Slingsby: Petrol in a Diesel Car? How Worried to Be
Less than you likely are, provided it has not been started. Everyone around Slingsby begins with "have I wrecked it?", and the fair answer is normally no: petrol left in your tank of a diesel stays harmless until priming, cranking or driving pulls it into the fuel system. To leave the vehicle that way, ring Petrol in Diesel then leave the motor alone. What petrol really does to a diesel, how to judge how far it has travelled, and how to stop it from happening again: that is the remainder of this page.
Petrol in a diesel: what does it do to the engine?
Two tasks fall to diesel on its route through a motor. Oiling comes before burning; it does both. The high-pressure fuel pump and your injectors are made to extremely fine gaps, and the diesel passing through them is what stops those surfaces from wearing against one another.
The second job petrol doesn't do at all, and the first it does poorly. Being less viscous than diesel, petrol strips away the protection a fuel system needs, leaving a pump on that mixture wearing itself. It's equally made to resist igniting under compression — the opposite of what a diesel needs — which is where you hear the rattling.
Seen together, they make clear the shape the issue takes. The harm is done by circulation, not by contact. All a tank with petrol in it amounts to is a fuel issue. After your pump has been working on that petrol, a mechanical issue has begun: anything shed by a pump that's grinding travels onward to the fuel injectors with your fuel.
Four scenarios we see around Slingsby: how serious is petrol in a diesel?
Filled up, and never started: no case is better. On a forecourt, and truly only there, that petrol is still confined to that tank — because anywhere else the vehicle was driven to get to it. The job is draining and rinsing on the spot.
Started for a moment, or just the ignition on. Once primed, the system has pulled petrol out of that tank as far as the fuel filter and the fuel lines. That's normally still a simple job — a drain, a flush, and your filter dealt with.
Those few miles driven meant the pump working on fuel thinned by petrol the whole way. Tank, lines, filter, then clean fuel put through the entire circuit: that's this work, and the way the vehicle was driven counts as much as the miles. Short trips, such as the school run to Slingsby Community Primary School, are one matter. Any mileage on the A1(M), under 25 miles from Slingsby, means your engine working hard throughout, and a run to York, under 25 miles away, is a very different job too.
Driven on until it complained — clattering, smoke, a ragged idle, a dead throttle. The motor is telling you the fuel is no longer behaving like diesel. Whether it's the verge on Green Dyke Lane, a lay-by or a side street, stop where you are and leave it. A car pulled over quickly very seldom has lasting damage, since the fuel drain and the flush, which still come first, sort it out.
What Slingsby drivers get told about petrol in a diesel — and the myths in it
"Top it up the rest of the way with diesel and it will be fine" — a myth. It will not. Nothing is removed by topping up — you are left with a fuller tank, still the same mixture. A diesel fuel system doesn't accept petrol by percentage in the way that advice assumes.
If anything, the opposite is true. Myth: "A newer diesel can cope with a bit of petrol." Smaller parts and higher pressure are how a newer diesel runs its fuel, and that makes the protection count more, not less.
This is the one that catches people. Myth: "If it starts and drives, there is no damage done." The driver of a petrol motor fed diesel usually stops, because it will not run, and the harm stops with them. Nothing looks to have happened when a diesel fed petrol fires up, ticks over and drives away, which it usually will; meanwhile the pump grinds. Fine and running are not the same thing.
Myth: "Add some two-stroke oil and drive the vehicle home." It's an outdated workaround for a different fault. It does not put back what petrol has diluted, and that petrol is still inside your tank later on.
The next start sends petrol back round your pump from the fuel lines and your filter, where some of that ends up once your engine has been run. That's why draining the tank yourself doesn't sort it — a myth. It's also genuinely risky to drain petrol into a can by the roadside.
How it happens: petrol in a diesel
A careless moment is rarely the cause, and no one means to do it. The petrol nozzle is the narrower of the two and slides into a diesel filler with almost no resistance; a diesel nozzle mostly will not go into a petrol vehicle at all. The forecourt makes it easy, and the slip runs one way.
When routine and the vehicle stop matching, it takes place. A 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 driveway. The pumps in a different order on a familiar forecourt. A train to catch, and a rushed fill en route to Malton. Precisely the moment it occurs: after years of driving petrol, a driver fills a diesel Volkswagen Golf for the first time. Add a back seat full of children, a phone call or rain, and habit wins.
Next time you fill up in Slingsby: avoiding petrol in a diesel
- Not every forecourt in the UK follows green for unleaded and black for diesel, even if most usually do. Check the pump's label; the colour is just a hint.
- The first fill in an unfamiliar motor is the time to check the filler flap — on it, or on the cap, plenty of motors state the fuel they take.
- Good intentions count for less than a sticker or a fob in a bright colour on the diesel's key when a household has one of each. So mark it.
- Before the nozzle leaves the pump the first time you fuel a hired or new motor, say "diesel" out loud. Silly, perhaps, but it does the trick.
- Tuck the phone away. This is an easy mistake to make whilst you're thinking about something else.
- Add-on devices exist for motors without one, and some diesels come with a filler that will not accept a petrol nozzle. Helpful — but a backstop at best, never a reason to stop checking the label.
- Stop the moment you notice. Less petrol in your tank makes a thinner mix. It does not change what to do next, which is still not to crank it.
Put petrol in a diesel in Slingsby already?
Short and simple, then, is the order of things. Never start it, and don't turn the ignition on. If you are still on the forecourt — the nearest petrol station or anywhere else — ask the staff to help you push it clear of the pump. Then phone 0333 366 0103 and tell us what went in, roughly how much, and if it's run.
Corrosion and deposits form the problem with AdBlue, whereas petrol means lost lubrication. So if it was AdBlue, say so — and see its own Slingsby page.
Why one petrol in a diesel task around Slingsby costs more than another
Four separate jobs lie behind the four scenarios above — which is why there's no fair single quote. Which of them you're in is chiefly what moves the cost. Two things come after that: the petrol that went in as a proportion of what the tank takes, then the spot your car is in and whether our van can reach it safely.
Three queries come first, before any quote, instead of after — what went in, how much, has it run — and that is the reason. The replies change a range into a straight figure.
About Slingsby itself
Slingsby is a village in North Yorkshire, situated on the banks of a river at an elevation of 33 metres, approximately 15 miles from the city of York. Slingsby has a mix of housing types, with semi-detached homes being the most common, and is surrounded by other small villages such as Fryton and Barton-le-Street. Slingsby is located in a rural area, with the nearest major city being York, and is about 187 miles north of London.
Fuel drain cover across North Yorkshire, Slingsby included
Slingsby sits in the YO postcode area, and our teams that answer petrol in diesel jobs there work the places around it as well — Fryton, Wath and Barton-le-Street among them. You need not move the vehicle to us. Forecourts, supermarket car parks, lay-bys and your own driveway are all spots where we work.
In Slingsby and still at the petrol pump?
Nothing beats it: that is where you now are. Phone, and keep it switched off.