--- title: Worried? Petrol in a Diesel Car New Fletton canonical: https://www.petrolinadieselcar.co.uk/petrol-in-diesel/new-fletton-cambridgeshire/ location: New Fletton county: Cambridgeshire latitude: 52.562890 longitude: -0.248560 service: Petrol in a Diesel Car updated: 2026-10-09 --- # Petrol in a Diesel Car in New Fletton: How Worried Should You Be? Not started? Then less anxious than you likely feel. Petrol resting in a diesel tank does nothing to the motor till something draws it through your fuel system — the ignition priming your pump, your starter, or driving itself. So the fair answer to the first query everyone around New Fletton asks, "have I ruined it?", is generally no. Petrol in Diesel is who to phone, with the motor kept off, so it remains that way. Further down, this page sets out what petrol actually does inside a diesel, how far it may have got, and how to stop it happening to you a second time. ## Petrol in a diesel: what does it do to the motor? On its way through a motor, diesel has two tasks. Before it burns, it protects — then it ignites. Built to extremely fine gaps, the injectors and your pump depend on your diesel moving through them to keep their surfaces from wearing against one another. Petrol handles the first job poorly and the second not at all. The knocking comes from petrol being made not to ignite when compressed, which is precisely the reverse of what a diesel needs. On top of that it is runnier than diesel, it strips out the lubrication the fuel system depends on, and any pump working on that blend is wearing itself. Put those together and the shape of the trouble is plain. It's movement that causes the harm, not contact. Where the petrol is only in your tank, it's a problem of fuel, nothing more. A pump that has been running on that petrol is the beginning of a mechanical one, and whatever a worn pump sheds travels on with your fuel to the injectors downstream. ## Four scenarios our technicians see around New Fletton: how bad is petrol in a diesel? Filled up, not once started. The best case there can be. The petrol is in the tank and only that tank, and the task is a drain and a flush where your car stands. This is the one scenario that can only really occur at a forecourt, since anywhere else your car has been driven to get there. Started for a moment, or just your ignition on. Once primed, your system has pulled petrol out of that tank up to your filter and the lines. Still usually straightforward: drain, flush, and the filter dealt with. Driven a few miles. Now the pump has spent these miles labouring on diluted fuel. Miles is only half of it; how hard it was driven counts equally. Either way this work includes that tank, the lines, the fuel filter and fresh fuel through the whole circuit. A school run to St Augustine's CofE (Voluntary Aided) Junior School is one matter. A run as far as Peterborough, under a mile away, is a very different job. So is any distance on the A1(M), under 5 miles from New Fletton, where the motor has been labouring hard throughout. Driven until it complained. Knocking, an uneven idle, smoke, a throttle that has gone soft. That's your engine telling you its fuel has stopped acting like diesel. Stop wherever you are — the verge on Orchard Mews, a lay-by, a side street — and leave the vehicle there. Permanent damage is very unusual if a vehicle is stopped quickly, and the drain and flush that still come first sort it out. ## What New Fletton drivers get told about petrol in a diesel — and the stories in it Myth: "Fill it the rest of the way with diesel and it'll be fine." It will not. A bigger tank of the same mix is all you get, because topping up removes nothing. The assumption behind the guidance — that diesel fuel systems tolerate petrol by percentage — is wrong. "Modern diesels can handle a little petrol" — a myth, and closer to the opposite. A current diesel runs its fuel through more precise parts at higher pressure, which makes the protection count more, not less. This is the one that fools motorists. Myth: "If it starts and drives, there's no harm done." Feed diesel to a petrol engine and it generally won't run, so the motorist stops — and the damage stops with them. Nothing looks to have happened when a diesel fed petrol fires up, ticks over and drives away, as it usually will; meanwhile the pump grinds. Fine and running are not the same thing. An old workaround for a different problem is behind this one. Myth: "Add some two-stroke oil and drive the car home." It does not put back what petrol has weakened, and that petrol is still inside that tank after that. Once the motor has run, part of that petrol sits in your filter and the fuel lines, not that tank — and your next start pulls it right back through your pump. So the myth "drain your tank yourself and you're sorted" does not stand up. Emptying petrol into a can by the roadside is also really dangerous. ## Why petrol in a diesel takes place so easily Carelessness is rarely the cause, and nobody means to do it. A diesel nozzle generally will not fit a petrol car, yet the narrower petrol nozzle goes into the filler of a diesel nearly without resistance — so forecourts make this one error easy, and just in one direction. It occurs when routine and your car stop matching. Any car that's new to you — hired, 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. Filling up in a hurry en route to Peterborough, with a train to catch. Years of petrol cars behind you, a diesel Volkswagen Golf in front of you on the forecourt for its first tank — that is when. Add a back seat full of kids, a phone call or rain, and the hand wins. ## Preventing petrol in a diesel next time you fill up around New Fletton - The label is what matters, and so check the pump rather than the colour: in the UK unleaded handles are normally green and diesel black, but not on every forecourt. - The first fill in a strange vehicle is the time to check your filler flap — on it, or on the cap, many motors state the fuel they take. - One of each in the house? Label the key to the diesel — a bright fob, a sticker — because meaning to remember isn't enough. - Before the nozzle leaves the pump the first time you fill a hired or new motor, say "diesel" aloud. Silly, perhaps, yet it works. - Mistakes like this are straightforward to make while your mind is on something else, and so the phone goes away. - A misfuel inhibitor helps, up to a point. Some diesels come with a filler built to refuse a petrol nozzle, and add-on devices are available for cars without one. They are a backstop, not a reason to stop checking the pump. - As soon as you notice, stop: less petrol inside the tank makes a weaker blend. What to do next doesn't change, though — still do not crank it. ## Put petrol in a diesel in New Fletton already? Short and simple, then, is the order of things. Leave it unstarted, with your ignition off as well. Ask the staff to help you push it away from the petrol pump if you're still on the forecourt, whether that's Esso or somewhere else. Call 0333 366 0103 next, with three facts — your fuel, the approximate quantity, and if it has run. Corrosion and deposits are the issue with AdBlue, whereas petrol brings lost protection. So if it was AdBlue, say so — and read its own New Fletton page. ## Why one petrol in a diesel task around New Fletton costs more than another The four scenarios above are four separate tasks, so no single quote for this would be fair. The scenario itself does most of the work of moving your cost. Beyond that it is the share — how much petrol was put in against how much that tank takes — and after that where the car is and whether our van can get to it safely. What was put in, how much, and if it has run — three queries our technicians ask before quoting, not after, for exactly that reason. Their answers are what turn a range into one firm number. ## About New Fletton and where it is New Fletton is a suburban area located on the eastern bank of the River Nene in Cambridgeshire, with nearby settlements including Woodston and Old Fletton. New Fletton sits at a low elevation of around 13 metres, close to the city of Peterborough. New Fletton has a mix of housing types, but semi-detached homes are particularly prevalent in the area. New Fletton is situated approximately 73 miles north of London, making it a commuter base for those working in the capital. ## New Fletton and Cambridgeshire: where our fuel drain cover runs Woodston, Old Fletton and Peterborough are among the locations near New Fletton that the same vans work, answering petrol in diesel calls across New Fletton's PE postcode area. The vehicle does not need to move to us: we drain on a forecourt, in a supermarket car park, in a lay-by or on your own driveway. ## At the pump around New Fletton, right now? The best place there is, then — that is where you are. Keep it off. Ring.