Boddam: Petrol in a Diesel Car? How Worried to Be
Provided it has not been started, you can worry less than you probably are. "Have I wrecked it?" is the first question everyone around Boddam asks, and the honest answer is usually no, since petrol left in a diesel tank harms nothing until it is dragged through your fuel system — by ignition priming, by the starter, or by driving. Petrol in Diesel is who to call, with your engine kept off, so it stays that way. Below, this page sets out what petrol actually does inside a diesel, how far it might have gone, and how to stop it happening to you a second time.
Petrol in a diesel: what does it do to your engine?
Passing through an engine, diesel does two jobs at once. It lubricates first, and after that does it burn. Built to very fine tolerances, your injectors and the pump depend on your diesel moving through them to stop their surfaces wearing against one another.
Badly at the first, not at all at the second: that's petrol. A pump running on a petrol mix is wearing itself out, because petrol is thinner than diesel and takes away the lubrication the fuel system relies on. Petrol is also made to resist igniting under compression — the opposite of what a diesel needs from its fuel — and that's where any rattling starts.
Put those together and the shape of the issue is plain. Contact doesn't do the damage — circulation does. Petrol in the tank is a fuel issue. The start of a mechanical one is a pump that has been running on that petrol — and whatever a worn pump sheds travels on with your fuel to your injectors beyond it.
How serious is petrol in a diesel? Four scenarios we see in Boddam
The best case there is: filled up, not once started. Being on a forecourt is what makes this the case: elsewhere, your car has been driven there to begin with. With that petrol kept in the tank alone, it's emptied and rinsed right where it stands, and nothing more is needed.
Started for a second, or just the ignition on. Your system has been primed, and so petrol has left your tank and got to your filter and your lines. Still normally easy: drain, flush, and the fuel filter dealt with.
Those few miles on the road were your pump labouring on fuel thinned by petrol throughout. Distance is only half of that; how hard it was driven matters equally. Either way the work includes that tank, the fuel lines, the filter and clean fuel through the whole system. On the school run to the local primary school, the distance is short. Getting as far as Aberdeen, under 50 miles away, makes a very different job — as does any miles on the M90, over 50 miles from Boddam, with your engine running hard the whole time.
It complained, and only then stopped: smoke, knocking, a throttle gone soft, an idle gone uneven. What you are hearing is the engine reporting fuel that no longer acts like diesel. Pull up where you are — on the verge on Seaview Road, at the kerb, down a side road — and do not move it again. Lasting damage is very unusual when a vehicle is stopped early, and the fuel drain and flush-through that still come first take care of it.
What Boddam people get told about petrol in a diesel — and the myths in it
It will not be fine. The myth: "Fill it the rest of the way with diesel and it will be." Nothing comes out when you top up — your tank just carries more of the same blend. The assumption behind that advice — that diesel fuel systems tolerate petrol by percentage — is wrong.
Myth: "A modern diesel can cope with a bit of petrol." If anything, the reverse. A newer diesel sends its fuel through more precise components at higher pressure, which makes the lubrication count more, not less.
"It starts, it drives, so no harm done" — the myth that catches most drivers than any other. Any petrol motor fed diesel normally won't run, so the driver stops and the damage stops with them. While the pump wears, a diesel fed petrol normally starts, idles and drives away as though nothing has happened. Fine and running aren't the same thing.
"A drop of two-stroke oil and drive it home" — a myth, taken from a fix from years ago, for a separate issue. The petrol is still inside the tank afterwards, and what it has weakened isn't put back.
The next start sends petrol back round the pump out of your lines and the fuel filter, where some of it ends up once the engine has been run. That's why a DIY tank drain does not sort it — a myth. Also, a can of petrol filled at the roadside is genuinely risky.
Why petrol in a diesel occurs at all
Carelessness is seldom the cause, and no one means to do it. The petrol nozzle is the narrower of the two and slips into a diesel filler with almost no resistance; a diesel nozzle generally won't go into a petrol car at all. The forecourt makes it simple, and the mistake runs one way.
It happens when routine and the car stop matching. Any motor that's new to you — hired, on loan as a courtesy car, or just bought. A household with one petrol and one diesel on the driveway. A familiar forecourt with the pumps in a different order. Filling up in a hurry on the way to the nearest station, with a train to catch. Years of petrol cars behind you, a diesel Renault Clio in front of you at the forecourt for its first tank — that's when. Throw in a back seat full of children, a phone call or rain, and habit takes over.
Preventing petrol in a diesel next time you fill up in Boddam
- The label is what matters, and so read the pump rather than the colour: in the UK unleaded handles are normally green and diesel black, yet not on each forecourt.
- The first fill in a new car is the time to check the filler flap — on it, or on the cap, plenty of motors state which fuel to use.
- Mark your key. In a house with one of each, a coloured fob or a sticker on the diesel's key does more than any amount of intending to remember.
- Say it before you lift it. On your first fill in a new or hired car, say "diesel" out loud before you lift the nozzle off the pump. It seems daft and it works.
- Whilst you're thinking about something else, this is an easy mistake to make — so tuck your phone away.
- A misfuel inhibitor helps, up to a point. Some diesels have a filler built to reject a petrol nozzle, and add-on devices exist for motors without one. They are a backstop, not a reason to stop reading the petrol pump.
- Stop as soon as you realise. Less petrol inside your tank means a thinner blend. It doesn't change what to do next, which is still not to crank it.
Put petrol in a diesel in Boddam already?
Short and simple, then, is the order of things. Do not switch the ignition on, and do not fire it up. If you're still at the forecourt — Shell or anywhere else — ask the attendants to help you push the car clear of the 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, whereas petrol means lost lubrication. So if it was AdBlue, say so — and see its own Boddam page.
What makes one Boddam petrol in a diesel task cost more than the next
There is no honest single quote for this, because the four situations above are four separate jobs. The situation itself does most of the work of moving the cost. Where the vehicle is counts too, and whether our van can safely get to it, after the ratio of petrol to what your tank holds.
That is why we ask three queries before quoting instead of after: what went in, how much, and whether it's run. Those answers change a range into a straight figure.
About Boddam, briefly
Boddam is a small coastal village in Aberdeenshire, situated approximately 25 miles north of Aberdeen. Boddam sits at a low elevation of around 28 metres, looking out to the North Sea. Boddam has a mix of housing types, but semi-detached homes are particularly common in the village. Boddam is located near other small settlements, including Stirling Village and Sandfordhill.
Boddam and Aberdeenshire: where our fuel drain cover runs
Boddam sits in the AB postcode area, and the teams that answer petrol in diesel jobs there work the spots around it as well — Stirling Village, Sandfordhill and Invernettie among them. We drain where your vehicle is — your own drive, a lay-by, a supermarket car park, a forecourt — so it does not have to come to us.
In Boddam and still at the pump?
Then you're in the best place there can be. Ring, and leave it switched off.