Should You Worry? Petrol in a Diesel Car in Pabo
Probably less than you already are — as long as no one has started it. Everyone in Pabo begins with "have I wrecked it?", and the fair answer is usually no: petrol resting inside that tank of a diesel stays harmless till priming, cranking or driving pulls it into your fuel system. To keep the vehicle like that, phone Petrol in Diesel and leave your motor switched off. The remainder of this page explains what petrol actually does to a diesel, how to judge how far it has got, and how to make sure it does not happen to you a second time.
Petrol in a diesel: what does it do to your engine?
Two jobs fall to diesel on its route round a motor. Lubricating comes before burning; it does both. Very fine gaps are built into your injectors and the high-pressure pump, and just your diesel running through keeps those surfaces from grinding together.
Of these two tasks, petrol manages the first poorly and the second never. Being less viscous than diesel, petrol strips out the protection a fuel system needs, so a pump on that mixture wearing itself. It's equally made to resist igniting under compression — the opposite of what a diesel needs — which is why you hear the clattering.
Put those together and the shape of the trouble is clear. The damage is done by movement, not by contact. All a tank with petrol in it amounts to is a fuel problem. Whatever a worn pump sheds goes on, borne by the fuel, into the injectors downstream, which is why a pump that has been working on that petrol is where a mechanical fault begins.
Petrol in a diesel around Pabo: how serious is it? Four cases
The best case there is: filled up, not once started. On a forecourt, and truly only there, the petrol is still limited to that tank — because anywhere else your car was driven to reach it. The task is emptying and purging on the spot.
The ignition turned on, or a brief start. Petrol has left that tank and reached your filter and the lines, because the fuel system has been bled. Still generally straightforward: drain, flush, and the filter seen to.
A few miles driven, and your pump has spent every one of them labouring on diluted fuel. Distance is only half of it; how hard it was driven counts equally. Either way this work runs to the tank, your lines, the fuel filter and fresh fuel through the entire system. On the school run to the local primary school, the miles is short. Driving as far as Bangor, under 15 miles away, makes a very different task — as does any distance on the Moreton Spur, under 50 miles from Pabo, with the motor working hard the whole time.
Clattering, a lumpy idle, smoke, a throttle gone soft: driven until it complained. That is the engine telling you its fuel no longer is acting like diesel. Stop where you are — on the verge on Dalar Aur, at the kerb, down a side road — and do not move it. What comes first is still the fuel drain and flush-through, and that deals with it, with long-term damage very rare if a car is pulled over soon.
What Pabo people get told about petrol in a diesel — and the stories in it
It will not be fine. The myth: "Fill it the rest of the way with diesel and it'll be." Nothing comes out when you top up — that tank just holds more of the same blend. The idea behind the guidance — that diesel fuel systems accept petrol by percentage — is wrong.
Myth: "A newer diesel can cope with a bit of petrol." If anything, the reverse. A current diesel sends its fuel through smaller components at higher pressure, which makes the lubrication count more, not less.
Myth: "If it starts and drives, there is no harm done." This is the one that catches people. Diesel in a petrol motor usually means a motor that will not run: the driver stops, and so does the harm. A diesel fed petrol generally starts, ticks over and drives away as if nothing has happened, while the pump grinds. Running is not the same as fine.
An old workaround for a different problem is behind this one. Myth: "Add some two-stroke oil and drive it home." That petrol is still inside the tank afterwards, and whatever it has diluted isn't put back.
Myth: "Drain that tank yourself and you are sorted." Once the motor has been run, some of that petrol is no longer in the tank: it is in your filter and the lines, and it goes right back through your pump at the next start. On top of that, petrol emptied into a can by the road is truly risky.
Why petrol in a diesel occurs so easily
Nobody does it on purpose, and it's seldom carelessness. The forecourt makes it easy: the petrol nozzle is the slimmer of the two, and it slides into a diesel filler with almost no resistance, while a diesel nozzle generally won't go into a petrol vehicle at all. So the mistake runs one way.
When habit and the vehicle stop matching, it occurs. Hire cars, courtesy cars, and motors that are new to you. Households running one of each, petrol and diesel. A well-known forecourt with the pumps in a different order. A train to catch, and a rushed fill on the way to Llandudno Junction. A new-to-you diesel Volkswagen Golf, its first fuelling, and a motorist accustomed to petrol: precisely when it occurs. With rain, a call coming in, or a car full of children to deal with, the hand simply does what it has always done.
How to prevent petrol in a diesel on your next fill-up in Pabo
- Green for unleaded and black for diesel is normal in the UK — yet not on each forecourt. Go by the label on the petrol pump, not the colour.
- The first fill in an unfamiliar car is the time to check the filler flap — inside it, or on the cap, many cars state the fuel they take.
- Good intentions count for less than a sticker or a fob in a vivid colour on your diesel's key when a house has one of each. So mark it.
- It sounds daft and it does the trick: on your first fill in a new or hired car, say "diesel" aloud before you take the nozzle off the petrol pump.
- Tuck the phone away. This is an easy mistake to make while you're thinking about something else.
- Up to a point, a misfuel inhibitor helps: some diesels come with a filler built to reject a petrol nozzle, and aftermarket devices exist for the rest. Treat it as a backstop, and keep reading the pump.
- Stop as soon as you notice. Less petrol in the tank makes a thinner mixture. It doesn't change what to do next, which is still not to crank it.
Put petrol in a diesel around Pabo already?
In that case, there is just a short order of things. Don't turn the ignition on, and do not start it. Ask the attendants to help you push it clear of the pump if you are still at the forecourt, whether that is Shell or anywhere else. Next, 0333 366 0103. We'll ask what got in, roughly how much, and if it has been run.
If it was AdBlue instead of petrol, say so. That's a different fault — corrosion and deposits and not lost lubrication — and it has its own page for Pabo.
What makes one Pabo petrol in a diesel job cost more than the next
There is no fair single quote for this, because the four scenarios above are four separate jobs. Which of them you are in is chiefly what moves your cost. Where the vehicle is counts too, and whether a van can safely reach it, after the proportion of petrol to what your tank holds.
That's why our engineers ask three questions before quoting rather than after: what went in, how much, and if it's run. Their answers are what change a range into one firm number.
About Pabo and where it is
Pabo is a small coastal locality in Conwy, Wales, situated near the towns of Llandudno Junction and Bangor. Pabo lies at an elevation of 37 metres, close to the shoreline and within a short distance of nearby villages such as Esgyryn and Bryn Pydew. Pabo is characterised by its predominantly detached housing stock, reflecting its residential nature. Pabo is home to a population of around 804 people, according to recent estimates.
Pabo and Conwy: where our fuel drain cover runs
Pabo rests in the LL postcode area, and our teams that answer petrol in diesel call-outs there work the locations near it as well — Esgyryn, Llandudno Junction and Bryn Pydew among them. We drain where your vehicle is — your own driveway, a lay-by, a supermarket car park, a forecourt — so it does not have to come to us.
In Pabo and still at the petrol pump?
Nothing beats it: that is where you are. Turned off it stays; then phone.