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Diesel in a petrol car
A diesel nozzle is wider than most petrol filler necks, so this one is rarer — but it still happens, especially with older cars, vans and wide-neck fillers.
Do this now
- 1Don't start the engineDon't turn the ignition on either. Keyless? Keep the fob away from the car.
- 2Neutral and push clearAsk staff to help push the car away from the pump.
- 3Tell the cashierThey deal with misfuels every week.
- 4Call Mr FuelFixed price and arrival time on the phone.
On a motorway? Get behind the barrier first. In danger, call 999.
Diesel is thick and oily and won't ignite from a spark. If you run the engine it will misfire, smoke heavily and stall, coating spark plugs and sending unburnt fuel towards the catalytic converter. The good news: drained before the engine runs, there's usually no lasting harm.
Signs you need us
- Heavy white or grey smoke from the exhaust
- Misfiring, spluttering or stalling soon after filling up
- The engine won't start, or starts and cuts out
- A strong smell of diesel
How we fix it
- 1Make safeCar stays where it is, in neutral if it needs pushing clear of the pump.
- 2DrainThe full tank is drained through a sealed pump into an approved container.
- 3FlushTank and lines are flushed with fresh petrol. If the engine ran, we check plugs and advise on anything we find.
- 4Refuel and testWe add fresh unleaded, start up and confirm the car runs smoothly.
- 5Dispose legallyWaste fuel leaves with us under a waste transfer note.
Good to know
- Running on diesel can foul spark plugs and damage the catalytic converter.
- Unburnt fuel can contaminate the engine oil on some engines.
FAQs
Diesel in a petrol car: questions
Is diesel in a petrol car as bad as petrol in a diesel?+
Usually less damaging, because the engine simply refuses to run well rather than wearing its fuel pump. But it still needs draining — a petrol engine will not clear diesel by itself.
Can I top up with petrol to dilute it?+
No. Diluting doesn't change what's in the tank, and any diesel that reaches the engine will cause misfires. Drain it.
My hybrid has diesel in it — can you help?+
Yes. Petrol hybrids are drained the same way. We take care not to let the car start its engine automatically while we work.
Related
Other problems we fix
Diesel in petrol help near you
Wrong fuel? Don't start the engine.
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