--- title: Worried? Petrol in a Diesel Car Firepool canonical: https://www.petrolinadieselcar.co.uk/petrol-in-diesel/firepool-somerset/ location: Firepool county: Somerset latitude: 51.020910 longitude: -3.096700 service: Petrol in a Diesel Car updated: 2026-10-06 --- # Firepool: Petrol in a Diesel Car? How Worried to Be If it hasn't been started, you can worry far less than you likely are. "Have I ruined it?" is the first question anyone in Firepool asks, and the truthful answer is usually no, because petrol left in a diesel tank hurts nothing till it's drawn through the fuel system — by ignition priming, by your starter, or by being driven. Petrol in Diesel is who to ring, with the motor left off, so it remains that way. The rest of this page sets out what petrol actually does to a diesel, how to tell how far it has got, and how to make sure it does not happen to you again. ## The engine and petrol in a diesel: what happens Diesel has two tasks on its way through an engine. Before it combusts, it lubricates — then it ignites. Your high-pressure pump and the injectors are made to extremely fine clearances, and your diesel passing through them is what keeps those surfaces from grinding against one another. Of these two tasks, petrol handles the first badly and the second not at all. It is runnier than diesel and removes the lubrication your fuel system rests on, so a pump running on a petrol mix 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 clattering comes from. Taken together, they show what shape the trouble takes. The damage is done by movement, not by contact. Any tank with petrol in it is a fuel problem. Once the pump has been running on that petrol, a mechanical fault has begun: whatever is shed by a pump that's grinding is carried downstream to your injectors with your fuel. ## Petrol in a diesel in Firepool: how bad is it? Four situations Filled but not once started — the best it gets. Only your tank has petrol in it, so the task is draining that tank and flushing your system where your car sits. This situation can only really happen on a forecourt: anywhere else, the car got there by being driven. Started for a second, or only your ignition on. The system has been primed, so petrol has left the tank and reached the filter and the lines. Still usually simple: drain, flush, and the fuel filter dealt with. Driven a couple of miles. Now your pump has spent those miles labouring on weakened fuel. How hard the car was driven matters as much as how far, and the work covers that tank, your lines, the fuel filter and fresh fuel through the whole circuit. Driving the children to St James Church School is one kind of trip. A run as far as Wells, under 25 miles away, is a very different job. So is any miles on the M5, under 3 miles from Firepool, where the motor has been working hard throughout. Driven on till it complained — clattering, smoke, a ragged idle, a soft throttle. The fuel isn't acting like diesel any more, and your motor is telling you. Stop wherever you are — the verge on Geoffrey Farrant Walk, a lay-by, a side street — then leave the vehicle where it is. A car stopped soon very rarely has lasting damage, since the drain and the flush-through, which still come first, sort it out. ## Firepool motorists and that petrol in a diesel myths they hear False: topping up to full with diesel makes it fine. It doesn't. Nothing comes out when you top up — the tank simply holds more of the same mixture. A diesel fuel system does not tolerate petrol by percentage in the way that advice assumes. If anything, the reverse holds. Myth: "A current diesel can cope with a bit of petrol." Smaller components and higher pressure are how a modern diesel runs its fuel, and that makes the protection matter more, not less. This is the one that fools people. Myth: "If it starts and drives, there's no harm done." Any petrol motor fed diesel normally won't run, so the driver stops and the harm stops with them. Nothing seems to have happened when a diesel fed petrol fires up, ticks over and drives away, which it usually does; meanwhile your pump grinds. A running engine does not mean fine. "A drop of two-stroke oil and drive it home" — a myth, borrowed from a fix from years ago, for a different problem. It doesn't put back what petrol has thinned, and the petrol is still in your tank afterwards. Myth: "Drain the tank yourself and you're sorted." Once the engine has run, some of that petrol is no longer inside the tank: it's in your filter and your lines, and it goes straight back through your pump on the next start. On top of that, petrol emptied into a can by the road is truly dangerous. ## Why petrol in a diesel occurs at all It is seldom carelessness, and no one does it on purpose. The forecourt makes it simple: the petrol nozzle is the smaller of the two, and it slides into a diesel filler with almost no resistance, whilst a diesel nozzle generally won't go into a petrol vehicle at all. So the mistake runs one way. When habit and your car stop matching, it happens. A new vehicle, a hire car or a courtesy car. Two motors on one drive, one petrol, one diesel. Your normal forecourt, its pumps now in a different order. A train to catch, and a rushed fill en route to Taunton. Years of petrol vehicles behind you, a diesel Renault Megane in front of you on the forecourt for its first tank — that's when. Add a back seat full of children, a phone call or rain, and habit wins. ## Next time you fill up in Firepool: preventing petrol in a diesel - A green handle for unleaded and black for diesel is usual in the UK — but not on each forecourt. Trust the label on the petrol pump, not the colour. - In a vehicle you don't know, look inside the flap over the filler or at the cap before the first fill: many vehicles print the fuel type there. - A coloured fob or a sticker on the diesel's key achieves more than any amount of intending to remember, for a home with one of each. - "Diesel", out loud, before you lift the nozzle — every time a new or hired car needs its first tank. It seems silly. It does the trick. - Mistakes like this are simple to make while your mind is on something else, and so your phone goes away. - Add-on devices are available for motors without one, and some diesels come with a filler that won't take a petrol nozzle. Helpful — but a backstop only, never a reason to stop checking the label. - Stop as soon as you realise. Less petrol in that tank makes a weaker mix. It does not change what to do next, which is still not to fire it up. ## Petrol already in a diesel in Firepool? Start here Then the order of things is short. Do not start the vehicle, and do not switch your ignition on. If you are still on the forecourt — Asda Express or anywhere else — ask the staff to help you push it clear of the petrol pump. Next, 0333 366 0103. We'll ask what was put in, about how much, and if it's been run. If it was AdBlue rather than petrol, say so. That is a separate issue — corrosion and deposits instead of lost lubrication — and it has its own page for Firepool. ## Why one petrol in a diesel job around Firepool costs more than another The four situations above are four different jobs, so no single price for this would be fair. Chiefly, your cost shifts with which one you're in. The share counts next, meaning how much of that tank is petrol, followed by the location of the car and whether reaching it is safe for a technician. Three questions come first, before any quote, rather than after — what got in, how much, has it run — and that is the reason. The replies change a range into a straight figure. ## About Firepool and its setting Firepool is a suburban area located on the riverside in Somerset, with a relatively low elevation of 19 metres. Firepool sits near several other local places, including Obridge, North Town, and Rowbarton, and is approximately 23 miles from the city of Wells. Firepool is characterized by a high proportion of flat housing, which is typical of many suburban areas in the South West region. Firepool is also within commuting distance of larger cities, being around 133 miles from London. ## Firepool and Somerset: where our fuel drain cover reaches Obridge, North Town and Rowbarton are among the spots near Firepool that the same teams work, answering petrol in diesel jobs across Firepool's TA postcode area. A forecourt, a supermarket car park, a lay-by or your own driveway are all places our engineers drain, and your car does not need to move to us. ## At the petrol pump in Firepool, right now? Nothing beats it: that's where you now are. Leave the car switched off, and ring.