--- title: Explained: Petrol in a Diesel Car Newtown canonical: https://www.petrolinadieselcar.co.uk/petrol-in-diesel/newtown-durham/ location: Newtown county: Durham latitude: 54.570360 longitude: -1.323400 service: Petrol in a Diesel Car updated: 2026-10-03 --- # Should You Worry? Petrol in a Diesel Car in Newtown Likely less than you already are — as long as no one has started the car. Till the ignition primes your pump, the starter turns, or the car is driven, petrol in a diesel tank just waits there and does nothing. Which makes the truthful reply to that first Newtown query — "have I wrecked it?" — normally no. Keep it that way: leave the engine off then ring Petrol in Diesel. What petrol really does to a diesel, how to judge how far it's gone, and how to keep it from happening again: that's the remainder of this page. ## Petrol in a diesel: what does it do to the engine? On its way through a motor, diesel has two jobs. Lubricating comes before burning; it does both. Your high-pressure pump and your injectors are made to very fine clearances, and your diesel passing through them is what keeps those surfaces from grinding against each other. The second task petrol doesn't do at all, and the first it does badly. It is thinner than diesel and removes the lubrication the fuel system hinges on, so a pump running on a petrol mix is a pump wearing itself. And petrol is made to resist igniting under compression, which is the reverse of what a diesel needs from its fuel. That's where the knocking comes from. Put those together and the shape of the issue is clear. The harm is done by movement, not by contact. Where that petrol is only inside your tank, it's an issue of fuel, nothing more. After your pump has been working on that petrol, a mechanical fault has started: whatever is shed by a pump that is wearing down travels downstream to the injectors with the fuel. ## Four scenarios we see in Newtown: how bad is petrol in a diesel? Filled up, and not started: no case is better. The petrol is inside the tank and only the tank, and the job is a drain and a flush where your car stands. This is the one scenario that can only truly take place on a forecourt, since anywhere else your car has been driven to get there. A brief spell of running, or merely the ignition on. Petrol has left your tank and got to your filter and the fuel lines, because your system has been bled. Drain, flush, deal with your filter: still normally simple. Those few miles on the road meant the pump working on fuel diluted by petrol throughout. The work is that tank, your lines, your filter and clean fuel through the entire circuit, and how hard the vehicle was driven counts as much as how far. On the school run to The Oak Tree Academy, the distance is short. Very different again: a run to Durham, under 25 miles away, or some mileage on the A1(M), under 10 miles from Newtown, where the motor kept labouring hard. It complained, and only then stopped: smoke, clattering, a throttle gone soft, an idle gone uneven. The fuel isn't acting like diesel any more, and the motor is saying so. Pull up wherever you are — the verge on Wrensfield Road, a lay-by, a side street — then leave the vehicle where it is. A vehicle stopped soon very seldom has permanent damage, as the fuel drain and the flush, which still come first, sort it out. ## What Newtown drivers get told about petrol in a diesel — and the stories in it It will not be fine. The myth: "Fill it the rest of the way with diesel and it'll be." Nothing is removed by topping up — you're left with a fuller tank, still the same mix. That advice supposes a diesel fuel system tolerates petrol by percentage. It doesn't. Myth: "A current diesel can cope with a bit of petrol." If anything, the reverse. Protection counts more on modern diesels, not less, since their fuel runs through finer parts at higher pressure. The myth that catches people out: if it starts and drives, it must be unharmed. Diesel in a petrol motor normally leaves a motor that will not run: the driver stops, and so does the harm. Nothing looks to have happened when a diesel fed petrol fires up, ticks over and drives away, as it usually will; meanwhile the pump wears. Being able to run is not the same as being fine. Myth: "Add some two-stroke oil and drive the car home." It's an old fix for a separate fault. That petrol is still in your tank after that, and whatever it has thinned isn't put back. Myth: "Drain that tank yourself and you're sorted." After your engine has been run, some of the petrol is no longer inside that tank: it's in your filter and the lines, and it goes straight back through the pump on your next start. Emptying petrol into a can at the roadside is also genuinely dangerous. ## Why petrol in a diesel takes place at all On purpose? Never. Through carelessness? Seldom, if ever. The petrol nozzle is the smaller of the two and slides into a diesel filler with almost no resistance; a diesel nozzle generally will not go into a petrol car at all. The forecourt makes it easy, and the slip runs one way. The moment routine stops matching the car is the moment it takes place. Courtesy car, hire car, or a motor that is brand new. Households running one of each, petrol and diesel. The pumps in a different order on a well-known forecourt. A hurried fill en route to Stockton with a train to catch. Years of petrol vehicles behind you, a diesel Renault Megane in front of you at the forecourt for its first tank — that's when. With rain, a call coming in, or a car full of children to deal with, the hand simply does what it always has. ## Newtown motorists: how to avoid petrol in a diesel next time - Check the petrol pump, not the colour. In the UK unleaded handles are generally green and diesel black, but not on each forecourt. The label is what matters. - In a motor you do not know, look inside the flap over your filler or at the cap before the first fill: many motors print the fuel type there. - Good intentions do less than a sticker or a fob in a vivid colour on the diesel's key when a house has one of each. So mark it. - Say it before you lift it. On the first fill in a new or hired car, say "diesel" aloud before you lift the nozzle off the petrol pump. It seems daft and it works. - Mistakes like this are simple 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 have a filler designed to reject a petrol nozzle, and add-on devices exist for cars without one. They are a safety net, not a reason to stop checking the pump. - Noticing it halfway? Stop at once. A thinner mix follows from less petrol in the tank, but the next step stays the same: don't crank it. ## Already put petrol in a diesel around Newtown? The order of things is brief, then. Don't turn the ignition on, and don't crank it. If you are still at the forecourt — Sainsbury's or anywhere else — ask the staff to help you push the vehicle clear of the pump. What went in, roughly how much, and if it's run: tell us those when you phone 0333 366 0103. Say so if it was AdBlue rather than petrol: it is a separate problem, with its own page for Newtown, because AdBlue brings corrosion and deposits rather than lost protection. ## Why one petrol in a diesel task in Newtown costs more than another The four scenarios above are four separate tasks, so no single quote for this would be honest. Chiefly, your cost moves with which situation you're in. Where your car is matters too, and whether a technician can safely reach it, after the share of petrol to what that tank takes. What was put in, how much, and whether it has run — three questions our technicians ask before pricing, not after, for precisely that reason. A range turns into a straight figure when the replies are in. ## About Newtown itself Newtown is a suburban area located on the riverside in County Durham, with a mix of terraced housing and local amenities. Newtown sits at a low elevation of around 9 metres, near the cities of Durham and Sunderland. Newtown is close to several nearby places, including Primrose Hill, Queens Park, and Newham Grange, and is about 17.7 miles from the city of Durham. Newtown has a population of approximately 6269 residents. ## Newtown and Durham: where our fuel drain cover runs Our teams answering petrol in diesel call-outs around Newtown, in the TS postcode area, equally work the locations around it, Primrose Hill, Queens Park and Newham Grange among them. We drain wherever the car is — your own drive, a lay-by, a supermarket car park, a forecourt — so it does not have to come to us. ## Newtown: still at the pump? Nothing beats it: that is where you are. Phone, and keep it switched off.