Islandmagee: Petrol in a Diesel Car? How Worried to Be
Likely less than you are now — as long as nobody has started the car. Everyone around Islandmagee starts with "have I wrecked it?", and the fair answer is normally no: petrol resting inside that tank of any diesel remains harmless till priming, cranking or driving draws it into the system. To keep it that way, call Petrol in Diesel and leave your engine switched off. What petrol actually does to a diesel, how to gauge how far it's gone, and how to stop it from happening a second time: that's the rest of this page.
Petrol in a diesel: what does it do to the motor?
Passing through a motor, diesel is doing two things at the same time. Before it combusts, it lubricates — and then it ignites. What stops the surfaces inside the high-pressure fuel pump and your injectors from wearing against one another is the diesel passing through them — they're designed to very fine tolerances.
The second task petrol does not do at all, and the first it does poorly. It's runnier than diesel and strips away the protection the fuel system depends on, and so a pump running on a petrol mix is a pump wearing itself. And petrol is made to resist igniting under compression, which is the opposite of what a diesel needs from its fuel. That's where the knocking comes from.
The shape of the problem is plain once you put those together. Contact does not do the damage — circulation does. Petrol in a tank is a fuel issue. A pump that has been running on that petrol is the start of a mechanical one, and whatever a worn pump sheds moves on with the fuel to the fuel injectors downstream.
Islandmagee, petrol in a diesel: four cases, from mild to major
Filled up, not once started. The best case there is. Only that tank has petrol in it, so the job is clearing your tank and purging the system where the vehicle stands. This scenario can only really happen on a forecourt: anywhere else, the vehicle got there by being driven.
Started for a second, or only the ignition on. With the system primed, the lines and filter already contain petrol that came from that tank. That is generally still a simple task — a drain, a flush, and the filter dealt with.
Those few miles on the road were the pump labouring on fuel weakened by petrol throughout. Tank, lines, filter, then fresh fuel put through the whole system: that is this work, and the way your car was driven matters as much as the distance. A school run to the local primary school is one thing. Any miles on the M77, over 50 miles from Islandmagee, means the engine has worked hard throughout, and a run to Belfast, under 25 miles away, is a very different job as well.
Driven till it protested. Rattling, a ragged idle, smoke, a throttle that has gone soft. The motor is telling you the fuel is no longer behaving like diesel. Pull up wherever you are — the verge on Heugh Road, a lay-by, a side street — and leave it there. The fuel drain and flush-through still go first, and they deal with it: if a vehicle is pulled over quickly, lasting damage is very unusual.
Myths Islandmagee people hear about petrol in a diesel
"Top it up the rest of the way with diesel and it will be fine" — a myth. It will not. Nothing is removed when you top up — your tank just carries more of the same mixture. That guidance supposes a diesel fuel system handles petrol by percentage. It does not.
Myth: "A modern diesel can cope with a bit of petrol." If anything, the opposite. At higher pressure, through finer parts: that's how a modern diesel handles its fuel, and so the protection matters more, not less.
Myth: "If it starts and drives, there is no harm done." This is the one that fools motorists. Feed diesel to a petrol engine and it usually won't run, so the driver stops — and the harm stops with them. A diesel fed petrol generally starts, idles and drives away as though nothing has happened, while your pump wears. Running isn't the same as fine.
An outdated workaround for a separate issue lies behind this one. Myth: "Add some two-stroke oil and drive it home." That petrol is still inside that tank after that, and what it has thinned is not put back.
The next start sends petrol back round your pump out of the lines and the filter, where some of it ends up once the motor has been run. That is why a DIY tank drain does not leave you sorted — a myth. Clearing petrol into a can by the kerbside is also truly risky.
Petrol in a diesel: how does it take place?
On purpose? Never. Through carelessness? Rarely, if ever. The forecourt makes it simple: the petrol nozzle is the slimmer of the two, and it slips into a diesel filler with almost no resistance, whilst a diesel nozzle generally will not go into a petrol vehicle at all. So the mistake runs one way.
The moment routine stops matching your car is the moment it takes place. Any motor that's new to you — hired, on loan as a courtesy car, or just bought. A household with one petrol and one diesel on the drive. A forecourt you know, but with its pumps laid out differently. Rushing for a train outside the nearest station and filling up en route. Years of petrol cars behind you, a diesel Volkswagen Passat in front of you on the forecourt for its first tank — that's when. With rain, a call arriving, or children to deal with, the hand simply does what it always has.
Preventing petrol in a diesel next time you fill up in Islandmagee
- The label is what matters, so read the petrol pump rather than the colour: in the UK unleaded handles are usually green and diesel black, yet not on each forecourt.
- Plenty of vehicles state the fuel type inside the filler flap or on the cap, and so check it on your first fill in any motor you do not know.
- One of each in the household? Label the key to your diesel — a bright fob, a sticker — since intending to remember is not enough.
- Before the nozzle leaves the petrol pump the first time you fuel a hired or new car, say "diesel" out loud. Silly, perhaps, yet it does the trick.
- Tuck your phone away. This is an easy mistake to make while you are thinking about something else.
- A misfuel inhibitor helps, up to a point. Some diesels have a filler designed to refuse a petrol nozzle, and add-on devices are available for motors without one. They are a backstop, not a reason to stop reading the pump.
- The moment you realise, stop: less petrol in that tank makes a thinner mix. What to do next does not change, though — still do not crank it.
Put petrol in a diesel in Islandmagee already?
Then the order of things is short. Do not fire it up, and don't switch the ignition on. The staff at the forecourt — whether at the nearest petrol station itself or wherever you filled up — will usually help push it away from the petrol pump if you ask. Next, 0333 366 0103. We'll ask what went in, about how much, and if it's been run.
Say so if it was AdBlue rather than petrol: it's a separate problem, with its own page for Islandmagee, because AdBlue brings corrosion and deposits instead of lost lubrication.
What makes one Islandmagee petrol in a diesel job cost more than the next
A fair single price does not exist here: four scenarios, four separate jobs. What moves the cost is mostly which of them you're in. Where your car is counts too, and whether a technician can safely get to it, after the proportion of petrol to what the tank takes.
That is why we ask three queries before quoting rather than after: what got in, how much, and if it's run. Those replies change a range into a straight figure.
About Islandmagee, briefly
Islandmagee is a coastal locality in County Antrim, situated near the towns of Ballystrudder and Ballycarry, with Mill Bay to the north. Islandmagee sits on the eastern coast of Northern Ireland, approximately 16 miles from Belfast, and has a population of around 881 residents. Islandmagee is characterised by its detached housing and elevated position, with an average elevation of 114 metres above sea level. Islandmagee is also relatively distant from major cities like London, being around 324 miles away.
Fuel drain cover across County Antrim, Islandmagee included
Our teams answering petrol in diesel call-outs around Islandmagee, in the BT postcode area, equally work the spots near it, Ballystrudder, Ballycarry and Mill Bay included. A forecourt, a supermarket car park, a lay-by or your own driveway are all spots our engineers work, and your car doesn't need to come to us.
Still at the petrol pump in Islandmagee?
No position is better: that's where you now are. Keep the vehicle turned off, and ring.