Put the Wrong Fuel in Your Car?
Stop. Do Not Start the Engine.
If you have put the wrong fuel in your vehicle, the single most important thing you can do is not turn the ignition. Starting the engine circulates contaminated fuel through the system, dramatically increasing the damage and cost of repair.
Misfuelling — putting diesel in a petrol car or petrol in a diesel car — is one of the most common roadside incidents in New Zealand. It happens to thousands of drivers every year, often at busy self-service stations where distraction is high. The good news is that if handled correctly, the damage is usually minimal and your vehicle can be back on the road the same day.
What To Do — Step by Step
If you haven't turned the key or pressed the start button, leave it. If the engine is running, turn it off immediately. Do not attempt to drive to a mechanic.
Release the handbrake and have someone help you push the vehicle away from the fuel pump to a safe area of the forecourt.
Let the station attendant know what has happened. They deal with this regularly and can assist with moving the vehicle.
Contact one of the three NZIFDA-certified compliant operators to dispatch a technician. They will remove the contaminated fuel using the manufacturer-specified procedure for your vehicle.
Most comprehensive car insurance policies cover misfuelling. Your insurer may have a preferred operator — check if they work with an NZIFDA-certified provider.
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Types of Misfuelling
Diesel in a Petrol Car
Diesel fuel in a petrol engine causes spark plug fouling, injector clogging, and catalytic converter contamination. If not started, the fuel can usually be drained and flushed with minimal damage. If the engine has been run, more extensive cleaning may be required.
Read the full guide: Diesel in Petrol →Petrol in a Diesel Car — Most Dangerous
This is the more serious scenario. Diesel fuel acts as a lubricant for the high-pressure fuel pump. When petrol replaces diesel, it strips away this lubrication, causing metal-on-metal contact that can destroy the fuel pump, injectors, and fuel rail. If driven, damage can run into thousands of dollars.
Read the full guide: Petrol in Diesel →How Much Does Misfuel Recovery Cost?
Will Insurance Cover It?
Approximately 59% of vehicle insurance policies exclude misfuel repairs entirely — up from 49% in 2016. Where coverage exists (typically comprehensive policies), you will need to pay your excess, but the fuel removal and necessary repairs may be covered. However, the repair method matters:
Always check with your insurer before authorising work, and ensure the operator uses manufacturer-prescribed methods.
Will It Void My Warranty?
Every vehicle manufacturer classifies misfuelling as vehicle misuse and excludes it from warranty. GM, Toyota, Ford, Audi, BMW, Mercedes-Benz, Hyundai/Kia, and all other manufacturers take this position — misfuel damage is not a manufacturing defect. However, the repair method creates a second warranty risk: if filler neck extraction damages anti-siphon devices, rollover valves, or other filler neck components, the manufacturer has no obligation for any subsequent fuel system issue — even on components that would otherwise be covered. Using manufacturer-prescribed methods (fuel pump access or tank removal) avoids this additional risk.
Why Use an NZIFDA-Certified Operator?
NZIFDA-certified operators are the only providers in New Zealand that have been independently verified for Dangerous Goods licensing, insurance, OEM-prescribed fuel removal methods, and proper hazardous waste disposal. They use the same methods prescribed in your vehicle's manufacturer service manual — fuel pump access panel removal or full tank removal. No manufacturer anywhere in the world prescribes filler neck extraction. Using an uncertified operator who uses this method can damage safety-critical anti-siphon components, void your remaining warranty, invalidate your insurance claim, and result in incomplete fuel removal that causes ongoing damage.
Learn more about NZIFDA Certification → | View your vehicle's manufacturer procedure →
Misfuelling Prevention
The easiest way to prevent misfuelling is to pay attention at the pump. Diesel nozzles are typically larger than petrol nozzles, and most modern diesel vehicles have labels near the fuel cap. Aftermarket misfuelling prevention devices are available for both petrol and diesel vehicles.