Winsh-wen: Petrol in a Diesel Car? How Worried to Be
Unstarted? Then less worried than you likely are. Until your ignition primes the pump, your starter turns, or the vehicle is driven, petrol in a diesel tank just waits there and does nothing. Which means the truthful reply to that first Winsh-wen query — "have I ruined it?" — normally no. To leave it that way, ring Petrol in Diesel then leave your motor switched off. Keep reading for three things: the effect petrol has inside a diesel motor, the clues of how far it has got, and the way to make sure you don't do it again.
What petrol in a diesel does to your engine
Passing through a motor, diesel is doing two things at the same time. It burns, and before it ignites it protects. Extremely fine tolerances go into the injectors and the high-pressure pump, and just your diesel running through keeps those surfaces from grinding together.
Of those two jobs, petrol handles the first badly and the second never. It is runnier than diesel and takes away the protection the fuel system rests on, and so a pump running on a petrol mixture is a pump wearing itself. And petrol is made to resist igniting under compression, which is the opposite of what a diesel needs from its fuel. That is where the knocking comes from.
The shape of the problem is clear once you put those together. Contact doesn't do the damage — movement does. All a tank with petrol in it amounts to is a fuel issue. Whatever a worn pump sheds goes on, carried by your fuel, into your injectors downstream, which is why a pump that has been working on that petrol is where a mechanical issue starts.
How bad is petrol in a diesel? Four scenarios our engineers see in Winsh-wen
Filled up, and never started: no case is better. At a forecourt, and really only there, that petrol is still confined to your tank — because anywhere else your car was driven to reach it. The job is emptying and rinsing on the spot.
Started for a moment, or just the ignition on. Once primed, the system has drawn petrol from your tank as far as the filter and the lines. Usually nothing more than emptying, purging and sorting the fuel filter, so still easy.
Those few miles on the road were your pump working on fuel diluted by petrol the whole way. The work is that tank, the fuel lines, the fuel filter and fresh fuel through the whole circuit, and how hard the car was driven counts as much as how far. A school run to the local primary school is one thing. Very different once more: a trip to Swansea, under 3 miles away, or some distance on the M4, under 3 miles from Winsh-wen, where the engine never stopped working hard.
It complained, and only then stopped: smoke, clattering, a throttle gone soft, an idle gone lumpy. That's the engine telling you its fuel no longer is acting like diesel. Stop wherever you are — the verge on Brandon Crescent, a lay-by, a side street — then leave the vehicle there. A car stopped soon very seldom has lasting damage, as the fuel drain and the flush, which still go first, deal with it.
Petrol in a diesel myths Winsh-wen drivers hear
False: topping up to full with diesel makes it fine. It doesn't. A bigger tank of the same mixture is all it gives, since topping up takes out nothing. Percentage is not how a diesel fuel system tolerates petrol, however much that advice assumes.
Not so: a modern diesel copes with a bit of petrol. Rather, the reverse. At higher pressure, through finer components: that is how a newer diesel handles its fuel, so the lubrication counts more, not less.
This is the one that fools people. Myth: "If it starts and drives, there is no harm done." The driver of a petrol engine fed diesel normally stops, since it will not run, and the harm stops there. Feed petrol to a diesel and it normally fires up, ticks over and drives away as if nothing has happened — all while its pump is wearing. Running doesn't mean fine.
"A drop of two-stroke oil and drive it home" — a myth, borrowed from a fix from years ago, for a distinct fault. That petrol is still inside your tank afterwards, and whatever it has diluted isn't put back.
Once your engine has run, part of the petrol is in the filter and the fuel lines, not that tank — and the next start pulls it right back through your pump. So the myth "drain that tank yourself and you are sorted" doesn't stand up. It is also really dangerous to drain petrol into a can by the roadside.
How it happens: petrol in a diesel
It is rarely carelessness, and no one does it on purpose. The petrol nozzle is the smaller of the two and slides into a diesel filler with almost no resistance; a diesel nozzle mostly will not go into a petrol motor at all. The forecourt makes it simple, and the error runs one way.
When habit and your car stop matching, it takes place. Hire cars, courtesy cars, and vehicles that are new to you. Two cars on one drive, one petrol, one diesel. Your normal forecourt, its pumps suddenly in a different order. Racing for a train at Llansamlet and fuelling up en route. The first fill-up in a diesel Renault Megane after years of driving petrol is precisely the moment it takes place. The hand does what it has always done once you add rain, a phone call or a back seat full of children.
Winsh-wen motorists: how to prevent petrol in a diesel next time
- Not every forecourt in the UK keeps to green for unleaded and black for diesel, even if most generally do. Read the pump's label; the colour is just a clue.
- Check your filler flap. Many motors state the fuel inside the flap or on the cap. Look at it on the first fill in a motor you don't know.
- One of each in the household? Mark your key to the diesel — a bright fob, a sticker — because meaning to remember isn't enough.
- Before the nozzle comes off the pump the first time you fill a hired or new vehicle, say "diesel" aloud. Silly, yes, but 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 block a petrol nozzle, and devices you can add exist for cars without one. Such an inhibitor helps up to a point — as a backstop, not a reason to stop checking the petrol pump.
- The moment you notice, stop: less petrol inside the tank makes a weaker blend. What to do next doesn't change, though — still do not fire it up.
Petrol already in a diesel around Winsh-wen? Begin here
Short and simple, then, is the order of things. Do not start the vehicle, and don't switch your ignition on. If you're still on the forecourt — Tesco or anywhere else — ask the staff to help you push the car away from the pump. Call 0333 366 0103 next, with three answers — your fuel, the rough quantity, and whether it's run.
AdBlue, not petrol? Then say so. Corrosion and deposits, not lost lubrication, make it a different problem — Winsh-wen has a page just for it.
Why one petrol in a diesel job around Winsh-wen costs more than another
Four different tasks sit behind the four situations above — which is why there is no fair single price. The situation itself does most of the work of moving your cost. The ratio matters next, meaning how much of the tank is petrol, followed by the location of the vehicle and whether getting to it is safe for a technician.
Before any quote, not after, come three questions: the fuel that was put in, its amount, and if it's run. That is why. The replies change a range into a straight figure.
About Winsh-wen itself
Winsh-wen is a suburban area located on the coast near Swansea, with a mix of semi-detached housing and local amenities. Winsh-wen sits at an elevation of 68 metres, overlooking the surrounding coastline and nearby communities such as Cwm and Trallwn. Winsh-wen is close to the city of Swansea, being only 2.8 miles away, and is part of the wider Swansea urban area. Winsh-wen has a population of approximately 3619 residents, living in a variety of semi-detached homes.
Winsh-wen and Swansea: where our fuel drain cover reaches
The teams answering petrol in diesel call-outs in Winsh-wen, in the SA postcode area, also work the locations around it, Cwm, Cae-maes-y-bar and Trallwn among them. No need to bring the vehicle to us. Forecourts, supermarket car parks, lay-bys and your own drive are all places we drain.
In Winsh-wen and still at the pump?
The best position there is, then — that's where you are. Leave it switched off, and ring.