Ford models), never run it empty — regeneration silently stops without it.
- Fix engine-management lights promptly. Almost any active fault stops regeneration from initiating, so an unrelated-looking sensor fault can quietly block your DPF while you put off the garage visit.
- Be wary of biodiesel blends beyond what the manufacturer approves — high biodiesel content is a known contributor to DPF problems.
- Don’t regularly run on fumes. Many vehicles won’t regenerate with a low fuel level (typically under about a quarter of a tank or when the low-fuel light is on).
Looking after your catalytic converter
- Keep the engine in tune. A misfiring engine sends unburned fuel into the cat, overheating and melting the core — the number one cat killer. Investigate warning lights and rough running promptly, and service to the manufacturer’s schedule.
- Never bump- or tow-start the car. Both dump raw fuel into the exhaust, which ignites in the hot cat.
- Take speed bumps and rough ground slowly. The ceramic core cracks when the underside is grounded — and a cracked core rattles, breaks up and stops converting.
- Mind deep water and snow. A working cat runs at several hundred degrees; hitting deep puddles, fords or snowbanks chills the steel shell far faster than the ceramic inside, and in extreme cases the contracting shell crushes the core.
- Use fuel additives only if confirmed cat-safe. If the label doesn’t say it’s safe for catalyst-equipped vehicles, don’t use it.
- Don’t tow beyond the car’s limits. An overloaded outfit pushing the car downhill sends unburned fuel into the exhaust with the same melting effect as a misfire.
- Don’t park over long dry grass. An exhaust at operating temperature genuinely can set it alight.
If prevention has come too late, start with the diagnosis guides — why cats fail and why DPFs block — then find the right replacement with the part finder.