How Worried Should You Be? Petrol in a Diesel Car in Torry
Far less than you probably are, if it hasn't been started. "Have I ruined it?" is the first question everyone in Torry asks, and the truthful answer is usually no, since petrol resting in a diesel tank hurts nothing till it is dragged through the system — by ignition priming, by the starter, or by being driven. To keep it like that, ring Petrol in Diesel and leave your motor switched off. What petrol really does to a diesel, how to gauge how far it has travelled, and how to stop it from happening a second time: that is the remainder of this page.
Inside your engine: what petrol in a diesel really does
Passing through a motor, diesel is doing two things at the same time. It lubricates first, and after that does it burn. Very fine clearances go into the injectors and the high-pressure pump, and just the diesel flowing through stops those surfaces grinding together.
The second job petrol doesn't do at all, and the first it does poorly. It is runnier than diesel and removes the lubrication your fuel system rests on, and so a pump running on a petrol blend is a pump wearing itself. And petrol is designed 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 plain once you put those together. The harm is done by movement, not by contact. All a tank with petrol in it amounts to is a fuel fault. The start of a mechanical one is a pump that has been running on that petrol — and whatever a worn pump sheds moves on with your fuel to your injectors beyond it.
Four scenarios we see in Torry: how bad is petrol in a diesel?
Filled up, not once started. The best case there can be. That petrol is inside your tank and only that tank, and the task is a drain and a flush where the car sits. This is the one scenario that can only really occur on a forecourt, since anywhere else your car has been driven to get there.
A brief spell of running, or merely the ignition on. The system has been primed, so petrol has left that tank and reached the fuel filter and the lines. That is normally still a simple job — a drain, a flush, and the fuel filter seen to.
A few miles driven, and the pump has spent every one of them running on weakened fuel. Tank, lines, filter, then fresh fuel put through the whole system: that is the work, and the way your car was driven matters as much as the distance. Short trips, like the school run to the local primary school, are one matter. Any mileage on the M90, over 50 miles from Torry, means your engine has worked hard throughout, and a run to Aberdeen, under 3 miles away, makes a very different job too.
It complained, and only then stopped: smoke, clattering, a throttle gone soft, an idle gone ragged. What you are hearing is the motor reporting fuel that no longer acts like diesel. Whether it is the verge on Victoria Road, a lay-by or a side road, stop there and leave it. What goes first is still the drain and flush, and that sorts it out, with permanent damage very unusual when a vehicle is stopped soon.
What Torry drivers get told about petrol in a diesel — and the myths in it
Myth: "Fill it the rest of the way with diesel and it'll be fine." It will not. Nothing comes out when you top up — the tank simply holds more of the same blend. A diesel fuel system does not accept petrol by percentage in the way that advice supposes.
If anything, the reverse holds. Myth: "A modern diesel can cope with a bit of petrol." Lubrication counts more on current diesels, not less, because their fuel passes through more precise parts at higher pressure.
"It starts, it drives, so no harm done" — the myth that trips up more motorists than any other. Feed diesel to a petrol motor and it generally won't run, so the driver stops — and the harm stops with them. Whilst the pump wears, a diesel fed petrol normally starts, idles and drives away as if nothing has happened. Running isn't the same as fine.
"A drop of two-stroke oil and drive it home" — a myth, taken from a fix from years ago, for a separate fault. None of what petrol diluted gets put back by it — and afterwards, the tank still holds that petrol.
The next start sends petrol back round the pump from the fuel lines and the fuel filter, where some of that ends up once the motor has been run. That is why draining your tank yourself doesn't sort it — a myth. Clearing petrol into a can by the kerbside is also genuinely risky.
How it happens: petrol in a diesel
It's seldom carelessness, and no one does it on purpose. The forecourt makes it simple: the petrol nozzle is the slimmer of the two, and it slips into a diesel filler with almost no resistance, whilst a diesel nozzle mostly won't go into a petrol motor at all. So the slip runs one way.
It happens when routine and the car stop matching. Hire cars, courtesy cars, and vehicles that are new to you. A household with one petrol and one diesel on the drive. The pumps in a different order on a familiar forecourt. Rushing for a train outside Aberdeen and fuelling up en route. Years of petrol cars behind you, a diesel Volkswagen Golf in front of you at the forecourt for its first tank — that's when. The hand does what it has always done when you add rain, a phone call or a back seat full of kids.
Next time you fill up in Torry: preventing petrol in a diesel
- Not every forecourt in the UK keeps to green for unleaded and black for diesel, even if most generally do. Read the petrol pump's label; the colour is only a clue.
- The first fill in a strange car is the time to check your filler flap — inside it, or on the cap, many cars state the fuel they take.
- A coloured fob or a sticker on the diesel's key achieves more than any amount of meaning to remember, for a household with one of each.
- "Diesel", out loud, before you lift the nozzle — each time a new or hired car needs its first tank. It seems silly. It does the trick.
- Tuck the phone away. This is an easy mistake to make whilst you are thinking about something else.
- Some diesels come with a filler built to reject a petrol nozzle, and devices you can add are available 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.
- Less petrol makes a thinner mix, and so stop as soon as you realise — while remembering that your next stage is unchanged. It is still not to crank it.
Petrol already in a diesel around Torry? Begin here
In that case, there is only a short order of things. Don't switch the ignition on, and do not fire it up. Yet on the forecourt, at BP or anywhere else? Ask the staff to help you push the vehicle away from the pump. Next, 0333 366 0103. We'll ask what got in, roughly how much, and if it's been run.
Corrosion and deposits are the trouble with AdBlue, where petrol brings lost lubrication. So if it was AdBlue, say so — and see its own Torry page.
One petrol in a diesel task in Torry costs more than another. Why?
There's no fair single price for this, since the four scenarios above are four separate tasks. Mostly, the cost shifts with which situation you are in. Two things follow that: the petrol that was put in as a share of what that tank takes, then the place your car is in and whether a technician can get to it safely.
What got in, how much, and if it's run — three questions our technicians ask before quoting, not after, for precisely that reason. Their replies are what turn a range into one firm number.
About Torry, briefly
Torry is a coastal suburban area in Aberdeen City, situated approximately 1 mile from Aberdeen city centre. Torry occupies a low-lying area at around 26 metres above sea level, with nearby neighbourhoods including Footdee, Tullos, and Balnagask. Torry is predominantly composed of flat-type housing, which is common in many Scottish urban areas. Torry is home to around 6457 residents, according to approximate population figures.
Torry and Aberdeen City: where our fuel drain cover runs
Torry rests in the AB postcode area, and our teams that answer petrol in diesel calls there work the spots near it as well — Footdee, Tullos and Balnagask among them. The vehicle doesn't need to move to us: our technicians drain on a forecourt, in a supermarket car park, in a lay-by or on your own drive.
At the pump in Torry, right now?
No position is better: that is where you now are. Phone, and leave it turned off.