--- title: Worried? Petrol in a Diesel Car Shepton Mallet canonical: https://www.petrolinadieselcar.co.uk/petrol-in-diesel/shepton-mallet-somerset/ location: Shepton Mallet county: Somerset latitude: 51.189810 longitude: -2.547320 service: Petrol in a Diesel Car updated: 2026-10-11 --- # Shepton Mallet: Petrol in a Diesel Car? How Worried to Be If it hasn't been started, worry less than you probably are. "Have I ruined it?" is the first thing anyone around Shepton Mallet asks, and the truthful answer is generally no, because petrol left in a diesel tank hurts nothing till it's drawn through your fuel system — by ignition priming, by the starter, or by being driven. To leave the vehicle that way, phone Petrol in Diesel and leave the motor switched off. Keep reading for three things: the effect petrol has inside a diesel engine, the signs of how far it has spread, and the way to make sure you don't do it again. ## What petrol in a diesel does to the motor Passing through a motor, diesel is doing two jobs at the same time. It lubricates to begin with, and only then does it burn. The high-pressure pump and your injectors are built to very fine tolerances, and the diesel passing through them is what stops those surfaces from wearing down against one another. Petrol does the first job poorly and the second not at all. Being less viscous than diesel, petrol strips out the lubrication a fuel system needs, leaving a pump on the mixture wearing itself. It is equally made to resist igniting under compression — the opposite of what a diesel needs — which is why you hear the clattering. Put those together and the shape of the problem is clear. The harm is done by movement, not by contact. Petrol in a tank is a fuel fault. Once the pump has been working on that petrol, a mechanical issue has started: anything shed by a pump that's wearing down travels onward to the injectors with the fuel. ## Shepton Mallet, petrol in a diesel: four situations, from mild to major The best case there is: filled up, never started. Only the tank has petrol in it, so the task is draining your tank and flushing the fuel system where your car stands. This situation can only really take place on a forecourt: anywhere else, the car got there by being driven. Started for a second, or just the ignition on. Once primed, the system has drawn petrol out of your tank as far as your filter and your lines. That's generally still an easy job — a drain, a flush, and the filter dealt with. Those few miles driven meant your pump working on fuel diluted by petrol the whole way. Tank, lines, filter, then fresh fuel run through the entire system: that's the work, and the way the vehicle was driven matters as much as the mileage. Short trips, such as the school run to St Paul's Church of England VC Junior School, are one thing. Any distance on the M5, under 25 miles from Shepton Mallet, means your engine has worked hard throughout, and a run to Wells, under 5 miles away, makes a very different task as well. Driven on till it complained — rattling, smoke, a lumpy idle, a dead throttle. That is your motor telling you its fuel no longer is acting like diesel. Stop where you are — on the verge on Commercial Road, at the kerb, down a side road — and don't move it. A vehicle pulled over soon very rarely has permanent damage, because the fuel drain and the flush, which still come first, take care of it. ## What Shepton Mallet people get told about petrol in a diesel — and the myths in it Myth: topping up to full with diesel makes it fine. It does not. Nothing is removed by topping up — you are left with a fuller tank, still the same mix. A diesel fuel system does not accept petrol by percentage in the way that guidance presumes. Myth: a newer diesel copes with a bit of petrol. If anything, the reverse. More precise parts and higher pressure are the way a current diesel runs its fuel, and that makes the protection matter more, not less. This is the one that catches motorists. Myth: "If it starts and drives, there's no harm done." Feed diesel to a petrol motor and it usually won't run, and so the motorist stops — and the damage stops with them. Feed petrol to a diesel and it generally fires up, ticks over and drives away as if nothing happened — all the while its pump is wearing. Being able to run is not the same as being fine. "A drop of two-stroke oil and drive it home" — a myth, taken from a fix from years ago, for a distinct issue. It does not put back what petrol has diluted, and that petrol is still in your tank afterwards. Myth: "Drain your tank yourself and you're sorted." After the motor has run, some of the petrol is no longer inside your tank: it's in the fuel filter and the lines, and it goes right back through your pump at the next start. Emptying petrol into a can at the kerbside is also really hazardous. ## How it happens: petrol in a diesel A careless moment is rarely the cause, and no one means to do it. One way only, because of the nozzles: the smaller petrol one slides inside a diesel filler with almost no resistance, while the diesel one mostly won't fit a petrol car. That is how the forecourt makes it straightforward. It occurs when habit and the car stop matching. Courtesy car, hire car, or a vehicle that's brand new. A household with one petrol and one diesel on the drive. A familiar forecourt with the pumps in a different order. Fuelling up in a hurry on the way to Castle Cary, with a train to catch. Precisely the moment it takes place: after years of driving petrol, a driver fills a diesel Renault Megane for the first time. With rain, a call arriving, or a car full of children to deal with, your hand just does what it always has. ## Next time you fill up in Shepton Mallet: preventing petrol in a diesel - A green handle for unleaded and black for diesel is normal in the UK — but not on every forecourt. Trust the label on the petrol pump, not the colour. - Many motors state the fuel type inside the filler flap or on the cap, and so check it on the first fill in a vehicle you don't know. - Good intentions do less than a sticker or a fob in a bright colour on the diesel's key when a house has one of each. So label it. - It seems daft and it works: on the first fill in a new or hired car, say "diesel" out loud before you take the nozzle off the petrol pump. - Whilst you're thinking about something else, this is an easy mistake to make — so put the phone away. - Add-on devices exist for vehicles without one, and some diesels come with a filler that won't accept a petrol nozzle. Helpful — but a safety net only, never a reason to stop checking the label. - Stop as soon as you notice. Less petrol inside that tank makes a weaker mix. It does not change what to do next, which is still not to start the car. ## Petrol already in a diesel in Shepton Mallet? Begin here Short and simple, then, is the order of things. Starting it is out, and so is turning on the ignition. Ask the attendants to help you roll it clear of the petrol pump if you're still on the forecourt, whether that is Tesco or anywhere else. What got in, about how much, and whether it's run: tell us that when you call 0333 366 0103. Say so if it was AdBlue rather than petrol: it is a separate issue, with its own page for Shepton Mallet, since AdBlue brings corrosion and deposits rather than lost protection. ## Why one petrol in a diesel task around Shepton Mallet costs more than another The four situations above are four different tasks, so no single quote for this would be fair. Which of them you are in is mostly what moves the cost. Next it's the share — how much petrol got in against how much that tank holds — and then where your car is and whether our van can get to it safely. Before any quote, not after, come three questions: the fuel that was put in, its amount, and if it's run. That is why. A range becomes a straight figure once those replies are in. ## About Shepton Mallet and its setting Shepton Mallet is a town in the South West of England, situated on the River Sheppey in Somerset, with a population of around 10132 people. Shepton Mallet sits at an elevation of 145 metres, near the city of Wells and close to smaller settlements like Field, West Shepton, and Bowlish. Shepton Mallet has a mix of housing types, with semi-detached homes being particularly prevalent. Shepton Mallet is located about 106.7 miles west of London, making it a significant urban centre in the region. ## Shepton Mallet and Somerset: where our fuel drain cover runs Our teams answering petrol in diesel call-outs around Shepton Mallet, in the BA postcode area, also work the spots near it, Field, West Shepton and Bowlish included. A forecourt, a supermarket car park, a lay-by or your own drive are all spots we drain, and the vehicle doesn't need to come to us. ## In Shepton Mallet and still at the pump? Nothing beats it: that's where you are. Ring, and keep it switched off.