Fron-Bache: Petrol in a Diesel Car? How Worried to Be
Probably less than you already are — as long as no one has started it. Petrol resting in a diesel tank does nothing to the engine till something draws it through your fuel system — your ignition priming the pump, your starter, or driving itself. So the fair answer to the first question everyone around Fron-Bache asks, "have I ruined it?", is usually no. To keep the car that way, ring Petrol in Diesel and leave your motor alone. What petrol really does to a diesel, how to gauge how far it has gone, and how to keep it from happening again: that's the remainder of this page.
Inside the motor: what petrol in a diesel does
Passing through a motor, diesel is doing two things at the same time. Before it combusts, it lubricates — and then it ignites. What keeps the surfaces inside the high-pressure fuel pump and the fuel injectors from wearing against each other is your diesel passing through them — they're built to very fine tolerances.
Of these two tasks, petrol handles the first poorly and the second not at all. It's runnier than diesel and removes the protection the system hinges on, 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 reverse of what a diesel needs from its fuel. That is where the rattling comes from.
Put those together and the shape of the trouble is plain. Contact does not do the harm — movement does. Where the petrol is only inside that tank, it's an issue of fuel, nothing more. After the pump has been running on that petrol, a mechanical fault has started: anything shed by a pump that's grinding travels downstream to your injectors with your fuel.
Petrol in a diesel in Fron-Bache: how bad is it? Four situations
Filled but never started — as good as it gets. That petrol is inside the tank and only your tank, and the job is a drain and a flush where the car sits. This is the one scenario that can only truly occur on a forecourt, since anywhere else your car has been driven to get there.
Ignition on, or started for a second. The fuel system has been bled, and so petrol has left that tank and got to the filter and your lines. Drain, flush, see to the filter: still usually simple.
The pump now spent a couple of miles on thinned fuel — that is what driving the vehicle meant. How hard the vehicle was driven counts as much as how far, and the work covers that tank, your lines, the fuel filter and clean fuel through the whole system. Short trips, such as the school run to the local primary school, are one matter. Very different a second time: a run to Wrexham, under 10 miles away, or some mileage on the M53, under 25 miles from Fron-Bache, where the motor never stopped running hard.
Rattling, a ragged idle, smoke, a throttle gone soft: driven till it complained. The fuel is not behaving like diesel any more, and the motor is saying so. Pull up where you are — on the verge on Fron Castell, at the kerb, down a side road — and don't move it. What goes first is still the fuel drain and flush-through, and that deals with it, with permanent damage very uncommon when a vehicle is pulled over early.
Petrol in a diesel myths Fron-Bache people hear
False: topping up to full with diesel makes it fine. It doesn't. Nothing is removed when you top up — your tank simply carries more of the same mixture. A diesel fuel system doesn't accept petrol by percentage in the way that guidance assumes.
"Newer diesels can handle a little petrol" — a myth, and closer to the opposite. At higher pressure, through smaller parts: that's how a newer diesel handles its fuel, so the lubrication matters for more, not less.
This is the one that catches motorists. Myth: "If it starts and drives, there is no damage done." A petrol motor fed diesel generally won't run, and so the driver stops and the damage stops with them. Feed petrol to a diesel and it usually fires up, ticks over and pulls away like nothing happened — all the while its pump is wearing. Running isn't the same as fine.
Myth: "Add some two-stroke oil and drive it home." It is an outdated workaround for a distinct fault. It doesn't put back what petrol has diluted, and the petrol is still inside that tank afterwards.
"Drain it yourself and you are sorted" — a myth, since after it's been running some petrol sits in the filter and lines, ready to go right back through your pump at your next start. It is also really dangerous to drain petrol into a can at the roadside.
How does petrol in a diesel happen?
Carelessness is rarely the cause, and no one means to do it. The petrol nozzle is the smaller 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 easy, and the slip runs one way.
It happens when routine and your car stop matching. Any car that's new to you — a hire car, on loan as a courtesy car, or just bought. Households running one of each, petrol and diesel. The pumps in a different order on a familiar forecourt. A train to catch, and a hurried fill en route to Chirk. The first fill-up in a diesel Volkswagen Golf after years of driving petrol is exactly the moment it occurs. With rain, a call coming in, or a car full of children to deal with, the hand just does what it always has.
Preventing petrol in a diesel next time you fill up in Fron-Bache
- The label is what matters, and so read the pump rather than the colour: in the UK unleaded handles are usually green and diesel black, but not on every forecourt.
- Many cars state the fuel inside your filler flap or on the cap, so check it on the first fill in any car you don't know.
- A coloured fob or a sticker on your diesel's key does more than any amount of intending to remember, for a home with one of each.
- It seems silly and it does the trick: on your first fill in a new or hired car, say "diesel" out loud before you lift the nozzle off the pump.
- Mistakes like this are easy to make while your mind is on something else, so the phone goes away.
- Add-on devices exist for cars without one, and some diesels come with a filler that won't take a petrol nozzle. Useful — but a backstop only, never a reason to stop checking the label.
- Spotting it halfway? Stop there and then. A thinner mix follows from less petrol inside that tank, yet your next stage remains the same: don't start the vehicle.
Fron-Bache: already put petrol in a diesel?
Short and simple, then, is the order of things. Don't fire it up, and don't turn your ignition on. If you are still at the forecourt — Texaco or anywhere else — ask the attendants to help you roll the car clear of the pump. Then phone 0333 366 0103 and tell us what was put in, about how much, and whether it has run.
If it was AdBlue instead of petrol, say so. That is a different problem — corrosion and deposits instead of lost lubrication — and it has its own page for Fron-Bache.
What makes one Fron-Bache petrol in a diesel task cost more than the next
Four different jobs sit behind the four situations above — which is why there is no fair single price. What moves your cost is chiefly which of them you're in. Where the car is matters too, and whether our van can safely reach it, after the share of petrol to what that tank takes.
Three queries come first, before quoting, rather than after — what got in, how much, has it run — and this is the reason. Those answers turn a range into a straight figure.
About Fron-Bache, briefly
Fron-Bache is a locality in Denbighshire, situated on the banks of a river at an elevation of 122 metres, with detached housing being the predominant type of accommodation. Fron-Bache lies near the towns of Llangollen and Wrexham, and is also close to the smaller settlements of Pen-y-Coed and Geufron. Fron-Bache is located in a rural area, with the nearest city, Wrexham, being approximately 9 miles away. Fron-Bache has a population of around 878 people, according to recent estimates.
Fuel drain cover across Denbighshire, Fron-Bache included
The teams answering petrol in diesel jobs around Fron-Bache, in the LL postcode area, equally work the places around it, Llangollen, Pen-y-Coed and Geufron included. The vehicle doesn't need to move to us: our engineers drain at a forecourt, in a supermarket car park, in a lay-by or on your own drive.
Still at the petrol pump in Fron-Bache?
The best place there is, then — that is where you are. Call, and keep it switched off.