Childrey: Petrol in a Diesel Car? How Worried to Be
Probably less than you are now — provided no one has started the vehicle. Petrol sitting in a diesel tank does nothing to your motor until something pulls it through your fuel system — your ignition priming the pump, your starter, or the drive on its own. So the honest answer to the first query anyone in Childrey asks, "have I wrecked it?", is normally no. Leave the engine off and ring Petrol in Diesel — that keeps it like that. What petrol really does to a diesel, how to gauge how far it has gone, and how to stop it from happening a second time: that's the rest of this page.
Inside the engine: what petrol in a diesel does
Two tasks fall to diesel on its journey round a motor. Before it combusts, it lubricates — and then it combusts. Very fine clearances go into your injectors and your high-pressure pump, and just the diesel running through keeps those surfaces from grinding together.
Of these two tasks, petrol manages the first poorly and the second not at all. It is runnier than diesel and removes the protection the system depends on, and so a pump running on a petrol blend 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 is where the knocking comes from.
Put these together and the shape of the issue is plain. Not contact but movement is what causes the damage. Any tank with petrol in it is a fuel issue. A pump that has been working on that petrol is the start of a mechanical one, and whatever a worn pump sheds moves on with your fuel to the fuel injectors downstream.
Childrey, petrol in a diesel: four situations, from mild to major
Filled up, not once started. The best case there can be. On a forecourt, and genuinely only there, that petrol is still confined to the tank — since anywhere else your car was driven to get to it. The task is draining and purging on the spot.
The ignition turned on, or a short start. The system has been bled, so petrol has left the tank and got to the fuel filter and the fuel lines. Drain, flush, deal with the filter: still usually easy.
Some miles driven, and the pump has spent each of them running on weakened fuel. Distance is only half of it; how hard it was driven counts equally. Either way this work runs to your tank, the lines, the fuel filter and fresh fuel through the whole system. Driving the children to The Ridgeway Church of England (C) Primary School is one kind of trip. A run as far as Oxford, under 15 miles away, is a very different job. So is any miles on the M4, under 10 miles from Childrey, where your engine has been working hard throughout.
It complained, and only then stopped: smoke, knocking, a throttle gone soft, an idle gone ragged. That's the engine telling you its fuel no longer is behaving like diesel. Whether it's the verge on Chapel Way, a lay-by or a side street, stop there and leave it. A vehicle pulled over quickly very seldom has long-term damage, since the fuel drain and the flush, which still go first, sort it out.
What Childrey 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." Topping up takes out nothing; it gives you a fuller tank of the same mix. The idea behind that guidance — that diesel fuel systems tolerate petrol by percentage — is wrong.
If anything, the reverse is true. Myth: "A modern diesel can cope with a bit of petrol." A modern diesel sends its fuel through more precise components at higher pressure, which makes the protection matter more, not less.
This is the one that fools motorists. Myth: "If it starts and drives, there is no damage done." A petrol engine fed diesel usually will not run, so the motorist stops and the damage stops with them. A diesel fed petrol normally starts, idles and drives away as if nothing has happened, while the pump grinds. Fine and running are not the same at all.
"A drop of two-stroke oil and drive it home" — a myth, taken from a fix from years ago, for a different fault. None of what petrol diluted gets put back by it — and afterwards, that tank still holds the petrol.
Myth: "Drain the tank yourself and you're sorted." Once your engine has run, some of the petrol is no longer inside that tank: it's in the filter and the fuel lines, and it goes straight back through the pump on your next start. Emptying petrol into a can by the kerbside is also truly dangerous.
How it happens: petrol in a diesel
Carelessness is seldom the cause, and no one means to do it. One way only, since of the nozzles: the slimmer petrol one slips inside a diesel filler with almost no resistance, while the diesel one generally won't fit a petrol motor. That's how the forecourt makes it straightforward.
The moment routine stops matching the car is the moment it takes place. Hire cars, courtesy cars, and cars that are new to you. Households running one of each, petrol and diesel. Your usual forecourt, its pumps suddenly in a different order. A train to catch, and a hurried fill en route to Didcot Parkway. Precisely the moment it happens: after years of driving petrol, someone fills a diesel Volkswagen Passat for the first time. With rain, a call arriving, or children to deal with, your hand simply does what it has always done.
Childrey motorists: how to avoid petrol in a diesel next time
- The label is what counts, so check the petrol pump instead of the colour: in the UK unleaded handles are normally green and diesel black, but not on each forecourt.
- The first fill in a new motor is the time to check the filler flap — on it, or on the cap, many vehicles state the fuel they take.
- One of each in the household? Label the key to the diesel — a coloured fob, a sticker — because intending to remember isn't enough.
- "Diesel", out loud, before you lift the nozzle — each time a new or hired car gets its first tank. It seems daft. It does the trick.
- Whilst you're thinking about something else, this is an easy mistake to make — so put the phone away.
- Some diesels have a filler designed to reject a petrol nozzle, and devices you can add are available for cars without one. Such an inhibitor helps up to a point — as a safety net, not a reason to stop reading the petrol pump.
- The moment you realise, stop: less petrol inside your tank makes a weaker mix. What to do next doesn't change, though — still do not fire it up.
Childrey: already put petrol in a diesel?
Short and simple, then, is the order of things. Don't switch the ignition on, and do not fire it up. Ask the staff to help you push it clear of the pump if you're still at the forecourt, whether that's Mellors of Challow or anywhere else. Then ring 0333 366 0103 and tell us what went in, about how much, and whether it's run.
If it was AdBlue and not petrol, say so. That is a different problem — corrosion and deposits rather than lost lubrication — and it has its own page for Childrey.
What makes one Childrey petrol in a diesel task cost more than the next
Four separate tasks lie behind the four scenarios above — which is why there's no honest single quote. What shifts the cost is chiefly which of them you are in. Where the car is counts too, and whether a technician can safely get to it, after the ratio of petrol to what that tank takes.
Three questions come first, before any quote, rather than after — what went in, how much, has it run — and that is the reason. Their replies are what change a range into one firm number.
About Childrey, briefly
Childrey is a small village in Oxfordshire, situated in the South East of England, with an elevation of around 111 metres. Childrey lies approximately 14.9 miles from Oxford and 58.3 miles from London, placing it in a rural setting with nearby villages including West Challow and Sparsholt. Childrey has a population of around 527 people, predominantly living in detached houses. Childrey is surrounded by rolling countryside, characteristic of the Oxfordshire landscape.
Fuel drain cover in Childrey and across Oxfordshire
The teams answering petrol in diesel calls in Childrey, in the OX postcode area, also work the locations around it, West Challow, Sparsholt and Townsend among them. You need not bring the vehicle to us. Forecourts, supermarket car parks, lay-bys and your own driveway are all spots we drain.
Childrey: still at the pump?
The best place there is, then — that's where you are. Turned off it remains; then phone.