How Worried Should You Be? Petrol in a Diesel Car in Kidwelly
Probably less than you already are — provided nobody has started the vehicle. Till your ignition primes your pump, the starter turns, or the car is driven, petrol in a diesel tank just waits there and does no harm. Which makes the truthful reply to that first Kidwelly question — "have I ruined it?" — normally no. To leave the car like that, call Petrol in Diesel and leave your motor alone. Below, this page sets out what petrol really does inside a diesel, how far it may have got, and how to stop it happening to you a second time.
Petrol in a diesel: what does it do to your engine?
Diesel has two jobs on its way through a motor. It lubricates first, and only then does it burn. Extremely fine gaps are built into your injectors and the high-pressure pump, and only your diesel running through stops their surfaces grinding together.
Poorly at the first, not at all at the second: that is petrol. Being less viscous than diesel, petrol strips out the lubrication a fuel system needs, leaving a pump on that mixture to wear itself. It is also made to resist igniting under compression — the opposite of what a diesel needs — which is where you get the clattering.
Put those together and the shape of the trouble is clear. The harm is done by movement, not by contact. Petrol in a tank is a fuel issue. A pump that has been working on that petrol is the beginning of a mechanical one, and whatever a worn pump sheds travels on with your fuel to the injectors further on.
How serious is petrol in a diesel? Four situations our technicians see in Kidwelly
Fuelled but not once started — the best it gets. 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 the tank alone, it's emptied and rinsed right where it stands, and nothing more is needed.
Started for a moment, or only your ignition on. Petrol has left that tank and reached the fuel filter and the lines, since the fuel system has been primed. Usually nothing more than draining, flushing and sorting your filter, and so still simple.
Driven a couple of miles. Now the pump has spent those miles running on thinned fuel. Tank, lines, filter, then fresh fuel run through the entire circuit: that's this work, and the way the car was driven matters as much as the miles. Short trips, like the school run to the local primary school, are one matter. Any distance on the M4, under 15 miles from Kidwelly, means the motor working hard throughout, and a run to Swansea, under 25 miles away, is a very different task too.
Driven on till it complained — rattling, smoke, a lumpy idle, a dead throttle. The engine is telling you the fuel is no longer behaving like diesel. Stop on the spot — on the verge on Lady Street, at the kerb, down a side road — and don't move it. A vehicle pulled over quickly very rarely has permanent damage, as the drain and the flush, which still come first, take care of it.
Kidwelly drivers and the petrol in a diesel myths they hear
It will not be fine. The myth: "Fill it the rest of the way with diesel and it'll be." Topping up takes out nothing; it gives you a bigger tank of the same mixture. Percentage isn't how a diesel fuel system copes with petrol, whatever that guidance supposes.
If anything, the opposite is true. Myth: "A newer diesel can cope with a bit of petrol." Lubrication matters more on modern diesels, not less, since their fuel passes through finer parts at higher pressure.
This is the one that catches motorists. Myth: "If it starts and drives, there's no damage done." Any petrol engine fed diesel generally won't run, and so the motorist stops and the damage stops with them. Nothing seems to have happened when a diesel fed petrol fires up, ticks over and drives away, which it usually does; meanwhile the pump wears. Running isn't the same as fine.
Myth: "Add some two-stroke oil and drive the car home." It is an old fix for a distinct issue. That petrol is still inside that tank afterwards, and whatever it has thinned is not put back.
The next start draws petrol back round your pump from your lines and the fuel filter, where some of that sits after the motor has been run. That's why a DIY tank drain doesn't sort it — a myth. It's also really risky to drain petrol into a can at the roadside.
Why petrol in a diesel takes place so easily
A careless moment is rarely the cause, and nobody means to do it. One way only, since of the nozzles: the smaller petrol one slips inside a diesel filler with almost no resistance, while the diesel one generally won't fit a petrol car. That is how the forecourt makes it simple.
When routine and the vehicle stop matching, it takes place. A motor that is new to you — hired, on loan as a courtesy car, or just bought. Households running one of each, petrol and diesel. The pumps in a different order on a familiar forecourt. Racing for a train at the nearest station and fuelling up en route. A new-to-you diesel Volkswagen Passat, its first fuelling, and a driver accustomed to petrol: exactly when it occurs. Add a back seat full of kids, a phone call or rain, and habit wins.
Preventing petrol in a diesel next time you fill up around Kidwelly
- Not every forecourt in the UK keeps to green for unleaded and black for diesel, though most usually do. Check the petrol pump's label; the colour is only a clue.
- In a car you don't know, look inside the flap over the filler or at the cap before the first fill: many cars state the fuel type there.
- A coloured fob or a sticker on the diesel's key does more than any amount of intending to remember, in a house with one of each.
- Say it before you lift it. On the first fill in a new or hired car, say "diesel" aloud before you take the nozzle off the pump. It seems daft and it works.
- Mistakes like this are simple to make while your mind is on something else, so your phone goes away.
- Up to a point, a misfuel inhibitor helps: some diesels come with a filler built to reject a petrol nozzle, and aftermarket devices exist for the remainder. Treat it as a safety net, then keep checking the pump.
- Stop the moment you realise. Less petrol inside your tank means a weaker blend. It doesn't change what to do next, which is still not to start it.
Kidwelly: already put petrol in a diesel?
Then, there is just a short order of things. Leave it unstarted, with the ignition off as well. Ask the staff to help you push it clear of the pump if you're still on the forecourt, whether that is Murco or somewhere else. What got in, roughly how much, and if it's run: tell us that when you call 0333 366 0103.
If it was AdBlue and not petrol, say so. That's a separate issue — corrosion and deposits instead of lost lubrication — and it has its own page for Kidwelly.
One petrol in a diesel task in Kidwelly costs more than another. Why?
Four separate jobs sit behind the four scenarios above — which is why there is no honest single quote. Which of them you're in is mostly what moves the cost. The proportion matters next, meaning how much of that tank is petrol, and then the location of the car and whether reaching it is safe for a technician.
Three queries come first, before any quote, rather than after — what went in, how much, has it run — and this is the reason. The replies change a range into a straight figure.
About Kidwelly and its setting
Kidwelly is a small coastal town in Carmarthenshire, situated near the mouth of the Gwendraeth estuary. Kidwelly has a long history of industrial and maritime activity, with its harbour and surrounding landscape shaping the town's development. Kidwelly sits at a low elevation of around 8 metres, close to nearby places like Llangadog and Mynyddygarreg. Kidwelly is predominantly composed of terraced housing, reflecting its historic growth as a residential centre.
Fuel drain cover in Kidwelly and across Carmarthenshire
Llangadog, Mynyddygarreg and Kings Wood are among the locations around Kidwelly that the same teams work, answering petrol in diesel jobs across Kidwelly's SA postcode area. A forecourt, a supermarket car park, a lay-by or your own driveway are all places our engineers work, and your car doesn't need to move to us.
Still at the pump around Kidwelly?
Then you're in the best place there can be. Leave it turned off, and ring.