Clabby: Petrol in a Diesel Car? How Worried to Be
Far less than you likely are, if it hasn't been started. Everyone around Clabby begins with "have I wrecked it?", and the honest answer is usually no: petrol left inside that tank of a diesel remains harmless until priming, cranking or driving pulls it into the fuel system. Petrol in Diesel is who to phone, with the motor kept off, so it stays that way. Below, 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.
Your engine and petrol in a diesel: what happens
Diesel has two tasks on its way through a motor. Before it combusts, it lubricates — and then it ignites. What stops the surfaces inside the high-pressure fuel pump and your injectors from wearing down against one another is the diesel passing through them — they're built to very fine gaps.
The second job petrol does not do at all, and the first it does badly. Being less viscous than diesel, petrol strips out the protection a fuel system needs, so a pump on that mixture to wear itself. It is equally made to resist igniting under compression — the reverse of what a diesel needs — which is why you get the clattering.
Combined, those make the shape of the problem plain. Contact does not do the damage — movement does. A tank with petrol in it is a fuel problem. A pump that has been working on that petrol is the beginning of a mechanical one, and whatever a worn pump sheds travels on with your fuel to your injectors downstream.
Clabby, petrol in a diesel: four situations, from mild to major
The best case there is: filled up, never started. Being on a forecourt is what makes this possible: elsewhere, your car has been driven there to begin with. With the petrol kept in the tank alone, it's cleared and purged right where it stands, and nothing more is needed.
A moment's running, or merely the ignition on. Once primed, the fuel system has pulled petrol from your tank up to your filter and the lines. That's generally still a straightforward job — a drain, a flush, and your filter seen to.
Driven a few miles. Now your pump has spent those miles working on thinned fuel. Tank, lines, filter, then fresh fuel run through the entire circuit: that's this work, and the way the car was driven counts as much as the mileage. On the school run to the local primary school, the miles is short. Getting as far as Armagh, under 50 miles away, makes a very different job — as does any distance on the M77, over 50 miles from Clabby, with the motor working hard all the way.
Clattering, an uneven idle, smoke, a throttle gone soft: driven until it complained. The fuel is not acting like diesel any more, and your engine is telling you. Stop wherever you are — the verge on B842, a lay-by, a side street — and leave the vehicle where it is. The drain and flush still go first, and they take care of it: if a vehicle is stopped soon, long-term damage is very unusual.
What Clabby 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 will be." Nothing comes out when you top up — your tank just holds more of the same mixture. That guidance assumes a diesel fuel system handles petrol by percentage. It doesn't.
If anything, the opposite holds. Myth: "A modern diesel can cope with a bit of petrol." At higher pressure, through smaller parts: that's how a newer diesel moves its fuel, and so the protection matters more, not less.
This is the one that fools people. Myth: "If it starts and drives, there is no damage done." A petrol engine fed diesel usually won't run, and so the driver stops and the damage stops with them. Feed petrol to a diesel and it usually fires up, ticks over and drives away like nothing has happened — all the while its pump is wearing. Running isn't the same as fine.
Myth: "Add some two-stroke oil and drive the car home." It's an old fix for a different issue. What petrol has thinned stays diluted, and that petrol stays inside your tank anyway.
"Drain it yourself and you are sorted" — a myth, because after it has been running some petrol lies in the filter and lines, waiting to go straight back through your pump on the next start. Besides, petrol drained into a can by the road is truly dangerous.
Petrol in a diesel: how does it take place?
On purpose? Never. Through carelessness? Seldom, if ever. A diesel nozzle mostly won't fit a petrol motor, yet the narrower petrol nozzle goes into the filler of a diesel nearly without resistance — so forecourts make this one error easy, and just in one direction.
The moment habit stops matching your car is the moment it happens. Courtesy car, hire car, or a motor that's brand new. One petrol and one diesel on the drive of the same household. Your normal forecourt, its pumps suddenly in a different order. Racing for a train outside the nearest station and fuelling up en route. A new-to-you diesel Volkswagen Golf, its first fuelling, and a motorist accustomed to petrol: precisely when it happens. Add rain, a phone call or a back seat full of children, and the hand does what it has always done.
Next time you fill up around Clabby: avoiding petrol in a diesel
- Check the petrol pump, not the colour. In the UK unleaded handles are usually green and diesel black, yet not on every forecourt. The label is what matters.
- The first fill in a new car is the time to check the filler flap — inside it, or on the cap, many cars state the fuel to use.
- Good intentions count for less than a sticker or a fob in a bright colour on the diesel's key when a home has one of each. So mark it.
- It sounds silly and it works: on your first fill in a new or hired car, say "diesel" out loud before you take the nozzle off the pump.
- Mistakes like this are easy to make while your mind is on something else, so your phone goes away.
- Up to a point, a misfuel inhibitor helps: some diesels come with a filler built to refuse a petrol nozzle, and add-on devices are available for the remainder. Treat it as a safety net, then keep checking the pump.
- The moment you notice, stop: less petrol in your tank means a thinner mix. What to do next does not change, though — still don't start the car.
Clabby: already put petrol in a diesel?
Short and simple, then, is the order of things. Never crank it, and do not turn the ignition on. Yet at the forecourt, at the nearest petrol station or anywhere else? Ask the attendants to help you push the car away from the pump. Next, 0333 366 0103. We will ask what was put in, about how much, and if it's been run.
If it was AdBlue instead of petrol, say so. That's a different fault — corrosion and deposits rather than lost lubrication — and it has its own page for Clabby.
One petrol in a diesel task in Clabby costs more than another. Why?
Four different tasks sit behind the four situations above — which is why there's no fair single price. The scenario itself does most of the work of moving your cost. Two things come after that: the petrol that got in as a share of what that tank holds, then the spot the car is in and whether a technician can reach it safely.
Three queries come first, before quoting, rather than after — what got in, how much, has it run — and that is the reason. Their replies are what change a range into one firm number.
About Clabby, for a moment
Clabby is a small locality in County Fermanagh, situated inland at an elevation of 109 metres. Clabby lies near the villages of Fivemiletown, Tempo, and Brookeborough, and is approximately 29 miles from the city of Armagh. Clabby is characterised by its predominantly detached housing stock, reflecting its rural setting. Clabby is a relatively small community, with a population of around 697 people.
Clabby and County Fermanagh: where our fuel drain cover runs
Our teams answering petrol in diesel call-outs around Clabby, in the BT postcode area, equally work the places around it, Fivemiletown, Tempo and Brookeborough included. Our engineers drain where the vehicle is — your own drive, a lay-by, a supermarket car park, a forecourt — so it never needs to come to us.
At the pump around Clabby, right now?
The best position there is, then — that is where you are. Turned off it stays; then call.