Should You Worry? Petrol in a Diesel Car in St Aethans
Unstarted? Then less worried than you likely feel. "Have I wrecked it?" is the first thing anyone around St Aethans asks, and the truthful answer is usually no, since petrol left in a diesel tank harms nothing until it is dragged through the fuel system — by ignition priming, by your starter, or by driving. Keep it that way: leave the motor off then ring Petrol in Diesel. Below, you will find what petrol actually does inside a diesel, how far it might have gone, and how to stop it happening to you a second time.
What petrol in a diesel does to the motor
Two jobs fall to diesel on its journey round a motor. It lubricates to begin with, and only then does it burn. Extremely fine clearances go into your injectors and the high-pressure fuel pump, and only your diesel flowing through stops those surfaces grinding together.
Petrol does the first job badly and the second not at all. A pump running on a petrol blend is wearing itself out, because petrol is thinner than diesel and strips out the lubrication your fuel system relies on. Petrol is also made to resist igniting under compression — the opposite of what a diesel wants from its fuel — and that's where the rattling comes.
The shape of the issue is clear when you put those together. Contact does not do the harm — circulation does. Where the petrol is only in the tank, it is a problem of fuel, nothing more. Whatever a worn pump sheds goes on, borne by the fuel, into the injectors further along, which is why a pump that has worked on that petrol is where a mechanical problem begins.
How bad is petrol in a diesel? Four situations our technicians see around St Aethans
The best case there can be: filled up, never started. That petrol is inside your tank and only that tank, and the job is a drain and a flush where the vehicle sits. This is the one scenario that can only really occur at a forecourt, as anywhere else the vehicle has been driven to get there.
Started for a second, or only your ignition on. Your system has been primed, so petrol has left your tank and reached your filter and the fuel lines. That is generally still an easy task — a drain, a flush, and your filter seen to.
Those few miles driven were your pump running on fuel thinned by petrol throughout. Tank, lines, filter, then fresh fuel run through the entire circuit: that is the work, and the way the vehicle was driven matters as much as the distance. On the school run to the local primary school, the distance is small. Any mileage on the M90, over 50 miles from St Aethans, means the motor working hard throughout, and a run to Inverness, under 50 miles away, is a very different task as well.
It complained, and only then stopped: smoke, rattling, a throttle gone soft, an idle gone uneven. That is the engine telling you its fuel no longer is acting like diesel. Stop on the spot — on the verge on Headland Rise, at the kerb, down a side road — and don't move it. What comes first is still the fuel drain and flush, and that sorts it out, with permanent damage very unusual if a vehicle is stopped quickly.
St Aethans drivers and that petrol in a diesel stories they hear
Myth: "Fill it the rest of the way with diesel and it'll be fine." It will not. Nothing is removed by topping up — you are left with a bigger tank, still the same mix. A diesel fuel system does not accept petrol by percentage in the way that guidance supposes.
"Current diesels can handle a little petrol" — a myth, and nearer the opposite. At higher pressure, through smaller parts: that's how a modern diesel moves its fuel, and so the protection matters more, not less.
Myth: "If it starts and drives, there is no damage done." This is the one that catches motorists. Feed diesel to a petrol engine and it usually will not run, and so the driver stops — and the damage stops with them. A diesel fed petrol usually starts, idles and drives away as though nothing has happened, while the pump wears. Being able to run isn't the same as being fine.
An old workaround for a different problem lies behind this one. Myth: "Add some two-stroke oil and drive the car home." That petrol is still in your tank afterwards, and what it has diluted isn't put back.
The next start sends petrol back round your pump out of your lines and the fuel filter, where some of that sits after your engine has run. That is why draining your tank yourself does not sort it — a myth. Draining petrol into a can at the roadside is also genuinely hazardous.
How it happens: petrol in a diesel
Nobody does it on purpose, and it is rarely carelessness. The forecourt makes it easy: the petrol nozzle is the slimmer of the two, and it slides into a diesel filler with almost no resistance, whilst a diesel nozzle generally will not go into a petrol vehicle at all. So the slip runs one way.
The moment routine stops matching the car is the moment it happens. Hire cars, courtesy cars, and cars that are new to you. Two motors on one driveway, one petrol, one diesel. Your normal forecourt, its pumps now in a different order. Rushing for a train outside Elgin and fuelling up en route. A new-to-you diesel Renault Megane, 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.
How to prevent petrol in a diesel on your next fill-up around St Aethans
- Read the petrol pump, not the colour. In the UK unleaded handles are usually green and diesel black, yet not on each forecourt. The label is what counts.
- Plenty of cars state the fuel inside your filler flap or on the cap, so check there on your first fill in a motor you do not know.
- One of each in the household? Mark your key to the diesel — a bright fob, a sticker — since intending to remember isn't enough.
- It sounds silly and it works: on the first fill in a new or hired car, say "diesel" aloud before you take the nozzle off the petrol pump.
- Mistakes like this are easy to make while your mind is on something else, so your phone goes away.
- Up to a point, a misfuel inhibitor helps: some diesels have a filler designed to refuse a petrol nozzle, and add-on devices exist for the remainder. Treat it as a backstop, and keep reading the petrol pump.
- Noticing it mid-fill? Stop at once. A weaker mix results from less petrol in the tank, yet the next stage stays the same: do not fire it up.
St Aethans: already put petrol in a diesel?
The order of things is brief, then. Leave it unstarted, with your ignition off too. Ask the attendants to help you push it away from the pump if you are still on the forecourt, whether that is the nearest petrol station or somewhere else. Then phone 0333 366 0103 and tell us what went in, about how much, and whether it has run.
Corrosion and deposits form the trouble with AdBlue, where petrol means lost lubrication. So if it was AdBlue, say so — and read its own St Aethans page.
What makes one St Aethans petrol in a diesel task cost more than the next
Four different jobs sit behind the four scenarios above — which is why there's no honest single price. Mostly, your cost shifts with which situation you're in. Two things follow that: the petrol that got in as a proportion of what that tank takes, then the place your car is in and whether a van can get to it safely.
Before any quote, not after, we ask three queries: your fuel that was put in, its amount, and whether it has run. That's why. Given those answers, there is a straight figure rather than a range.
About St Aethans and its setting
St Aethans is a coastal suburban area in Moray, situated near the towns of Burghead and Cummingston, with St Aethans itself lying at an elevation of 32 metres. St Aethans is characterised by its predominantly detached housing stock, reflecting the area's residential nature. St Aethans is located within commuting distance of Inverness, the nearest city, and St Aethans benefits from its proximity to the scenic Moray coastline.
Fuel drain cover across Moray, St Aethans included
Petrol in diesel jobs in St Aethans — part of the IV postcode area — go to teams that likewise cover the locations round it, Burghead, Cummingston and Charlestown included. You need not move your car to us. Forecourts, supermarket car parks, lay-bys and your own drive are all spots where we work.
At the pump around St Aethans, right now?
Then, you couldn't be in a better spot. Phone, and keep it turned off.