Should You Worry? Petrol in a Diesel Car in Mynydd-bach
Probably less than you already are — provided nobody has started the vehicle. Everyone in Mynydd-bach starts with "have I wrecked it?", and the honest answer is generally no: petrol left inside that tank of a diesel remains harmless until priming, cranking or driving pulls it into the fuel system. Petrol in Diesel is who to phone, with the engine left off, so it remains that way. What petrol really does to a diesel, how to judge how far it has gone, and how to stop it from happening a second time: that's the remainder of this page.
Inside your engine: what petrol in a diesel really does
Two jobs fall to diesel on its journey round a motor. It ignites, and before it burns it protects. What keeps the surfaces inside your high-pressure pump and the fuel injectors from grinding against each other is the diesel passing through them — they are built to very fine clearances.
Petrol does the first job poorly and the second not at all. A pump running on a petrol blend is wearing itself out, since petrol is thinner than diesel and takes away the protection the fuel system depends on. Petrol is also made to resist igniting under compression — the opposite of what a diesel needs from its fuel — and that is where any clattering starts.
Taken together, they show what shape the issue has. The damage is done by movement, not by contact. Where the petrol is only in your tank, it is an issue of fuel, nothing more. 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 that petrol is where a mechanical fault starts.
How serious is petrol in a diesel? Four scenarios we see around Mynydd-bach
The best case there is: filled up, never started. On a forecourt, and truly only there, the petrol is still confined to the tank — because everywhere else the vehicle was driven to get to it. The task is emptying and flushing on the spot.
Your ignition turned on, or a short start. Petrol has left your tank and got to the filter and the lines, since the fuel system has been bled. That is generally still an easy job — a drain, a flush, and the filter dealt with.
Your pump has worked a few miles on weakened fuel — that is what driving it does. Mileage is only half of that; how hard it was driven matters equally. Either way the work includes your tank, your lines, the fuel filter and clean fuel through the entire system. A school run to the local primary school is one thing. Getting as far as Swansea, under 3 miles away, makes a very different task — as does any distance on the M4, under a mile from Mynydd-bach, with the engine working hard all the way.
It protested, and only then stopped: smoke, rattling, a throttle gone soft, an idle gone uneven. What you are hearing is the motor reporting fuel that no longer acts like diesel. Whether it's the verge on Tirdeunaw Close, a lay-by or a side street, stop there then leave it. The drain and flush still come first, and they take care of it: if a vehicle is stopped soon, permanent damage is very uncommon.
Petrol in a diesel stories Mynydd-bach motorists hear
It will not be fine. The myth: "Fill it the rest of the way with diesel and it'll be." A fuller tank of the same mixture is all you get, since topping up takes out nothing. Percentage isn't how a diesel fuel system tolerates petrol, whatever that advice supposes.
"Newer diesels can handle a little petrol" — a myth, and closer to the opposite. Finer components and higher pressure are the way a modern diesel runs its fuel, and that makes the lubrication count more, not less.
"It starts, it drives, and so no harm done" — the myth that catches more motorists than any other. The driver of a petrol engine fed diesel usually has no choice but to stop, since it will not run, and the harm stops with them. A diesel fed petrol generally starts, ticks over and drives away as though nothing has happened, while your pump grinds. Fine and running are not the same thing.
Myth: "Add some two-stroke oil and drive it home." It's an outdated workaround for a different fault. It doesn't put back what petrol has diluted, and the petrol is still in that tank later.
The next start sends petrol back round the pump from your lines and your filter, where some of it ends up after the motor has been run. That's why draining the tank yourself doesn't leave you sorted — a myth. Also, a can of petrol filled by the roadside is truly risky.
Petrol in a diesel: how does it happen?
On purpose? Never. Through carelessness? Rarely, if ever. A diesel nozzle generally will not fit a petrol motor, but the slimmer petrol nozzle goes into the filler of a diesel almost without resistance — so forecourts make this one error easy, and only in that direction.
The moment routine stops matching the vehicle is the moment it occurs. Courtesy car, hire car, or a car that's brand new. Households running one of each, petrol and diesel. A forecourt you know, only with its pumps laid out differently. A hurried fill en route to Llansamlet with a train to catch. Years of petrol motors behind you, a diesel Volkswagen Passat in front of you at the forecourt for its first tank — that's when. Throw in rain, a phone call or a back seat full of children, and your hand repeats what it has always done.
Next time you fill up around Mynydd-bach: preventing petrol in a diesel
- A green handle 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.
- Plenty of motors state the fuel inside the filler flap or on the cap, so check there on your first fill in a car you do not know.
- Good intentions count for less than a sticker or a fob in a bright colour on your diesel's key when a house has one of each. So label it.
- It seems silly and it does the trick: on your first fill in a new or hired car, say "diesel" out loud before you lift the nozzle off the pump.
- Thinking about something else is when this becomes an easy mistake to make, and so put the phone away then keep your mind on the pump.
- Add-on devices exist for cars without one, and some diesels come with a filler that won't accept a petrol nozzle. Useful — but a backstop only, never a reason to stop checking the label.
- As soon as you realise, stop: less petrol inside that tank means a thinner blend. What to do next doesn't change, though — still don't crank it.
Put petrol in a diesel in Mynydd-bach already?
Then the order of things is short. Leave it unstarted, with your ignition switched off too. Ask the attendants to help you push it away from the petrol pump if you're still on the forecourt, whether that is Texaco or somewhere else. Then ring 0333 366 0103 and tell us what was put in, about how much, and if it's run.
If it was AdBlue instead of petrol, say so. That is a different problem — corrosion and deposits and not lost protection — and it has its own page for Mynydd-bach.
Why one petrol in a diesel job in Mynydd-bach costs more than another
There is no honest single quote for this, because the four situations above are four separate tasks. What shifts your cost is chiefly which of them you're in. Two things come after that: the petrol that got in as a proportion of what that tank takes, then the spot the vehicle is in and whether a van can get to it safely.
Before any quote, not after, we ask three queries: the fuel that got in, its quantity, and if it has run. That's why. A range turns into a straight figure when those replies are in.
About Mynydd-bach itself
Mynydd-bach is a suburban area located inland, approximately 2.9 miles from Swansea city centre, and sits at an elevation of around 148 metres. Mynydd-bach is characterized by its semi-detached housing stock, which is typical of many suburban areas in south Wales. Mynydd-bach is close to nearby places such as Tirdeunaw, Mynydd-Garn-Lwyd, and Clase, and is home to a population of around 3613 people.
Mynydd-bach and Swansea: where our fuel drain cover runs
Petrol in diesel jobs in Mynydd-bach — part of the SA postcode area — go to vans that also cover the locations around it, Tirdeunaw, Mynydd-Garn-Lwyd and Clase included. Our engineers drain wherever the car is — your own driveway, a lay-by, a supermarket car park, a forecourt — so it never needs to come to us.
In Mynydd-bach and still at the petrol pump?
The best spot there is, then — that is where you are. Keep it off. Ring.