Tircoed: Petrol in a Diesel Car? How Worried to Be
Less than you likely are, if it hasn't been started. "Have I ruined it?" is the first thing everyone in Tircoed asks, and the honest answer is usually no, because petrol resting in a diesel tank harms nothing until it's dragged through your fuel system — by ignition priming, by your starter, or by driving. To leave it that way, ring Petrol in Diesel then leave the motor alone. Further down, this page sets out what petrol actually does inside a diesel, how far it may have gone, and how to stop it happening to you again.
What petrol in a diesel does to the motor
On its way through a motor, diesel does two jobs. Oiling comes before burning; it does both. Designed to extremely fine tolerances, the injectors and the pump depend on your diesel flowing through them to stop their surfaces wearing against one another.
Of these two tasks, petrol manages the first badly and the second never. Being less viscous than diesel, petrol strips away the lubrication a fuel system needs, leaving a pump running on the mixture wearing itself. It is equally made to resist igniting under compression — the opposite of what a diesel needs — which is why you get the knocking.
Taken together, they make clear the shape the problem takes. The harm is done by circulation, not by contact. Any tank with petrol in it is a fuel problem. The start of a mechanical one is a pump that has been working on that petrol — and whatever a worn pump sheds moves on with the fuel to the injectors beyond it.
How serious is petrol in a diesel? Four situations our engineers see around Tircoed
Fuelled, and never started: nothing beats it. On a forecourt, and truly only there, the petrol is still limited to your tank — because everywhere else the car was driven to reach it. The job is emptying and cleaning on the spot.
Started for a second, or just the ignition on. With your system primed, your lines and filter now hold petrol that has come from that tank. Drain, flush, deal with your filter: still usually straightforward.
Your pump now spent a couple of miles on diluted fuel — that's what driving it does. Tank, lines, filter, then clean fuel run through the entire circuit: that's this work, and the way the vehicle was driven matters as much as the mileage. Driving the children to the local primary school is one sort of trip. Getting as far as Swansea, under 5 miles away, makes a very different task — as does any mileage on the M4, under a mile from Tircoed, with the engine working hard the whole time.
Driven on until it complained — rattling, smoke, a ragged idle, a dead throttle. That's the engine telling you its fuel has stopped acting like diesel. Whether it is the verge on Heol Tircoed, a lay-by or a side road, stop where you are then leave it. What comes first is still the drain and flush-through, and that deals with it, with long-term damage very unusual if a vehicle is pulled over quickly.
Myths Tircoed people hear about petrol in a diesel
"Top it up the rest of the way with diesel and it will be fine" — a myth. It will not. Nothing comes out when you top up — that tank just holds more of the same mixture. The idea behind that advice — that diesel fuel systems accept petrol by percentage — is wrong.
Myth: "A modern diesel can cope with a bit of petrol." If anything, the opposite. More precise parts and higher pressure are the way a current diesel runs its fuel, and that makes the lubrication matter more, not less.
"It starts, it drives, so no harm done" — the myth that catches more motorists than any other. A petrol engine fed diesel normally won't run, and so the driver stops and the harm stops with them. Nothing looks to have happened when a diesel fed petrol fires up, ticks over and drives away, as it usually does; meanwhile your pump grinds. Fine and running aren't the same thing.
Not so: a two-stroke additive lets you to drive home. It is an old fix, supposed for another issue. That petrol is still inside your tank after that, and what it has diluted isn't put back.
Myth: "Drain the tank yourself and you are sorted." After the engine has been run, some of that petrol is no longer in your tank: it is in the fuel filter and your lines, and it goes right back through your pump on your next start. On top of that, petrol drained into a can by the road is genuinely hazardous.
Petrol in a diesel: how does it take place?
On purpose? Never. Through carelessness? Rarely, if ever. The petrol nozzle is the slimmer of the two and slides into a diesel filler with almost no resistance; a diesel nozzle mostly won't go into a petrol motor at all. The forecourt makes it simple, and the error runs one way.
It occurs when habit and your car stop matching. Courtesy car, hire car, or a vehicle that's brand new. A household with one petrol and one diesel on the driveway. A familiar forecourt with the pumps in a different order. Racing for a train outside Gowerton and filling up en route. Precisely the moment it takes place: after years of driving petrol, someone fills a diesel Volkswagen Passat for the first time. With rain, a call coming in, or children to deal with, the hand simply does what it has always done.
How to avoid petrol in a diesel on your next fill-up around Tircoed
- The label is what counts, so read the petrol pump instead of the colour: in the UK unleaded handles are usually green and diesel black, yet not on every forecourt.
- Many motors state the fuel type inside your filler flap or on the cap, and so check there on the first fill in a car you do not know.
- A coloured fob or a sticker on the diesel's key achieves more than any amount of meaning to remember, for a house with one of each.
- 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 straightforward to make whilst your mind is on something else, and 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 rest. Treat it as a backstop, and keep reading the pump.
- Stop the moment you realise. Less petrol inside the tank makes a thinner mix. It does not change what to do next, which is still not to fire it up.
Tircoed: already put petrol in a diesel?
Short and simple, then, is the order of things. Starting it is out, and so is turning on your ignition. 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 anywhere else. Next, 0333 366 0103. We'll ask what went in, about how much, and if it's been run.
If it was AdBlue instead of petrol, say so. That's a different fault — corrosion and deposits and not lost protection — and it has its own page for Tircoed.
One petrol in a diesel task around Tircoed costs more than another. Why?
The four scenarios above are four different jobs, so no single price for this would be fair. Which of them you are in is mostly what moves your cost. Beyond that it is the ratio — how much petrol went in against how much the tank takes — and after that where your car is and whether a technician can reach it safely.
That's why our technicians ask three queries before costing rather than after: what went in, how much, and whether it has run. With those replies, there is a straight figure instead of a range.
About Tircoed itself
Tircoed is a village situated on the banks of a river in Swansea, with a relatively low elevation of 64 metres. Tircoed lies close to the nearby villages of Penllergaer and Pontlliw, and is approximately 4.9 miles from the city of Swansea. Tircoed has a population of around 1145 people, predominantly living in detached houses. Tircoed is located in a scenic area, with Bach-y-gwreiddyn nearby.
Tircoed and Swansea: where our fuel drain cover reaches
Tircoed sits in the SA postcode area, and our teams that answer petrol in diesel call-outs there work the spots around it as well — Penllergaer, Bach-y-gwreiddyn and Pontlliw among them. The car doesn't need to move to us: our technicians drain at a forecourt, in a supermarket car park, in a lay-by or on your own driveway.
In Tircoed and still at the pump?
Nothing beats it: that is where you now are. Switched off it stays; then phone.