--- title: Worried? Petrol in a Diesel Car Cootham canonical: https://www.petrolinadieselcar.co.uk/petrol-in-diesel/cootham-west-sussex/ location: Cootham county: West Sussex latitude: 50.919520 longitude: -0.468960 service: Petrol in a Diesel Car updated: 2026-10-20 --- # Cootham: Petrol in a Diesel Car? How Worried to Be Likely less than you already are — as long as no one has started the car. Till your ignition primes your pump, the starter turns, or your car is driven, petrol in a diesel tank simply sits there and does nothing. Which makes the truthful reply to that first Cootham question — "have I wrecked it?" — usually no. Keep it that way: leave your engine off and call Petrol in Diesel. Below, this page sets out what petrol actually does inside a diesel, how far it may have gone, and how to stop it happening to you again. ## Petrol in a diesel: what does it do to your engine? Passing through a motor, diesel does two jobs at once. Lubricating comes before burning; it does both. Very fine clearances are built into your injectors and the high-pressure fuel pump, and only the diesel running through keeps those surfaces from grinding together. Of these two jobs, petrol handles the first poorly and the second never. It is thinner than diesel and strips away the protection the fuel system depends on, so a pump running on a petrol mixture 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's where the rattling comes from. Put these together and the shape of the issue is clear. It is circulation that causes the harm, not contact. All a tank with petrol in it amounts to is a fuel fault. Whatever a worn pump sheds goes on, carried by the fuel, into your injectors downstream, which is why a pump that has worked on that petrol is where a mechanical problem begins. ## How serious is petrol in a diesel? Four scenarios our engineers see around Cootham Filled up, and never started: no case is better. On a forecourt, and truly only there, the petrol is still limited to that tank — since anywhere else the vehicle was driven to reach it. The job is draining and cleaning on the spot. A brief spell of running, or merely your ignition on. Once primed, the fuel system has drawn petrol out of your tank as far as the filter and the lines. Drain, flush, see to your filter: still usually simple. Your pump has worked a few miles on weakened fuel — that is what driving it meant. The work is the tank, the fuel lines, the fuel filter and clean fuel through the whole system, and how hard your car was driven matters as much as how far. Driving the children to Storrington Primary School is one sort of trip. Very different once more: a trip to Chichester, under 15 miles away, or some miles on the M23, under 25 miles from Cootham, where your engine never stopped running hard. Driven on till it complained — knocking, smoke, a ragged idle, a soft throttle. That's your engine telling you its fuel no longer is acting like diesel. Pull up wherever you are — the verge on Cassidy Place, a lay-by, a side street — and leave the vehicle where it is. A car stopped quickly very rarely has permanent damage, since the fuel drain and the flush, which still come first, deal with it. ## What Cootham 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 will be fine." It will not. Topping up takes out nothing; it gives you a fuller tank of the same mixture. That guidance assumes a diesel fuel system tolerates petrol by percentage. It does not. Myth: "A current diesel can cope with a bit of petrol." If anything, the reverse. Lubrication matters more on modern diesels, not less, because their fuel runs through smaller parts at higher pressure. One myth that catches motorists off guard: if it starts and drives, it must be unharmed. Diesel in a petrol motor generally means a motor that won't run: the motorist stops, and so does the harm. Feed petrol to a diesel and it usually fires up, idles and pulls away as if nothing has happened — all while its pump is wearing. A running engine does not mean fine. An old workaround for a separate issue lies behind this one. Myth: "Add some two-stroke oil and drive it home." It doesn't put back what petrol has diluted, and that petrol is still in the tank later. "Drain it yourself and you are sorted" — a myth, because after it has been running some petrol lies in the filter and lines, waiting to go straight back through the pump on the next start. It's also genuinely dangerous to drain petrol into a can by the roadside. ## Why petrol in a diesel happens so easily On purpose? Never. Through carelessness? Seldom, if ever. One way only, because of the nozzles: the slimmer petrol one slips inside a diesel filler with almost no resistance, whereas the diesel one mostly will not fit a petrol car. That is how the forecourt makes it simple. When routine and your car stop matching, it happens. A new motor, a hire car or a courtesy car. Two motors on one driveway, one petrol, one diesel. A forecourt you know, only with its pumps laid out differently. A train to catch, and a rushed fill en route to Pulborough. Exactly the moment it occurs: after years of driving petrol, a driver fills a diesel Volkswagen Passat for the first time. Your hand repeats what it has always done once you add rain, a phone call or a back seat full of kids. ## How to prevent petrol in a diesel on your next fill-up around Cootham - Read the pump, not the colour. In the UK unleaded handles are usually green and diesel black, yet not on each forecourt. The label is what counts. - Check your filler flap. Plenty of vehicles state the fuel type inside the flap or on the cap. Look at it on the first fill in any motor you don't know. - Mark your key. In a house with one of each, a coloured fob or a sticker on your diesel's key does more than any amount of meaning to remember. - "Diesel", out loud, before you lift the nozzle — each time a new or hired car gets its first tank. It sounds silly. It does the trick. - While you are thinking about something else, this is an easy mistake to make — so put the phone away. - Some diesels have a filler built to block a petrol nozzle, and devices you can add are available for vehicles without one. Such an inhibitor helps up to a point — as a safety net, not a reason to stop reading the pump. - The moment you notice, stop: less petrol in the tank makes a thinner blend. What to do next does not change, though — still don't fire it up. ## Put petrol in a diesel around Cootham already? Short and simple, then, is the order of things. Starting it is out, and so is turning on your ignition. Ask the attendants to help you roll it away from the petrol pump if you're still on the forecourt, whether that's Esso or somewhere else. Next, 0333 366 0103. We will ask what got in, roughly how much, and if it's been run. Corrosion and deposits form the issue with AdBlue, where petrol brings lost protection. So if it was AdBlue, say so — and see its own Cootham page. ## Why one petrol in a diesel task in Cootham costs more than another There is no fair single quote for this, because the four scenarios above are four separate jobs. What moves the cost is mostly which of them you are in. Where the car is matters too, and whether a technician can safely get to it, after the ratio of petrol to what your tank takes. What was put in, how much, and if it has run — three questions we ask before pricing, not after, for precisely that reason. Those replies are what change a range into one firm number. ## About Cootham, briefly Cootham is a village situated in a riverside setting in West Sussex, with an elevation of 34 metres above sea level. Cootham lies near the cities of Chichester and London, being approximately 14.7 and 43.2 miles away respectively. Cootham is characterised by its predominantly detached housing stock and is surrounded by nearby places such as Storrington, Sullington Warren, and Sullington. Cootham has a population of around 1703 residents. ## Fuel drain cover in Cootham and across West Sussex Cootham sits in the RH postcode area, and the vans that answer petrol in diesel call-outs there work the places near it as well — Storrington, Sullington Warren and Sullington among them. You need not bring the car to us. Forecourts, supermarket car parks, lay-bys and your own drive are all spots we drain. ## Still at the pump in Cootham? Then you are in the best spot there can be. Phone, and leave it turned off.