Should You Worry? Petrol in a Diesel Car in Great Abington
Likely less than you already are — as long as nobody has started it. "Have I wrecked it?" is the first question anyone in Great Abington asks, and the truthful answer is generally no, because petrol left in a diesel tank hurts nothing until it is drawn through your fuel system — by ignition priming, by your starter, or by driving. To keep the vehicle that way, ring Petrol in Diesel and leave the motor switched off. The rest of this page sets out what petrol actually does to a diesel, how to tell how far it has got, and how to make sure it doesn't happen to you again.
Petrol in a diesel: what does it do to your engine?
Passing through an engine, diesel is doing two jobs at the same time. It combusts, and before it combusts it lubricates. What keeps the surfaces inside your high-pressure pump and your injectors from wearing down against one another is the diesel flowing through them — they are designed to extremely fine clearances.
The second task petrol does not do at all, and the first it does badly. Being less viscous than diesel, petrol strips out the lubrication a fuel system needs, so a pump running on the blend wearing itself. It's equally made to resist igniting under compression — the opposite of what a diesel needs — which is why you get the knocking.
Put those together and the shape of the issue is plain. Not contact but circulation is what causes the damage. All a tank with petrol in it amounts to is a fuel issue. Whatever a worn pump sheds goes on, borne by the fuel, into the fuel injectors further along, which is why a pump that has worked on the petrol is where a mechanical problem begins.
Petrol in a diesel around Great Abington: how bad is it? Four situations
The best case there is: filled up, never started. Being at a forecourt is what makes this possible: elsewhere, your car has been driven there to begin with. With the petrol kept in your tank alone, it is cleared and rinsed right where it stands, and nothing more is needed.
Ignition on, or started for a moment. Petrol has come out of that tank and reached the fuel filter and the fuel lines, since the fuel system has been primed. That's normally still a straightforward job — a drain, a flush, and the fuel filter seen to.
Driven a couple of miles. Now the pump has spent these miles working on diluted fuel. How hard the vehicle was driven counts as much as how far, and this work takes in your tank, your lines, the fuel filter and fresh fuel through the entire circuit. Driving the kids to Great Abington Primary School is one kind of trip. Very different again: a run to Cambridge, under 10 miles away, or any mileage on the M11, under 3 miles from Great Abington, where the engine kept working hard.
It complained, and only then stopped: smoke, rattling, a throttle gone soft, an idle gone lumpy. What you are hearing is your engine signalling fuel that no longer behaves like diesel. Leave it wherever it stops: a lay-by, a side street, the verge on Newmarket Road. The fuel drain and flush still go first, and they sort it out: when a car is stopped soon, lasting damage is very rare.
What Great Abington drivers get told about petrol in a diesel — and the myths in it
It will not be fine. The myth: "Fill it the rest of the way with diesel and it will be." Nothing is removed by topping up — you are left with a fuller tank, still the same mixture. That guidance assumes a diesel fuel system handles petrol by percentage. It does not.
If anything, the opposite is true. Myth: "A current diesel can cope with a bit of petrol." A current diesel runs its fuel through smaller parts at higher pressure, which makes the lubrication matter more, not less.
This is the one that catches drivers. Myth: "If it starts and drives, there's no damage done." Diesel in a petrol motor generally means a motor that will not run: the driver stops, and so does the damage. Feed petrol to a diesel and it normally fires up, idles and pulls away like nothing happened — all while its pump wears. Fine and running aren't the same thing.
"A drop of two-stroke oil and drive it home" — a myth, taken from a fix from years ago, for a separate problem. What petrol has weakened stays diluted, and that petrol stays in the tank anyway.
The next start sends petrol back round your pump out of the fuel lines and your filter, where some of it sits after your engine has run. That is why a DIY tank drain doesn't leave you sorted — a myth. Emptying petrol into a can by the kerbside is also genuinely risky.
How does petrol in a diesel take place?
On purpose? Never. Through carelessness? Seldom, if ever. The forecourt makes it simple: the petrol nozzle is the narrower of the two, and it slips into a diesel filler with almost no resistance, while a diesel nozzle generally will not go into a petrol vehicle at all. So the slip runs one way.
The moment habit stops matching the vehicle is the moment it occurs. A car that's new to you — a hire car, on loan as a courtesy car, or just bought. One petrol and one diesel on the drive of the same household. A well-known forecourt with the pumps in a different order. Rushing for a train at Whittlesford Parkway and fuelling up en route. Precisely the moment it takes place: after years of driving petrol, a driver fills a diesel Volkswagen Passat for the first time. Your hand repeats what it has always done once you add rain, a phone call or a back seat full of kids.
Next time you fill up around Great Abington: preventing petrol in a diesel
- Not every forecourt in the UK follows green for unleaded and black for diesel, though most usually do. Read the pump's label; the colour is just a hint.
- The first fill in an unfamiliar vehicle is the time to check your filler flap — inside it, or on the cap, many cars state which fuel to use.
- Label your key. In a house with one of each, a coloured fob or a sticker on the diesel's key does more than any amount of meaning to remember.
- Before the nozzle leaves the pump the first time you fill a hired or new motor, say "diesel" aloud. Daft, perhaps, yet it does the trick.
- Mistakes like this are easy to make whilst your mind is on something else, so the phone goes away.
- A misfuel inhibitor helps, up to a point. Some diesels come with a filler designed to block a petrol nozzle, and add-on devices exist for vehicles without one. They are a backstop, not a reason to stop checking the petrol pump.
- As soon as you notice, stop: less petrol in the tank makes a thinner blend. What to do next does not change, though — still don't start the vehicle.
Put petrol in a diesel in Great Abington already?
Short and simple, then, is the order of things. Starting it is out, and so is switching on your ignition. The attendants at the forecourt — whether at Shell itself or wherever you filled up — will normally help roll it away from the petrol pump if you ask. Then ring 0333 366 0103 and tell us what went in, roughly how much, and whether it has run.
Say so if it was AdBlue instead of petrol: it is a different fault, with its own page for Great Abington, since AdBlue brings corrosion and deposits rather than lost protection.
Great Abington petrol in a diesel jobs: why one costs more than another
The four situations above are four different tasks, so no single price for this would be honest. Which of them you are in is mostly what shifts your cost. Two things follow that: the petrol that went in as a share of what the tank takes, then the place the car is in and whether our van can reach it safely.
That's why our engineers ask three queries before quoting rather than after: what was put in, how much, and if it has run. Those answers turn a range into a straight figure.
About Great Abington itself
Great Abington is a small village in Cambridgeshire, situated on the banks of the River Granta at an elevation of around 37 metres. Great Abington lies close to the city of Cambridge, about 7 miles to the southeast, and is part of a network of rural communities including Little Abington, Babraham, and Pampisford. Great Abington has a population of approximately 514 people, living in predominantly detached houses. Great Abington is also within commuting distance of London, about 45 miles to the southwest.
Across Cambridgeshire and around Great Abington: fuel drain cover
Great Abington waits in the CB postcode area, and the teams that answer petrol in diesel call-outs there work the spots near it as well — Little Abington, Babraham and Pampisford among them. Our engineers drain where your car is — your own drive, a lay-by, a supermarket car park, a forecourt — so it does not have to come to us.
In Great Abington and still at the petrol pump?
The best spot there is, then — that is where you are. Keep the vehicle switched off, then ring.