West Barns: Petrol in a Diesel Car? How Worried to Be
Likely less than you are now — as long as no one has started it. "Have I wrecked it?" is the first thing everyone around West Barns asks, and the honest answer is generally no, since petrol left in a diesel tank harms nothing until it is dragged through your fuel system — by ignition priming, by the starter, or by being driven. Leave your engine off then ring Petrol in Diesel — that keeps it like that. What petrol really does to a diesel, how to gauge how far it has travelled, and how to stop it from happening again: that is the rest of this page.
The motor and petrol in a diesel: what goes on
Passing through a motor, diesel does two things at once. It lubricates to begin with, and only then does it burn. Very fine gaps are built into the fuel injectors and the high-pressure fuel pump, and just the diesel flowing through stops their surfaces grinding together.
The second task petrol doesn't do at all, and the first it does badly. It's runnier than diesel and removes the protection the system hinges on, and so a pump running on a petrol mixture is a pump wearing itself. And petrol is designed to resist igniting under compression, which is the opposite of what a diesel needs from its fuel. That's where the knocking comes from.
Put those together and the shape of the trouble is clear. It's movement that does the damage, not contact. Where the petrol is only in your tank, it's a problem of fuel, nothing more. Whatever a worn pump sheds travels on, carried by your fuel, into the fuel injectors further along, which is why a pump that has been working on that petrol is where a mechanical issue starts.
How bad is petrol in a diesel? Four scenarios our technicians see in West Barns
The best case there is: filled up, not once started. Being at a forecourt is what makes this the case: elsewhere, the car has been driven there to begin with. With that petrol held inside your tank alone, it is cleared and purged on the spot, and nothing more is needed.
The ignition switched on, or a short start. Petrol has come out of that tank and got to the filter and the lines, because the system has been bled. Drain, flush, see to the fuel filter: still normally straightforward.
Those few miles on the road were the pump working on fuel weakened by petrol the whole way. Tank, lines, filter, then fresh fuel run through the whole system: that's the work, and the way the car was driven counts as much as the miles. On the school run to the local primary school, the mileage is small. A run as far as Edinburgh, under 25 miles away, is a very different job. So is any mileage on the M8, under 50 miles from West Barns, where the motor has been labouring hard the whole time.
Driven till it complained. Knocking, a ragged idle, smoke, a throttle that has gone soft. What you are hearing is your engine reporting fuel that no longer runs like diesel. Leave it wherever it stops: a lay-by, a quiet street, the verge on Edinburgh Road. What goes first is still the fuel drain and flush-through, and that sorts it out, with permanent damage very rare when a car is pulled over quickly.
What West Barns drivers get told about petrol in a diesel — and the stories in it
Myth: topping up to full with diesel makes it fine. It does not. Nothing is removed by topping up — you are left with a bigger tank, still the same mix. The idea behind that guidance — that diesel fuel systems tolerate petrol by percentage — is wrong.
If anything, the opposite is true. Myth: "A current diesel can cope with a bit of petrol." At higher pressure, through more precise components: that's how a newer diesel moves its fuel, and so the lubrication counts more, not less.
Myth: "If it starts and drives, there's no harm done." This is the one that fools people. Feed diesel to a petrol motor and it usually 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. Fine and running aren't the same at all.
Myth: "Add some two-stroke oil and drive it home." It's an outdated workaround for a separate issue. None of what petrol diluted is put back by it — and afterwards, that tank still contains the petrol.
Myth: "Drain the tank yourself and you're sorted." After the engine has been run, some of the petrol is no longer inside your tank: it is in the filter and your lines, and it goes straight back through the pump on your next start. And, a can of petrol filled by the roadside is truly dangerous.
How it happens: petrol in a diesel
On purpose? Never. Through carelessness? Seldom, if ever. A diesel nozzle mostly won't fit a petrol car, yet the narrower petrol nozzle goes into the filler of a diesel almost without resistance — so forecourts make this one error easy, and just in one direction.
It occurs when routine and the vehicle stop matching. A new vehicle, a hire car or a courtesy car. Households running one of each, petrol and diesel. Your normal forecourt, its pumps now in a different order. A train to catch, and a rushed fill on the way to Dunbar. Years of petrol vehicles behind you, a diesel Renault Megane in front of you at the forecourt for its first tank — that's when. Add a back seat full of kids, a phone call or rain, and the hand takes over.
Next time you fill up around West Barns: preventing petrol in a diesel
- Green for unleaded and black for diesel is usual in the UK — yet not on each forecourt. Go by the label on the pump, not the colour.
- In a vehicle you do not know, look inside the flap over the filler or at the cap before the first fill: many vehicles state the fuel type there.
- Mark the key. In a household with one of each, a coloured fob or a sticker on the diesel's key does more than any amount of intending to remember.
- It seems silly and it does the trick: on your first fill in a new or hired car, say "diesel" aloud before you lift the nozzle off the petrol pump.
- Thinking about something else is when this becomes an easy mistake to make, and so tuck the phone away and keep your mind on the pump.
- Up to a point, a misfuel inhibitor helps: some diesels come with a filler designed to refuse a petrol nozzle, and aftermarket devices exist for the rest. Treat it as a backstop, and keep checking the pump.
- Spotting it mid-fill? Stop there and then. A thinner blend results from less petrol in your tank, but the next stage stays the same: don't start it.
West Barns: already put petrol in a diesel?
The order of things is brief, then. Do not turn your ignition on, and don't fire it up. If you're still at the forecourt — JET or anywhere else — ask the staff to help you roll the car clear of the pump. Then phone 0333 366 0103 and tell us what was put in, about how much, and if it has run.
AdBlue, not petrol? Then say so. Corrosion and deposits, not lost lubrication, make it a separate fault — West Barns has a page just for it.
One petrol in a diesel job in West Barns costs more than another. Why?
The four scenarios above are four separate tasks, so no single quote for this would be fair. Mostly, the cost shifts with which one you're in. Where the vehicle is counts too, and whether our van can safely get to it, after the share of petrol to what the tank holds.
Three questions come first, before any quote, instead of after — what got in, how much, has it run — and that is the reason. Those replies are what turn a range into one firm number.
About West Barns, briefly
West Barns is a small coastal village in East Lothian, situated near the towns of Dunbar and the beaches of Belhaven. West Barns lies at a low elevation of around 10 metres, close to the North Sea coast and within commuting distance of Edinburgh. West Barns has a mix of housing types, but semi-detached homes are particularly common in the village. West Barns is also near other small settlements like Bielside and Winterfield Mains.
Across East Lothian and around West Barns: fuel drain cover
Bielside, Winterfield Mains and Belhaven are among the spots near West Barns that the same vans work, answering petrol in diesel jobs across West Barns's EH postcode area. No need to move your car to us. Forecourts, supermarket car parks, lay-bys and your own drive are all spots where we work.
West Barns: still at the petrol pump?
The best spot there is, then — that is where you are. Leave it turned off, and ring.