The Lings: Petrol in a Diesel Car? How Worried to Be
Likely less than you are now — as long as no one has started it. Till the ignition primes the pump, the starter cranks, or your car is driven, petrol in a diesel tank simply waits there and does no harm. Which means the honest reply to that first The Lings question — "have I ruined it?" — usually no. To leave it that way, ring Petrol in Diesel then leave your engine switched off. Further down, you will find what petrol actually does inside a diesel, how far it may have gone, and how to stop it happening to you a second time.
The motor and petrol in a diesel: what goes on
Diesel has two tasks on its way through an engine. Before it combusts, it lubricates — and then it ignites. Extremely fine tolerances go into the fuel injectors and your high-pressure pump, and only your diesel flowing through keeps their surfaces from grinding together.
Petrol does the first job poorly and the second not at all. Being less viscous than diesel, petrol strips out the lubrication a fuel system needs, so a pump on that mixture to wear itself. It's also made to resist igniting under compression — the opposite of what a diesel needs — which is where you hear the knocking.
The shape of the issue is clear once you put those together. The damage is done by movement, not by contact. A tank with petrol in it is a fuel issue. Whatever a worn pump sheds goes on, borne by the fuel, into your injectors further along, which is why a pump that has worked on the petrol is where a mechanical problem begins.
Four scenarios our engineers see in The Lings: how bad is petrol in a diesel?
Filled up, never started. The best case there can be. Just that tank has petrol in it, and so the job is clearing that tank and cleaning your system where your car stands. This scenario can only truly occur at a forecourt: anywhere else, the vehicle got there by being driven.
The ignition switched on, or a short start. Once primed, the fuel system has drawn petrol out of your tank up to the fuel filter and your lines. Drain, flush, deal with the filter: still normally easy.
Some miles driven, and your pump has spent every one of them working on weakened fuel. Mileage is only half of that; how hard it was driven counts equally. Either way the work includes your tank, your lines, the filter and clean fuel through the whole circuit. Short trips, such as the school run to Sheep Dip Lane Academy, are one thing. Any distance on the M18, under a mile from The Lings, means the motor has worked hard throughout, and a run to Doncaster, under 10 miles away, is a very different task as well.
It protested, and only then stopped: smoke, knocking, a throttle gone soft, an idle gone lumpy. The engine is telling you the fuel is no longer acting like diesel. Leave it where it stops: a lay-by, a quiet street, the verge on Lings Lane. A vehicle pulled over quickly very seldom has permanent damage, since the drain and the flush, which still go first, deal with it.
Petrol in a diesel stories The Lings motorists hear
Myth: "Fill it the rest of the way with diesel and it will be fine." It will not. A fuller tank of the same mixture is all it gives, since topping up takes out nothing. Percentage is not how a diesel fuel system tolerates petrol, whatever that guidance assumes.
"Current diesels can handle a little petrol" — a myth, and closer to the opposite. A newer diesel runs its fuel through finer components at higher pressure, which makes the lubrication count more, not less.
This is the one that fools drivers. Myth: "If it starts and drives, there is no harm done." Feed diesel to a petrol motor and it generally will not run, and so the driver stops — and the damage stops with them. A diesel fed petrol normally starts, ticks over and drives away as if nothing has happened, while your pump wears. Being able to run isn't the same as being fine.
Myth: "Add some two-stroke oil and drive the car home." It is an outdated workaround for a different fault. That petrol is still inside your tank after that, and whatever it has diluted is not put back.
The next start draws petrol back round the pump out of the fuel lines and your filter, where some of it sits after your engine has run. That is why draining the tank yourself doesn't leave you sorted — a myth. Clearing petrol into a can at the kerbside is also genuinely risky.
Why petrol in a diesel occurs so easily
No one does it on purpose, and it's rarely carelessness. 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 error runs one way.
Habit and the vehicle falling out of step is when it occurs. A motor that is new to you — a hire car, on loan as a courtesy car, or just bought. Two cars on one drive, one petrol, one diesel. A well-known forecourt with the pumps in a different order. Fuelling up in a hurry on the way to Hatfield & Stainforth, with a train to catch. The first fill-up in a diesel Renault Megane after years of driving petrol is precisely the moment it happens. Your hand repeats what it has always done when you add rain, a phone call or a back seat full of children.
How to avoid petrol in a diesel on your next fill-up in The Lings
- The label is what matters, and so read the pump instead of the colour: in the UK unleaded handles are normally green and diesel black, yet not on each forecourt.
- Check the filler flap. Many cars state the fuel inside the flap or on the cap. Look at it on your first fill in a car you do not know.
- A coloured fob or a sticker on the diesel's key does more than any amount of intending to remember, in a home with one of each.
- It sounds daft and it does the trick: 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 simple to make whilst your mind is on something else, and so your phone goes away.
- Some diesels come with a filler built to block a petrol nozzle, and devices you can add are available for motors without one. Such an inhibitor helps up to a point — as a safety net, not a reason to stop reading the petrol pump.
- Stop the moment you realise. Less petrol in that tank means a thinner mix. It doesn't change what to do next, which is still not to fire it up.
Petrol already in a diesel around The Lings? Start here
Short and simple, then, is the order of things. Starting it is out, and so is switching on your ignition. If you are still on the forecourt — the nearest petrol station or anywhere else — ask the staff to help you push it away from the pump. Next, 0333 366 0103. We will ask what got in, about how much, and if it's been run.
Corrosion and deposits are the issue with AdBlue, where petrol brings lost lubrication. So if it was AdBlue, say so — and see its own The Lings page.
One petrol in a diesel task in The Lings costs more than another. Why?
There's no fair single quote for this, because the four situations above are four separate tasks. What moves your cost is chiefly which of them you are in. Where your car is matters too, and whether a technician can safely reach it, after the share of petrol to what your tank takes.
Three queries come first, before any quote, instead of after — what was put in, how much, has it run — and that is the reason. With those answers, you get a straight figure instead of a range.
About The Lings itself
The Lings is a suburban area located near Doncaster in South Yorkshire, situated at a low elevation of around 9 metres above sea level. The Lings is characterized by its predominantly semi-detached housing stock, reflecting the typical residential development patterns of the region. The Lings sits within a network of similar suburban areas, including nearby Dunscroft, Hatfield, and West End, and is approximately 6 miles from the centre of Doncaster. The Lings is also relatively distant from London, at around 147 miles away.
Across South Yorkshire and around The Lings: fuel drain cover
Our vans answering petrol in diesel call-outs in The Lings, in the DN postcode area, equally work the locations near it, Dunscroft, Hatfield and West End included. The car does not need to move to us: our technicians drain on a forecourt, in a supermarket car park, in a lay-by or on your own driveway.
At the petrol pump around The Lings, right now?
The best spot there is, then — that's where you are. Leave the car switched off, then ring.