The most important step is simple: do not start the engine or switch on the ignition. Circulating contaminated fuel can turn a drain-out into a larger repair.
The short answer
- Do not start the engine or switch on the ignition after misfuelling.
- Tell forecourt staff, keep the key controlled and arrange safe movement and specialist help.
- Tell the provider exactly which fuels were involved, how much was added and whether the engine ran.
At the filling station
Tell station staff and move the car only if staff say it can be pushed safely. Call a specialist drainage service and give the vehicle, correct fuel, wrong fuel, approximate amount and whether the ignition was used.
Quick checklist
- Keep the keys away from anyone who may start the car
- Do not try to dilute the tank
- Confirm call-out and drainage charges
- Prioritise personal safety and call 999 in immediate danger
If the engine has been started
Stop when it is safe, switch off and explain exactly what happened. Do not repeatedly restart the vehicle. The provider may recommend further inspection depending on the fuel and system.
After drainage
Ask what was removed, whether the system was flushed, what fuel was added and whether further checks are recommended. Keep the invoice and any diagnostic record.
Why petrol in diesel and diesel in petrol are different
The fuels have different ignition and lubrication properties. Modern diesel fuel systems use the fuel as part of their lubrication, while petrol contamination can reduce that protection. Diesel in a petrol system can cause poor running and contamination. The quantity, vehicle design and whether fuel circulated all affect the response.
Do not use a generic percentage rule from social media to decide that dilution is safe. Give the specialist and, where appropriate, the vehicle manufacturer or recovery provider the exact facts.
What to include when comparing fuel-drain quotes
Confirm call-out, drainage, flushing, replacement fuel, filters, disposal, VAT, travel distance and what happens if the vehicle has already run. Ask whether the operator carries suitable insurance and what written record or warranty is provided.
Questions drivers ask
Can I fill the rest of the tank with the correct fuel?
Do not assume dilution is safe. The correct response depends on the fuels, quantity, vehicle and whether the system has circulated them. Stop and get vehicle-specific professional advice.
What if I only switched the ignition on?
Some vehicles prime the fuel system when unlocked or when the ignition is switched on. Tell the provider exactly what happened and avoid repeating it.
Official sources and further reading
Related emergency guides
Turn the guide into a useful next step
Estimate the cost, compare relevant local providers or request written garage quotes for the same job.