Coppermine: Petrol in a Diesel Car? How Worried to Be
Less than you likely are, if it hasn't been started. Till your ignition primes your pump, the starter cranks, or your vehicle is driven, petrol in a diesel tank just sits there and does nothing. Which makes the truthful reply to that first Coppermine query — "have I wrecked it?" — normally no. Keep it like that: leave your motor off then phone Petrol in Diesel. Below, this page sets out what petrol actually does inside a diesel, how far it may have got, and how to stop it happening to you again.
What petrol in a diesel does to the engine
Passing through an engine, diesel does two things at once. Lubricating comes before burning; it does both. What stops the surfaces inside the high-pressure pump and your injectors from grinding against one another is your diesel flowing through them — they're designed to very fine tolerances.
Of these two jobs, petrol handles the first badly and the second not at all. A pump working on a petrol mixture is wearing itself out, because petrol is runnier than diesel and strips out the protection your fuel system depends on. Petrol is also designed to resist igniting under compression — the opposite of what a diesel wants from its fuel — and that is where the knocking comes.
Seen together, they make clear what shape the issue has. It's movement that causes the damage, not contact. Where the petrol is only inside your tank, it's an issue of fuel, nothing more. Once the pump has been labouring on that petrol, a mechanical issue has started: anything shed by a pump that is wearing travels downstream to your injectors with the fuel.
Coppermine, petrol in a diesel: four situations, from mild to significant
Fuelled, and not started: nothing beats it. Being on a forecourt is what makes this the case: elsewhere, the car has been driven there to begin with. With that petrol held inside your tank alone, it's cleared and purged right where it stands, and nothing more is needed.
A moment's running, or merely the ignition on. The system has been bled, so petrol has left the tank and reached your filter and the lines. Drain, flush, deal with your filter: still normally straightforward.
Those few miles driven meant your pump working on fuel thinned by petrol the whole way. Distance is only half of it; how hard it was driven matters just as much. Either way this work runs to your tank, the lines, your filter and fresh fuel through the whole circuit. Driving the kids to the local primary school is one sort of trip. Any miles on the M8, under 15 miles from Coppermine, means the motor working hard throughout, and a run to Glasgow, under 25 miles away, makes a very different job as well.
Knocking, a ragged idle, smoke, a throttle gone soft: driven until it complained. That is the engine telling you its fuel has stopped acting like diesel. Whether it is the verge on Mathie Crescent, a lay-by or a side road, stop where you are then leave it. A car stopped quickly very seldom has permanent damage, as the drain and the flush, which still go first, take care of it.
What Coppermine motorists get told about petrol in a diesel — and the stories in it
Myth: topping up to full with diesel makes it fine. It does not. Nothing comes out when you top up — that tank just carries more of the same mixture. A diesel fuel system doesn't tolerate petrol by percentage in the way that guidance supposes.
Not so: a current diesel copes with a bit of petrol. If anything, the opposite. Protection counts more on current diesels, not less, because their fuel passes through smaller parts at higher pressure.
The myth that catches people off guard: if it starts and drives, it must be unharmed. Any petrol motor fed diesel normally won't run, so the motorist stops and the harm stops with them. While the pump wears, a diesel fed petrol usually starts, ticks over and drives away as if nothing has happened. Being able to run is not proof of being fine.
"A drop of two-stroke oil and drive it home" — a myth, taken from a fix from years ago, for a different fault. None of what petrol diluted is put back by it — and later, your tank still holds the petrol.
"Drain it yourself and you're sorted" — a myth, because after it's been running some petrol lies in the fuel filter and lines, ready to go straight back through the pump on the next start. Draining petrol into a can by the kerbside is also really risky.
Petrol in a diesel: how does it happen?
On purpose? Never. Through carelessness? Seldom, if ever. A diesel nozzle mostly won't fit a petrol vehicle, yet the narrower petrol nozzle goes into the filler of a diesel nearly without resistance — so forecourts make this one mistake easy, and just in that direction.
The moment habit stops matching the car is the moment it takes place. A new motor, a hire car or a courtesy car. Households running one of each, petrol and diesel. Your usual forecourt, its pumps now in a different order. Fuelling up in a rush on the way to Gourock, with a train to catch. Exactly the moment it takes place: after years of driving petrol, a driver fills a diesel Renault Megane for the first time. Throw in rain, a phone call or a back seat full of children, and the hand repeats what it has always done.
Preventing petrol in a diesel next time you fill up around Coppermine
- The label is what matters, so read the pump rather than the colour: in the UK unleaded handles are normally green and diesel black, but not on each forecourt.
- Inspect your filler flap. Plenty of cars state the fuel type inside the flap or on the cap. Look at it on the first fill in a car you don't know.
- One of each in the home? Mark your key to the diesel — a bright fob, a sticker — because intending to remember is not enough.
- Say it before you lift it. On your first fill in a new or hired car, say "diesel" aloud before you take the nozzle off the pump. It sounds daft and it does the trick.
- Mistakes like this are easy to make whilst your mind is on something else, so the phone goes away.
- Some diesels come with a filler built to reject a petrol nozzle, and devices you can add are available for motors without one. Such an inhibitor helps up to a point — as a backstop, not a reason to stop checking the petrol pump.
- Stop the moment you realise. Less petrol inside that tank makes a thinner mix. It does not change what to do next, which is still not to start the car.
Coppermine: already put petrol in a diesel?
Then the order of things is brief. Starting it is out, and so is switching on the ignition. Still at the forecourt, at BP or anywhere else? Ask the staff to help you push the vehicle clear of the petrol pump. What was put in, roughly how much, and whether it's run: tell us that when you ring 0333 366 0103.
If it was AdBlue instead of petrol, say so. That's a separate fault — corrosion and deposits rather than lost protection — and it has its own page for Coppermine.
Coppermine petrol in a diesel tasks: why one costs more than another
Four separate jobs lie behind the four scenarios above — which is why there's no fair single price. Which of them you are in is chiefly what moves your cost. Beyond that it is the ratio — how much petrol got in against how much that tank takes — and after that where the car is and whether a van can reach it safely.
Before any quote, not after, come three questions: the fuel that got in, its volume, and whether it has run. That is why. The replies change a range into a straight figure.
About Coppermine, for a moment
Coppermine is a coastal suburban area in Inverclyde, situated near the cities of Glasgow and Greenock. Coppermine sits at an elevation of 55 metres, overlooking the Firth of Clyde, and is characterized by its predominantly flat-type housing. Coppermine is located near other suburban areas such as Midton, Coves, and Ashton, and is approximately 23 miles west of Glasgow.
Fuel drain cover across Inverclyde, Coppermine included
Midton, Coves and Ashton are among the places near Coppermine that the same teams work, answering petrol in diesel jobs across Coppermine's PA postcode area. A forecourt, a supermarket car park, a lay-by or your own drive are all locations our technicians work, and your vehicle doesn't need to come to us.
Still at the pump in Coppermine?
Then you're in the best spot there is. Keep it switched off, then ring.