How Worried Should You Be? Petrol in a Diesel Car in Wembdon
Probably less than you are now — as long as nobody has started the car. Petrol resting in a diesel tank does nothing to your engine until something draws it through your fuel system — your ignition priming your pump, your starter, or the drive on its own. So the truthful answer to the first question anyone in Wembdon asks, "have I wrecked it?", is normally no. To keep the car like that, call Petrol in Diesel then leave the engine alone. Further down, you will find what petrol really does inside a diesel, how far it may have gone, and how to stop it happening to you again.
The motor and petrol in a diesel: what goes on
Two tasks fall to diesel on its journey through a motor. It combusts, and before it combusts it lubricates. What keeps the surfaces inside the high-pressure pump and the fuel injectors from wearing down against one another is your diesel flowing through them — they are designed to very fine gaps.
The second job petrol doesn't do at all, and the first it does badly. It's runnier than diesel and takes away the lubrication the system rests on, and so a pump running on a petrol mixture is a pump wearing itself. And petrol is made to resist igniting under compression, which is the reverse of what a diesel needs from its fuel. That is where the clattering comes from.
Combined, those leave the shape of the problem clear. Contact doesn't do the damage — movement does. A tank with petrol in it is a fuel problem. Whatever a worn pump sheds travels on, borne by your fuel, into the fuel injectors downstream, which is why a pump that has been working on the petrol is where a mechanical fault starts.
How serious is petrol in a diesel? Four scenarios our engineers see in Wembdon
Fuelled, and never started: no case is better. 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 that tank alone, it's drained and flushed right where it stands, and nothing more is needed.
Started for a moment, or only your ignition on. Petrol has left that tank and got to the filter and the fuel lines, because the system has been primed. Still usually straightforward: drain, flush, and the filter seen to.
A few miles driven, and your pump has spent each of them working on thinned fuel. How hard the vehicle was driven counts as much as how far, and the work covers your tank, the lines, your filter and clean fuel through the whole circuit. On the school run to Wembdon St George's Church School, the distance is small. Any mileage on the M5, under 3 miles from Wembdon, means the motor has worked hard throughout, and a run to Wells, under 25 miles away, is a very different task as well.
It protested, and only then stopped: smoke, clattering, a throttle gone soft, an idle gone lumpy. The engine is telling you your fuel is no longer acting like diesel. Stop on the spot — on the verge on Wembdon Rise, at the kerb, down a side road — and do not move it. The drain and flush still come first, and they take care of it: when a vehicle is stopped soon, permanent damage is very uncommon.
Wembdon motorists and the petrol in a diesel stories they hear
Myth: "Fill it the rest of the way with diesel and it will be fine." It will not. Topping up removes nothing; it gives you a fuller tank of the same mixture. The idea behind that guidance — that diesel fuel systems accept petrol by percentage — is wrong.
Myth: "A current diesel can cope with a bit of petrol." If anything, the reverse. Lubrication matters more on newer diesels, not less, since their fuel runs through more precise components at higher pressure.
Myth: "If it starts and drives, there's no damage done." This is the one that fools people. Diesel in a petrol motor normally means a motor that will not run: the motorist stops, and so does the harm. Nothing seems to have happened when a diesel fed petrol fires up, ticks over and drives away, as it usually does; meanwhile your pump wears. Fine and running are not the same at all.
Myth: "Add some two-stroke oil and drive the car home." It's an old workaround for a separate fault. It doesn't put back what petrol has weakened, and the petrol is still in the tank later on.
The next start sends petrol back round the pump out of your lines and the fuel filter, where some of it ends up after the motor has run. That's why draining your tank yourself doesn't sort it — a myth. Draining petrol into a can at the roadside is also really hazardous.
How it happens: petrol in a diesel
It's rarely carelessness, and nobody does it on purpose. A diesel nozzle mostly will not fit a petrol vehicle, but the slimmer petrol nozzle goes into the filler of a diesel almost without resistance — so forecourts make this one mistake straightforward, and just in that direction.
Habit and your car falling out of step is how it happens. Courtesy car, hire car, or a motor that's new. One petrol and one diesel on the driveway of the same household. The pumps in a different order on a well-known forecourt. A hurried fill en route to Bridgwater with a train to catch. Years of petrol vehicles behind you, a diesel Volkswagen Golf in front of you on the forecourt for its first tank — that's when. Add rain, a phone call or a back seat full of children, and your hand does what it has always done.
How to prevent petrol in a diesel at your next fill-up around Wembdon
- Not every forecourt in the UK follows green for unleaded and black for diesel, though most usually do. Check the petrol pump's label; the colour is just a clue.
- In a vehicle you don't know, look inside the flap over the filler or at the cap before your first fill: plenty of vehicles print the fuel type there.
- One of each in the household? Label your key to the diesel — a bright fob, a sticker — since meaning to remember isn't enough.
- Before the nozzle comes off the petrol pump the first time you fuel a hired or new vehicle, say "diesel" aloud. Daft, perhaps, yet it does the trick.
- Thinking about something else is when this becomes an easy mistake to make, and so tuck your phone away and keep your mind on the petrol pump.
- Up to a point, a misfuel inhibitor helps: some diesels come with a filler designed to refuse a petrol nozzle, and aftermarket devices are available for the remainder. Count it as a backstop, and keep checking the pump.
- As soon as you realise, stop: less petrol in the tank means a weaker mix. What to do next doesn't change, though — still do not start it.
Put petrol in a diesel in Wembdon already?
Then the order of things is short. Starting it is out, and so is switching on your ignition. Ask the staff to help you push it clear of the petrol pump if you are still on the forecourt, whether that's Shell or anywhere else. Ring 0333 366 0103 next, with three facts — your fuel, the approximate quantity, and whether it has run.
If it was AdBlue rather than petrol, say so. That's a different issue — corrosion and deposits instead of lost lubrication — and it has its own page for Wembdon.
Why one petrol in a diesel job around Wembdon costs more than another
The four scenarios above are four separate jobs, so no single price for this would be fair. What moves the cost is chiefly which of them you're in. The proportion matters next, meaning how much of that tank is petrol, and then the location of the car and whether getting to it is safe for our van.
What got in, how much, and whether it's run — three queries our engineers ask before pricing, not after, for precisely that reason. Those answers turn a range into a straight figure.
About Wembdon
Wembdon is a village situated on the River Parrett in Somerset, with a low elevation of around 13 metres above sea level. Wembdon lies near the towns of Bridgwater and Wells, and is surrounded by other small settlements such as Newtown and Northfield. Wembdon has a population of approximately 1555 people, and its housing stock is predominantly made up of detached homes. Wembdon is located in the South West region of England, about 127.7 miles west of London.
Wembdon and Somerset: where our fuel drain cover runs
Petrol in diesel calls in Wembdon — part of the TA postcode area — go to teams that likewise cover the spots around it, Newtown, Northfield and Bridgwater among them. The vehicle does not need to come to us: our technicians drain at a forecourt, in a supermarket car park, in a lay-by or on your own driveway.
In Wembdon and still at the petrol pump?
Then you're in the best place there is. Call, and keep it switched off.