Should You Worry? Petrol in a Diesel Car in Boghead
Not started? Then less anxious than you probably are. "Have I wrecked it?" is the first question anyone in Boghead asks, and the truthful answer is normally no, because petrol resting in a diesel tank harms nothing till it is dragged through the fuel system — by ignition priming, by your starter, or by driving. Petrol in Diesel is who to call, with your engine left off, and so it remains that way. Below, you will find what petrol really does inside a diesel, how far it may have got, and how to stop it happening to you a second time.
Inside the engine: what petrol in a diesel really does
On its way through a motor, diesel has two tasks. Lubricating comes before burning; it does both. What keeps the surfaces inside the high-pressure pump and the injectors from wearing down against one another is the diesel flowing through them — they are made to extremely fine gaps.
Of those two tasks, petrol handles the first poorly and the second not at all. Being less viscous than diesel, petrol strips away the protection a fuel system needs, so a pump running on the mixture to wear itself. It's equally made to resist igniting under compression — the reverse of what a diesel needs — which is why you hear the knocking.
Put those together and the shape of the problem is clear. It is movement that causes the damage, not contact. Petrol in a tank is a fuel fault. Whatever a worn pump sheds travels on, borne by the fuel, into the injectors further along, which is why a pump that has been working on that petrol is where a mechanical problem starts.
Petrol in a diesel around Boghead: how serious is it? Four cases
Filled up, not once started. The best case there is. The petrol is in that tank and only your tank, and the task is a drain and a flush where your car sits. This is the one situation that can only really happen at a forecourt, as anywhere else the car has been driven to get there.
A brief spell of running, or merely your ignition on. Petrol has come out of that tank and got to the filter and the lines, because your system has been bled. That's normally still an easy task — a drain, a flush, and the fuel filter seen to.
Driven a few miles. Now the pump has spent those miles labouring on diluted fuel. Tank, lines, filter, then clean fuel run through the whole circuit: that is this work, and the way your car was driven counts as much as the miles. On the school run to the local primary school, the distance is small. Any distance on the M80, under 3 miles from Boghead, means your engine working hard throughout, and a run to Glasgow, under 5 miles away, makes a very different job as well.
Driven until it complained. Knocking, a lumpy idle, smoke, a throttle that has gone soft. The motor is telling you the fuel is no longer behaving like diesel. Whether it is the verge on Forest Gardens, a lay-by or a side road, stop there and leave it. What comes first is still the drain and flush, and that takes care of it, with long-term damage very unusual when a car is stopped early.
Myths Boghead motorists hear about petrol in a diesel
It will not be fine. The myth: "Fill it the rest of the way with diesel and it will be." A fuller tank of the same mixture is all it gives, since topping up removes nothing. That advice presumes a diesel fuel system tolerates petrol by percentage. It doesn't.
Myth: "A newer diesel can cope with a bit of petrol." If anything, the reverse. More precise components and higher pressure are how a newer diesel runs its fuel, and that makes the lubrication matter more, not less.
"It starts, it drives, so no harm done" — the myth that catches more drivers than any other. Diesel in a petrol motor generally means a motor that won't run: the driver stops, and so does the harm. Feed petrol to a diesel and it generally starts, ticks over and pulls away as if nothing happened — all the while its pump is wearing. Fine and running are not the same at all.
An outdated workaround for a distinct problem is behind this one. Myth: "Add some two-stroke oil and drive the car home." None of what petrol thinned gets put back by it — and later, that tank still contains that petrol.
Myth: "Drain the tank yourself and you are sorted." Once the engine has been run, some of the petrol is no longer inside that tank: it is in the filter and your lines, and it goes straight back through the pump on the next start. It's also genuinely dangerous to drain petrol into a can at the roadside.
How petrol ends up: petrol in a diesel
Carelessness is rarely the cause, and no one means to do it. One way only, because of the nozzles: the smaller petrol one slips inside a diesel filler with almost no resistance, whereas the diesel one generally won't fit a petrol car. That is how the forecourt makes it simple.
The moment routine stops matching your car is the moment it occurs. Hire cars, courtesy cars, and cars 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. A train to catch, and a rushed fill en route to Lenzie. A new-to-you diesel Volkswagen Tiguan, its first fuelling, and a motorist accustomed to petrol: precisely when it occurs. Throw in a back seat full of kids, a phone call or rain, and habit takes over.
Preventing petrol in a diesel next time you fill up in Boghead
- 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.
- The first fill in an unfamiliar car is the time to check the filler flap — inside it, or on the cap, plenty of vehicles state the fuel they take.
- Label the 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 meaning to remember.
- Before the nozzle leaves the pump the first time you fuel a hired or new vehicle, say "diesel" aloud. Daft, perhaps, yet it works.
- Mistakes like this are easy to make whilst your mind is on something else, and so the phone goes away.
- A misfuel inhibitor helps, up to a point. Some diesels have a filler designed to block a petrol nozzle, and add-on devices exist for vehicles without one. They are a backstop, not a reason to stop checking the petrol pump.
- The moment you realise, stop: less petrol in your tank means a thinner mix. What to do next doesn't change, though — still do not fire it up.
Boghead: already put petrol in a diesel?
The order of things is short, then. Don't switch the ignition on, and don't start it. The attendants at the forecourt — whether at JET itself or wherever you filled up — will usually help push it clear of the petrol pump if you ask. Next, 0333 366 0103. We will ask what was put in, about how much, and if it's been run.
Corrosion and deposits are the problem with AdBlue, whereas petrol brings lost protection. So if it was AdBlue, say so — and see its own Boghead page.
What makes one Boghead petrol in a diesel task cost more than the next
The four scenarios above are four different jobs, so no single price for this would be honest. What shifts your cost is mostly which of them you're in. Where your car is matters too, and whether our van can safely get to it, after the proportion of petrol to what the tank holds.
Ahead of any quote, not after, we ask three queries: the fuel that went in, the amount, and whether it's run. That's why. Those replies turn a range into a straight figure.
About Boghead
Boghead is a suburban area situated on the riverside in East Dunbartonshire, with a mix of detached housing and local amenities. Boghead sits at an elevation of 66 metres, close to the nearby places of High Gallowhill, The Greens, and Lenzie. Boghead is located near Glasgow, Scotland's largest city, which is approximately 4.6 miles away. Boghead has a population of around 1458 residents, living in predominantly detached homes.
Across East Dunbartonshire and around Boghead: fuel drain cover
Petrol in diesel call-outs in Boghead — part of the G postcode area — go to vans that likewise cover the spots round it, High Gallowhill, The Greens and Lenzie included. The car doesn't need to come to us: our technicians drain at a forecourt, in a supermarket car park, in a lay-by or on your own drive.
Boghead: still at the petrol pump?
The best place there is, then — that's where you are. Call, and leave it switched off.