How Worried Should You Be? Petrol in a Diesel Car in Shepshed
Not started? Then less worried than you likely are. Petrol resting in a diesel tank does nothing to the motor till something pulls it through the system — your ignition priming the pump, your starter, or the drive on its own. So the fair answer to the first query anyone around Shepshed asks, "have I ruined it?", is generally no. Petrol in Diesel is who to ring, with your engine left off, so it stays that way. The rest of this page sets out what petrol really does to a diesel, how to tell how far it has got, and how to make sure it does not happen to you again.
Inside your engine: what petrol in a diesel does
Two tasks fall to diesel on its route through a motor. It lubricates to begin with, and only then does it burn. Your high-pressure pump and the fuel injectors are designed to extremely fine gaps, and your diesel passing through them is what keeps those surfaces from wearing against one another.
Of these two jobs, petrol handles the first poorly and the second never. It is thinner than diesel and strips away the protection the fuel system hinges on, 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.
The shape of the trouble is plain when you put those together. Not contact but movement is what causes the damage. Where that petrol is only inside the tank, it's a problem of fuel, nothing more. After your pump has been working on that petrol, a mechanical problem has begun: whatever is shed by a pump that is wearing down is carried downstream to the injectors with your fuel.
Petrol in a diesel in Shepshed: how serious is it? Four cases
Filled up, and not started: no case is better. That petrol is inside your tank and just the tank, and the job is a drain and a flush where the vehicle sits. This is the one scenario that can only really occur on a forecourt, because anywhere else the car has been driven to get there.
A moment's running, or merely your ignition on. Petrol has left that tank and got to your filter and the lines, because the system has been primed. That is usually still a simple job — a drain, a flush, and the filter seen to.
A couple of miles driven, and your pump has spent each of them working on thinned fuel. Tank, lines, filter, then fresh fuel put through the whole system: that's this work, and the way the vehicle was driven counts as much as the mileage. On the school run to Saint Winefride's Catholic Voluntary Academy, Shepshed, Leicestershire, the miles is small. Driving as far as Leicester, under 15 miles away, makes a very different job — as does any distance on the M1, under a mile from Shepshed, with the motor running hard the whole time.
Driven on until it complained — knocking, smoke, an uneven idle, a soft throttle. That is your engine telling you its fuel has stopped behaving like diesel. Leave it wherever it has stopped: a lay-by, a quiet street, the verge on Field Street. A vehicle pulled over quickly very seldom has lasting damage, as the fuel drain and the flush, which still come first, deal with it.
Petrol in a diesel stories Shepshed motorists hear
It will not be fine. The myth: "Fill it the rest of the way with diesel and it will be." Topping up takes out nothing; it gives you a fuller tank of the same mix. The idea behind that advice — that diesel fuel systems tolerate petrol by percentage — is wrong.
Myth: "A current diesel can cope with a bit of petrol." If anything, the opposite. Protection counts more on newer diesels, not less, since their fuel runs through finer parts at higher pressure.
This is the one that catches motorists. Myth: "If it starts and drives, there's no harm done." The driver of a petrol engine fed diesel usually has no choice but to stop, because it will not run, and the damage stops there. Feed petrol to a diesel and it generally starts, idles and drives away like nothing has happened — all the while its pump wears. Fine and running aren't the same thing.
An outdated workaround for a distinct fault is behind this one. Myth: "Add some two-stroke oil and drive the car home." That petrol is still in that tank after that, and whatever it has weakened is not put back.
If the engine has been run, part of the petrol sits in the filter and the lines, not your tank — and your next start pulls it right back through the pump. So the myth "drain the tank yourself and you are sorted" doesn't hold. It is also truly risky to drain petrol into a can by the roadside.
How it happens: petrol in a diesel
On purpose? Never. Through carelessness? Seldom, if ever. One way only, because of the nozzles: the slimmer petrol one slides inside a diesel filler with almost no resistance, while the diesel one mostly won't fit a petrol motor. That's how the forecourt makes it straightforward.
The moment routine stops matching the vehicle is the moment it takes place. A car that's new to you — a hire car, on loan as a courtesy car, or just bought. Two cars on one driveway, one petrol, one diesel. The pumps in a different order on a familiar forecourt. Rushing for a train at Loughborough and fuelling up en route. A new-to-you diesel Volkswagen Golf, its first fuelling, and a motorist accustomed to petrol: exactly when it occurs. Throw in a back seat full of kids, a phone call or rain, and the hand wins.
Next time you fill up around Shepshed: avoiding petrol in a diesel
- Check the pump, not the colour. In the UK unleaded handles are normally green and diesel black, yet not on every forecourt. The label is what matters.
- In a motor you do not know, look inside the flap over the filler or at the cap before the first fill: plenty of cars state the fuel there.
- Label the key. In a home with one of each, a coloured fob or a sticker on the diesel's key does more than any amount of meaning to remember.
- "Diesel", aloud, before you lift the nozzle — every time a new or hired car gets its first tank. It sounds daft. 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 built to refuse a petrol nozzle, and add-on devices are available for motors without one. They are a safety net, not a reason to stop reading the pump.
- The moment you notice, stop: less petrol in that tank means a weaker mix. What to do next does not change, though — still do not fire it up.
Put petrol in a diesel in Shepshed already?
Then the order of things is brief. Leave it unstarted, with your ignition switched off too. Yet on the forecourt, at Esso or anywhere else? Ask the attendants to help you push the car away from the petrol pump. What was put in, about how much, and whether it's run: tell us that when you call 0333 366 0103.
Say so if it was AdBlue instead of petrol: it's a separate fault, with its own page for Shepshed, since AdBlue brings corrosion and deposits instead of lost lubrication.
One petrol in a diesel task around Shepshed costs more than another. Why?
The four scenarios above are four different tasks, so no single quote for this would be honest. The situation itself does most of the work of moving the cost. After that it's the share — how much petrol went in against how much the tank holds — and after that where the vehicle is and whether a van can get to it safely.
What went in, how much, and whether it has run — three questions our technicians ask before pricing, not after, for precisely that reason. Those answers turn a range into a straight figure.
About Shepshed itself
Shepshed is a town situated in the English county of Leicestershire, characterized by its inland location. It serves as a market town, providing local amenities and services. Located within the Charnwood Borough, Shepshed is a notable settlement in the area, with a significant presence near the larger town of Loughborough.
Fuel drain cover around Shepshed and across Leicestershire
Shepshed sits in the LE postcode area, and our teams that answer petrol in diesel jobs there work the spots near it as well — Ringing Hill, Nanpantan and Oaks in Charnwood among them. No need to move the car to us. Forecourts, supermarket car parks, lay-bys and your own drive are all spots we drain.
At the petrol pump around Shepshed, right now?
Then, you couldn't be in a better place. Leave the car switched off, then ring.