--- title: New Buildings: Petrol in a Diesel Car, Explained canonical: https://www.petrolinadieselcar.co.uk/petrol-in-diesel/new-buildings-northamptonshire/ location: New Buildings county: Northamptonshire latitude: 51.989340 longitude: -1.206280 service: Petrol in a Diesel Car updated: 2026-10-14 --- # New Buildings: Petrol in a Diesel Car? How Worried to Be Probably less than you already are — as long as no one has started the vehicle. Until your ignition primes the pump, the starter turns, or your car is driven, petrol in a diesel tank simply waits there and does nothing. Which means the truthful reply to that first New Buildings question — "have I wrecked it?" — usually no. To leave it like that, phone Petrol in Diesel and leave the engine alone. What petrol actually does to a diesel, how to gauge how far it's travelled, and how to stop it from happening a second time: that's the rest of this page. ## Petrol in a diesel: what does it do to the motor? On its way through a motor, diesel does two jobs. Before it burns, it lubricates — and then it ignites. Made to very fine tolerances, the injectors and your pump rely on your diesel flowing through them to stop their surfaces wearing against one another. The second job petrol doesn't do at all, and the first it does poorly. The clattering comes from petrol being designed 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 away the protection your system hinges on, and any pump running on such a mix is wearing itself. The shape of the issue is plain when you put those together. Contact doesn't do the harm — circulation does. Petrol in the tank is a fuel issue. Whatever a worn pump sheds goes on, borne by your fuel, into your injectors downstream, which is why a pump that has been working on that petrol is where a mechanical issue begins. ## Four situations our technicians see around New Buildings: how bad is petrol in a diesel? Fuelled, and not started: nothing beats it. At a forecourt, and really only there, that petrol is still confined to that tank — since anywhere else your car was driven to get to it. The task is emptying and cleaning on the spot. Your ignition turned on, or a brief start. With your system primed, your lines and filter already contain petrol that came from the tank. Still generally easy: drain, flush, and the filter sorted. Driven a few miles. Now the pump has spent those miles running on thinned fuel. Distance is only half of it; how hard it was driven matters just as much. Either way the work includes your tank, the lines, the filter and fresh fuel through the whole system. Short trips, like the school run to Croughton All Saints CofE Primary School, are one matter. Very different again: a run to Oxford, under 25 miles away, or some miles on the M40, under 3 miles from New Buildings, where the motor kept running hard. It protested, and only then stopped: smoke, clattering, a throttle gone soft, an idle gone lumpy. That's the engine telling you its fuel no longer is behaving like diesel. Leave it wherever it has stopped: a lay-by, a quiet street, the verge on Portway. What goes first is still the drain and flush-through, and that takes care of it, with permanent damage very rare if a vehicle is pulled over early. ## Myths New Buildings people hear about petrol in a diesel False: topping up to full with diesel makes it fine. It does not. Topping up takes out nothing; it gives you a bigger tank of the same mix. The idea behind that advice — that diesel fuel systems accept petrol by percentage — is wrong. "Modern diesels can handle a little petrol" — a myth, and nearer the reverse. A newer diesel runs its fuel through finer parts at higher pressure, which makes the lubrication count more, not less. This is the one that catches motorists. Myth: "If it starts and drives, there's no damage done." Any petrol engine fed diesel normally won't run, so the driver stops and the harm stops with them. Feed petrol to a diesel and it generally fires up, ticks over and pulls away as if nothing happened — all while its pump is wearing. Running does not mean fine. "A drop of two-stroke oil and drive it home" — a myth, taken from a fix from years ago, for a different problem. None of what petrol weakened gets put back by it — and later, your tank still contains the petrol. "Drain it yourself and you're sorted" — a myth, because after it's been running some petrol sits in the fuel filter and lines, ready to go straight back through the pump on your next start. It's also genuinely hazardous to drain petrol into a can by the kerbside. ## Petrol in a diesel: how does it take place? Nobody does it on purpose, and it is seldom carelessness. The forecourt makes it simple: the petrol nozzle is the narrower 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 routine and your car stop matching, it happens. Courtesy car, hire car, or a car that is new. A household with one petrol and one diesel on the driveway. The pumps in a different order on a familiar forecourt. A train to catch, and a hurried fill on the way to Kings Sutton. The first fill-up in a diesel Renault Megane after years of driving petrol is precisely the moment it occurs. Throw in a back seat full of kids, a phone call or rain, and the hand takes over. ## Next time you fill up around New Buildings: avoiding petrol in a diesel - Read the pump, not the colour. In the UK unleaded handles are generally green and diesel black, yet not on each forecourt. The label is what counts. - The first fill in a strange car is the time to check your filler flap — on it, or on the cap, many motors state which fuel they take. - One of each in the house? Mark your key to the diesel — a bright fob, a sticker — because meaning to remember isn't enough. - It seems daft and it works: on your first fill in a new or hired car, say "diesel" out loud before you take the nozzle off the pump. - Mistakes like this are simple to make while your mind is on something else, and so the phone goes away. - Up to a point, a misfuel inhibitor helps: some diesels have a filler designed to block a petrol nozzle, and aftermarket devices exist for the rest. Count it as a backstop, then keep reading the petrol pump. - Stop as soon as you realise. Less petrol inside that tank makes a thinner mixture. It doesn't change what to do next, which is still not to crank it. ## Already put petrol in a diesel in New Buildings? In that case, there's only a short order of things. Starting it is out, and so is switching on your ignition. The attendants on the forecourt — whether at A E Prentice itself or wherever you filled up — will normally help push it away from the petrol pump if you ask. Then call 0333 366 0103 and tell us what was put in, about how much, and whether it's run. If it was AdBlue and not petrol, say so. That is a separate problem — corrosion and deposits rather than lost protection — and it has its own page for New Buildings. ## One petrol in a diesel job around New Buildings costs more than another. Why? There's no honest single price for this, since the four scenarios above are four different jobs. Chiefly, the cost moves with which situation you are in. Two things come after that: the petrol that was put in as a share of what the tank holds, then the place the vehicle is in and whether a technician can reach it safely. Ahead of any quote, not after, we ask three questions: the fuel that got in, the amount, and whether it's run. That is why. A range turns into a straight figure once those replies are in. ## About New Buildings and where it is New Buildings is a small locality in Northamptonshire, situated inland at an elevation of around 122 metres. New Buildings lies near the villages of Croughton, Tusmore, and Souldern, and is approximately 16.5 miles from Oxford. New Buildings has a population of around 529 people, with a predominance of semi-detached housing. New Buildings is also within commuting distance of London, being about 56.9 miles from the capital. ## Fuel drain cover across Northamptonshire, New Buildings included Petrol in diesel calls around New Buildings — part of the NN postcode area — go to vans that likewise cover the places about it, Croughton, Tusmore and Souldern among them. A forecourt, a supermarket car park, a lay-by or your own driveway are all locations our technicians work, and your car does not need to come to us. ## New Buildings: still at the pump? Nothing beats it: that is where you now are. Phone, and leave it turned off.