Hillend: Petrol in a Diesel Car? How Worried to Be
Unstarted? Then less worried than you likely feel. Everyone around Hillend begins with "have I ruined it?", and the honest answer is generally no: petrol left inside that tank of a diesel stays harmless till priming, cranking or driving draws it into the fuel system. Petrol in Diesel is who to phone, with the motor kept off, and so it remains that way. Further down, you will find what petrol actually does inside a diesel, how far it might have got, and how to stop it happening to you again.
The engine and petrol in a diesel: what goes on
Diesel has two jobs on its way through an engine. Before it burns, it protects — and then it combusts. What stops the surfaces inside the high-pressure pump and the injectors from wearing down against each other is the diesel flowing through them — they're built to extremely fine gaps.
The second task petrol doesn't do at all, and the first it does poorly. The rattling comes from petrol being made not to ignite when compressed, which is exactly the opposite of what a diesel needs. On top of that it is runnier than diesel, it strips away the lubrication the fuel system hinges on, and any pump working on that blend is wearing itself.
Taken together, they show the shape the trouble has. It's circulation that does the damage, not contact. Where the petrol is only in your tank, it's a problem of fuel, nothing more. Once the pump has been working on that petrol, a mechanical fault has started: anything shed by a pump that's grinding travels onward to your injectors with the fuel.
Hillend, petrol in a diesel: four situations, from mild to serious
The best case there is: filled up, not once started. Being at a forecourt is what makes this possible: elsewhere, the car has been driven there to begin with. With that petrol held inside your tank alone, it is emptied and rinsed on the spot, and nothing more is needed.
Started for a second, or only your ignition on. Petrol has come out of that tank and got to the fuel filter and the fuel lines, because the fuel system has been bled. That's generally still a simple task — a drain, a flush, and your filter seen to.
Those few miles driven were your pump running on fuel weakened by petrol throughout. Distance is only half of it; how hard it was driven matters equally. Either way the work includes that tank, your lines, the fuel filter and clean fuel through the whole system. Driving the kids to the local primary school is one kind of trip. Very different again: a trip to Dunfermline, under 5 miles away, or some distance on the M90, under a mile from Hillend, where the motor never stopped labouring hard.
Knocking, an uneven idle, smoke, a throttle gone soft: driven till it complained. The motor is telling you your fuel is no longer acting like diesel. Stop on the spot — on the verge on B916, at the kerb, down a side road — and do not move it again. Long-term damage is very unusual if a vehicle is stopped early, and the drain and flush-through that still go first sort it out.
Stories Hillend drivers hear about petrol in a diesel
"Top it up the rest of the way with diesel and it will be fine" — a myth. It won't. Nothing is removed by topping up — you're left with a fuller tank, still the same mixture. The assumption behind the advice — that diesel fuel systems tolerate petrol by percentage — is wrong.
"Modern diesels can handle a little petrol" — a myth, and closer to the reverse. Lubrication matters more on modern diesels, not less, because their fuel passes through more precise parts at higher pressure.
One myth that catches people off guard: if it starts and drives, it must be unharmed. Diesel in a petrol motor usually leaves a motor that will not run: the driver stops, and so does the damage. Nothing seems to have happened when a diesel fed petrol fires up, ticks over and drives away, which it usually will; meanwhile the pump wears. Running isn't the same as fine.
Myth: "Add some two-stroke oil and drive the car home." It is an old workaround for a separate problem. The petrol is still inside your tank afterwards, and whatever it has weakened is not put back.
The next start sends petrol back round your pump out of the lines and the fuel filter, where some of it ends up once the motor has run. That's why a DIY tank drain does not sort it — a myth. It is also truly risky to drain petrol into a can by the kerbside.
Why petrol in a diesel takes place so easily
On purpose? Never. Through carelessness? Rarely, if ever. One way only, since of the nozzles: the narrower petrol one slips inside a diesel filler with almost no resistance, while the diesel one mostly won't fit a petrol motor. That is how the forecourt makes it simple.
The moment routine stops matching your car is the moment it occurs. A new vehicle, a hire car or a courtesy car. Households running one of each, petrol and diesel. The pumps in a different order on a well-known forecourt. A train to catch, and a rushed fill on the way to Dalgety Bay. Exactly the moment it takes place: after years of driving petrol, a driver fills a diesel Volkswagen Golf for the first time. Add rain, a phone call or a back seat full of kids, and your hand does what it has always done.
Preventing petrol in a diesel next time you fill up in Hillend
- The label is what matters, and so check the petrol pump instead of the colour: in the UK unleaded handles are normally green and diesel black, yet not on every forecourt.
- Plenty of motors state the fuel type inside your filler flap or on the cap, and so check there on your first fill in a car you don't know.
- A coloured fob or a sticker on your diesel's key achieves more than any amount of meaning to remember, in a house with one of each.
- It seems silly and it does the trick: on the first fill in a new or hired car, say "diesel" aloud before you take the nozzle off the pump.
- While you're thinking about something else, this is an easy mistake to make — so tuck the phone away.
- Up to a point, a misfuel inhibitor helps: some diesels come with a filler designed to block a petrol nozzle, and add-on devices exist for the rest. Treat it as a backstop, and keep reading the pump.
- Noticing it halfway? Stop at once. A weaker mix follows from less petrol in that tank, but your next stage stays the same: do not start it.
Hillend: already put petrol in a diesel?
Then, there is only a short order of things. Don't fire it up, and don't turn your ignition on. Yet on the forecourt, at BP or anywhere else? Ask the staff to help you roll the car away from the pump. Next, 0333 366 0103. We will ask what went in, roughly how much, and if it has been run.
Corrosion and deposits form the trouble with AdBlue, whereas petrol means lost lubrication. So if it was AdBlue, say so — and see its own Hillend page.
What makes one Hillend petrol in a diesel task cost more than the next
The four situations above are four separate tasks, so no single price for this would be fair. The situation itself does most of the work of moving your cost. Two things follow that: the petrol that got in as a proportion of what your tank holds, then the place the vehicle is in and whether a technician can get to it safely.
That is why our technicians ask three queries before quoting instead of after: what was put in, how much, and whether it's run. The replies turn a range into a straight figure.
About Hillend itself
Hillend is a small coastal village in Fife, situated near the town of Dunfermline and overlooking the Firth of Forth. Hillend has a population of around 581 people and is characterised by detached housing. Hillend sits at an elevation of 33 metres, close to nearby places such as Dalgety Bay and Fordell Firs.
Across Fife and around Hillend: fuel drain cover
Hillend rests in the KY postcode area, and the vans that answer petrol in diesel jobs there work the locations around it as well — Dalgety Bay, Fordell Firs and Duloch among them. The vehicle doesn't need to come to us: our engineers drain on a forecourt, in a supermarket car park, in a lay-by or on your own driveway.
In Hillend and still at the petrol pump?
The best spot there is, then — that is where you are. Keep it off. Call.