Should You Worry? Petrol in a Diesel Car in Morfa
Not started? Then less anxious than you probably are. "Have I ruined it?" is the first question everyone around Morfa asks, and the honest answer is normally no, because petrol resting in a diesel tank harms nothing until it's dragged through the system — by ignition priming, by your starter, or by being driven. Keep it that way: leave your engine off and ring Petrol in Diesel. What petrol actually does to a diesel, how to judge how far it's travelled, and how to keep it from happening again: that's the remainder of this page.
What petrol in a diesel does to the engine
Two jobs fall to diesel on its journey through a motor. Before it combusts, it protects — then it combusts. Very fine gaps are built into your injectors and your high-pressure pump, and only the diesel running through keeps those surfaces from grinding together.
Of these two tasks, petrol handles the first badly and the second never. The knocking comes from petrol being made not to ignite when compressed, which is precisely the reverse of what a diesel needs. On top of that it is thinner than diesel, it strips out the protection your system hinges on, and any pump working on such a mixture is wearing itself.
The shape of the trouble is clear when you put those together. Contact doesn't do the damage — circulation does. Where that petrol is only inside your tank, it's a fault of fuel, nothing more. Whatever a worn pump sheds goes on, carried by your fuel, into your injectors downstream, which is why a pump that has worked on that petrol is where a mechanical problem starts.
Four situations we see around Morfa: how bad is petrol in a diesel?
Fuelled, and not started: nothing beats it. Just the tank has petrol in it, so the job is emptying that tank and purging your system where the car stands. This situation can only really take place on a forecourt: anywhere else, the vehicle got there by being driven.
The ignition turned on, or a short start. Petrol has come out of the tank and got to the filter and the lines, because your system has been primed. Still usually easy: drain, flush, and the filter dealt with.
Driven a couple of miles. Now your pump has spent these miles working on thinned fuel. Tank, lines, filter, then fresh fuel run through the entire system: that is the work, and the way the car was driven counts as much as the miles. A school run to the local primary school is one matter. Very different again: a trip to Swansea, under 10 miles away, or some mileage on the M4, under 5 miles from Morfa, where the motor kept labouring hard.
Driven on till it complained — knocking, smoke, an uneven idle, a soft throttle. The engine is telling you your fuel is no longer acting like diesel. Pull up wherever you are — the verge on Morfa Roundabout, a lay-by, a side street — and leave the vehicle where it is. Permanent damage is very uncommon when a vehicle is pulled over early, and the fuel drain and flush-through that still go first sort it out.
What Morfa drivers get told about petrol in a diesel — and the myths in it
False: topping up to full with diesel makes it fine. It does not. A bigger tank of the same mixture is all you get, since topping up removes nothing. Percentage isn't how a diesel fuel system tolerates petrol, whatever that advice presumes.
Myth: a modern diesel copes with a bit of petrol. Rather, the reverse. A newer diesel runs its fuel through smaller components at higher pressure, which makes the lubrication count more, not less.
"It starts, it drives, and so there is no harm" — the myth that trips up more drivers than any other. The driver of a petrol motor fed diesel normally has no choice but to stop, since it will not run, and the damage stops there. A diesel fed petrol usually starts, ticks over and drives away as though nothing has happened, whilst your pump grinds. A running engine doesn't mean fine.
Not so: a two-stroke additive makes it safe to drive home. It is an old workaround, supposed for another issue. The petrol is still inside that tank after that, and whatever it has thinned isn't put back.
The next start draws petrol back round the pump from the fuel lines and the fuel filter, where some of it sits once the motor has been run. That's why draining your tank yourself does not sort it — a myth. On top of that, petrol cleared into a can by the road is genuinely hazardous.
How does petrol in a diesel occur?
No one does it on purpose, and it is rarely carelessness. A diesel nozzle mostly will not fit a petrol vehicle, but the smaller petrol nozzle goes into the filler of a diesel almost without resistance — so forecourts make this one mistake easy, and only in that direction.
Routine and your car getting out of step is how it happens. Any motor that is new to you — hired, on loan as a courtesy car, or just bought. One petrol and one diesel on the drive of the same household. Your ordinary forecourt, its pumps now in a different order. A train to catch, and a rushed fill en route to Llanelli. The first fill-up in a diesel Renault Megane after years of driving petrol is precisely the moment it takes place. With rain, a call coming in, or a car full of children to deal with, the hand just does what it always has.
Morfa motorists: how to avoid petrol in a diesel next time
- Green for unleaded and black for diesel is normal in the UK — yet not on every forecourt. Go by the label on the pump, not the colour.
- Plenty of vehicles state the fuel type inside the filler flap or on the cap, so check it on the first fill in a car you do not know.
- A coloured fob or a sticker on your diesel's key does more than any amount of meaning to remember, for a household with one of each.
- Before the nozzle comes off the pump the first time you fuel a hired or new motor, say "diesel" out loud. Silly, perhaps, but it works.
- Thinking about something else is when this becomes an easy mistake to make, so put the phone away then keep your mind on the petrol pump.
- A misfuel inhibitor helps, up to a point. Some diesels come with a filler designed to reject a petrol nozzle, and add-on devices are available for vehicles without one. They are a safety net, not a reason to stop reading the pump.
- Noticing it mid-fill? Stop there and then. A thinner mixture follows from less petrol inside your tank, yet the next step stays the same: don't fire it up.
Already put petrol in a diesel in Morfa?
The order of things is brief, then. Don't turn the ignition on, and don't start it. Yet on the forecourt, at Tesco or anywhere else? Ask the staff to help you push the car clear of the petrol pump. Next, 0333 366 0103. We'll ask what was put in, about how much, and if it's been run.
Corrosion and deposits are the trouble with AdBlue, where petrol means lost lubrication. So if it was AdBlue, say so — and read its own Morfa page.
Why one petrol in a diesel job around Morfa costs more than another
There's no honest single price for this, since the four scenarios above are four different tasks. Which of them you are in is chiefly what moves the cost. Beyond that it is the proportion — how much petrol was put in against how much that tank holds — and after that where the car is and whether a van can get to it safely.
Three questions come first, before quoting, instead of after — what went in, how much, has it run — and this is the reason. A range becomes a straight figure when those replies are in.
About Morfa, for a moment
Morfa is a small coastal suburban area in Carmarthenshire, situated near the city of Swansea. Morfa sits at a low elevation of around 5 metres, close to the sea and within a short distance of nearby places such as Ty-isaf and Trostre. Morfa has a mix of housing types, but terraced housing is predominant in the area. Morfa is located approximately 9 miles from Swansea, making it a commuter base for the city.
Morfa and Carmarthenshire: where our fuel drain cover runs
Petrol in diesel call-outs around Morfa — part of the SA postcode area — go to vans that likewise cover the spots about it, Ty-isaf, Pen-y-fan and Trostre among them. We drain where your vehicle is — your own driveway, a lay-by, a supermarket car park, a forecourt — so it never needs to come to us.
In Morfa and still at the petrol pump?
Then, you could not be in a better position. Call, and keep it turned off.