Diesel Particulate Filter (DPF) Damage from Misfuelling: What You Need to Know
Modern diesel vehicles rely on a Diesel Particulate Filter that is easily damaged by petrol contamination. Here is what DPF damage looks like after a misfuel and what it costs to fix.
What Is a DPF and Why Is It Vulnerable?
The Diesel Particulate Filter is a ceramic substrate fitted in the exhaust system of modern diesel vehicles to trap soot and particulate matter. It operates at extremely high temperatures during "regeneration" cycles, burning off accumulated soot. A DPF is designed to operate with diesel combustion characteristics — temperature profiles, exhaust chemistry, and regeneration cycles calibrated for diesel fuel.
How Petrol Contamination Damages the DPF
When petrol combustion occurs in a diesel engine — even briefly — exhaust temperatures and chemistry change significantly. Unburnt petrol vapour in the exhaust system can cause abnormal DPF temperatures during a forced regeneration, cracking the ceramic substrate. Additionally, the wash effect of petrol through the cylinders can deposit excessive soot and unburnt hydrocarbons in the DPF in a short time, blocking it beyond the point where regeneration is possible.
DPF Replacement Costs in New Zealand
DPF replacement is one of the most expensive outcomes of a misfuel in New Zealand. A new DPF for a popular diesel SUV — Toyota Fortuner, Ford Ranger, Mitsubishi Pajero Sport — ranges from $1,500 to $4,500 for the part alone, plus labour. This is in addition to the fuel system flush, filter replacement, and potential injector work. DPF damage is one of the primary reasons fast response to a misfuel is financially critical.
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