Biscovey: Petrol in a Diesel Car? How Worried to Be
Far less than you probably are, provided it hasn't been started. Till the ignition primes your pump, the starter turns, or your car is driven, petrol in a diesel tank simply waits there and does nothing. Which means the truthful reply to that first Biscovey query — "have I ruined it?" — usually no. To keep the vehicle that way, call Petrol in Diesel and leave your motor alone. The remainder of this page sets out what petrol actually does to a diesel, how to judge how far it has got, and how to make sure it does not happen to you a second time.
What petrol in a diesel does to the engine
Passing through an engine, diesel is doing two things at once. It combusts, and before it ignites it lubricates. What stops the surfaces inside the high-pressure fuel pump and your injectors from wearing down against one another is the diesel passing through them — they are made to very fine clearances.
The second task petrol doesn't do at all, and the first it does poorly. Being less viscous than diesel, petrol strips out the protection a fuel system needs, so a pump 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 hear the clattering.
Seen together, they show what shape the problem has. Not contact but movement is what does the damage. Petrol in a tank is a fuel issue. The beginning of a mechanical problem is a pump that has been running on that petrol — and whatever a worn pump sheds moves on with your fuel to the injectors beyond it.
Petrol in a diesel around Biscovey: how bad is it? Four situations
The best case there is: filled up, never started. Being on a forecourt is what makes this possible: elsewhere, the car has been driven there to begin with. With that petrol held in the tank alone, it is emptied and rinsed on the spot, and nothing more is needed.
Ignition on, or started for a moment. Once primed, your system has drawn petrol from your tank as far as your filter and your lines. Still usually straightforward: drain, flush, and your filter dealt with.
Driven a couple of miles. Now your pump has spent those miles labouring on thinned fuel. Tank, lines, filter, then clean fuel run through the entire circuit: that is this work, and the way your car was driven matters as much as the miles. On the school run to Biscovey Academy, the miles is short. A run as far as Truro, under 25 miles away, is a very different job. So is any mileage on the M5, over 50 miles from Biscovey, where the motor has been working hard throughout.
Driven until it protested. Clattering, an uneven idle, smoke, a throttle that has gone soft. The fuel isn't acting like diesel any more, and your engine is saying so. Whether it is the verge on Lamellyn Road, a lay-by or a side street, stop where you are and leave it. Lasting damage is very uncommon when a vehicle is pulled over early, and the fuel drain and flush-through that still come first sort it out.
What Biscovey motorists get told about petrol in a diesel — and the myths in it
Myth: "Fill it the rest of the way with diesel and it will be fine." It will not. Nothing is removed by topping up — you're left with a bigger tank, still the same mix. Percentage is not how a diesel fuel system copes with petrol, however much that guidance supposes.
Myth: "A modern diesel can cope with a bit of petrol." If anything, the opposite. A modern diesel runs its fuel through smaller parts at higher pressure, which makes the lubrication matter more, not less.
This is the one that catches people. Myth: "If it starts and drives, there's no harm done." Diesel in a petrol motor normally leaves a motor that will not run: the driver stops, and so does the damage. A diesel fed petrol usually starts, ticks over and drives away as if nothing has happened, while your pump wears. A running engine does not mean fine.
"A drop of two-stroke oil and drive it home" — a myth, taken from a fix from years ago, for a distinct issue. None of what petrol weakened is put back by it — and afterwards, your tank still contains that petrol.
"Drain it yourself and you are sorted" — a myth, because after it has been running some petrol lies in your filter and lines, waiting to go right back through the pump on the next start. On top of that, petrol cleared into a can by the road is truly hazardous.
Petrol in a diesel: how does it take place?
Nobody does it on purpose, and it is seldom carelessness. One way only, because of the nozzles: the slimmer petrol one slips inside a diesel filler with almost no resistance, while the diesel one generally will not fit a petrol motor. That is how the forecourt makes it easy.
The moment habit stops matching the car is the moment it takes place. Any vehicle that is new to you — a hire car, on loan as a courtesy car, or brand new. One petrol and one diesel on the driveway of the same household. A familiar forecourt with the pumps in a different order. Filling up in a rush on the way to Par, with a train to catch. The first fill-up in a diesel Volkswagen Passat after years of driving petrol is precisely the moment it takes place. Your hand does what it has always done once you add rain, a phone call or a back seat full of kids.
How to prevent petrol in a diesel on your next fill-up around Biscovey
- Not every forecourt in the UK follows green for unleaded and black for diesel, even if most usually do. Read the petrol pump's label; the colour is just a clue.
- The first fill in a new car is the time to check your filler flap — on it, or on the cap, plenty of cars state which fuel they take.
- Good intentions count for less than a sticker or a fob in a bright colour on the diesel's key when a home has one of each. So mark it.
- Before the nozzle leaves the petrol pump the first time you fill a hired or new vehicle, say "diesel" out loud. Daft, perhaps, yet it works.
- Thinking about something else is when this becomes an easy mistake to make, and so put your phone away and keep your mind on the petrol pump.
- Some diesels come with a filler built to reject a petrol nozzle, and devices you can add exist for cars without one. Such an inhibitor helps up to a point — as a safety net, not a reason to stop checking the petrol pump.
- The moment you realise, stop: less petrol inside your tank makes a thinner mixture. What to do next does not change, though — still don't fire it up.
Put petrol in a diesel around Biscovey already?
Short and simple, then, is the order of things. Leave it unstarted, with the ignition off too. The staff at the forecourt — whether at BP itself or wherever you filled up — will usually help push it clear of the pump if you ask. Then call 0333 366 0103 and tell us what was put in, about how much, and whether it's run.
If it was AdBlue and not petrol, say so. That is a separate fault — corrosion and deposits rather than lost lubrication — and it has its own page for Biscovey.
One petrol in a diesel task around Biscovey costs more than another. Why?
An honest single quote does not exist here: four scenarios, four separate jobs. The scenario itself does most of the work of moving the cost. Where your car is matters too, and whether a technician can safely get to it, after the share of petrol to what that tank takes.
Three queries come first, before quoting, rather than after — what was put in, how much, has it run — and that is the reason. Given those replies, you get a straight figure rather than a range.
About Biscovey and its setting
Biscovey is a coastal locality in Cornwall, situated near the town of Par and the village of St Blazey, at an elevation of 34 metres above sea level. Biscovey lies within a short distance of several nearby places, including St Blazey Gate, St Blazey, and Bodelva. Biscovey is characterised by its semi-detached housing stock and is located approximately 15.7 miles from the city of Truro. Biscovey has a population of around 2524 residents.
Biscovey and Cornwall: where our fuel drain cover reaches
Our teams answering petrol in diesel jobs in Biscovey, in the PL postcode area, also work the places around it, St Blazey Gate, St Blazey and Bodelva among them. Our technicians 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.
Biscovey: still at the petrol pump?
Then, you could not be in a better spot. Keep it off. Ring.