Misfuelling happens roughly every three minutes in the UK. Whether it costs you a couple of hundred pounds or a couple of thousand comes down to one single decision.
Putting petrol in a diesel car, or diesel in a petrol, is one of the most common and most avoidable expenses in motoring. It happens to careful, experienced drivers constantly — usually when they are tired, in a hurry, or driving an unfamiliar car.
The one thing that matters
Do not start the engine. Do not put the key in the ignition. Do not press the start button "just to check the fuel gauge". On many modern cars, switching on the ignition runs the fuel pump.
If the wrong fuel is sitting in the tank and nowhere else, the fix is a straightforward drain, flush and refill. If it has been pumped through the fuel system, you are potentially looking at replacement injectors, a fuel pump and a full system clean — a bill that runs into thousands on a modern common-rail diesel.
Why petrol in a diesel is the worse mistake
Diesel lubricates the high-pressure fuel pump and the injectors. Petrol is a solvent, so it strips that lubrication away, and precision metal components running at enormous pressure begin wearing against each other almost immediately. That is why the damage escalates so fast once the engine is running.
Diesel in a petrol engine is generally less destructive — the car will usually refuse to run properly, misfire and produce white smoke — but it still needs draining. It is also the rarer mistake, because the petrol nozzle is narrower than the diesel filler neck.
What to do, in order
- Stop fuelling the second you realise.
- Do not start the engine or switch on the ignition.
- If it is safe, push the car to a parking bay clear of the pumps and tell the forecourt staff.
- Call us on 07961 100260 and tell us the make, model, fuel type and roughly how much went in.
- Keep your receipt. It proves what went in and when, which some insurers ask for.
If you have already driven off
Pull over as soon as it is safe. The car will probably be running roughly, losing power or cutting out. Switch it off and leave it off. Trying to "get it home" is what turns a manageable job into an engine rebuild.
Is it covered by insurance?
Some comprehensive policies cover misfuelling, though often as an optional extra rather than as standard. Check your documents before assuming either way, and where it is covered, ring the insurer before authorising any repair — they usually require an approved specialist.
Avoiding it next time
Fuel cap reminder stickers are deeply unfashionable and they work. A diesel-only nozzle guard costs very little. And if you have just changed cars — particularly if you have switched fuel type — make a deliberate point of reading the pump handle every time for the first month.
We carry out roadside fuel drains right across London and north Kent, every day of the year. Call 07961 100260 — and leave the engine off.
