--- title: Kings Hill: Petrol in a Diesel Car, Explained canonical: https://www.petrolinadieselcar.co.uk/petrol-in-diesel/kings-hill-gloucestershire/ location: Kings Hill county: Gloucestershire latitude: 51.711030 longitude: -1.949470 service: Petrol in a Diesel Car updated: 2026-10-01 --- # Kings Hill: Petrol in a Diesel Car? How Worried to Be Less than you likely are, provided it has not been started. Everyone in Kings Hill begins with "have I ruined it?", and the honest answer is normally no: petrol resting in your tank of any diesel stays harmless until priming, cranking or driving draws it into the fuel system. Petrol in Diesel is who to phone, with the motor left off, so it stays that way. Read on for three things: the effect petrol has inside a diesel engine, the signs of how far it has got, and ways to make sure you don't repeat it. ## Inside your engine: what petrol in a diesel does Two jobs fall to diesel on its journey through a motor. It burns, and before it ignites it protects. What stops the surfaces inside the high-pressure pump and your injectors from grinding against one another is your diesel flowing through them — they are built to extremely fine gaps. The second task petrol doesn't do at all, and the first it does badly. Being less viscous than diesel, petrol strips out the protection a fuel system needs, leaving a pump running on that mixture to wear itself. It's also made to resist igniting under compression — the reverse of what a diesel needs — which is why you get the rattling. The shape of the problem is clear once you put those together. It's circulation that causes the damage, not contact. All a tank with petrol in it amounts to is a fuel fault. Whatever a worn pump sheds goes on, carried by your fuel, into the fuel injectors downstream, which is why a pump that has been working on that petrol is where a mechanical problem begins. ## Kings Hill, petrol in a diesel: four situations, from mild to serious Filled up, and not started: no case is better. Being on a forecourt is what makes this the case: elsewhere, the car has been driven there to begin with. With the petrol held in the tank alone, it's drained and cleaned on the spot, and nothing more is needed. Started for a moment, or just the ignition on. Once primed, the fuel system has drawn petrol out of that tank as far as your filter and your lines. Drain, flush, deal with the filter: still normally simple. Some miles driven, and the pump has spent every one of them working on weakened fuel. Miles is only half of that; how hard it was driven matters just as much. Either way the work runs to the tank, the fuel lines, the filter and fresh fuel through the whole system. A school run to Watermoor Church of England Primary School is one matter. Very different a second time: a trip to Gloucester, under 25 miles away, or any miles on the M4, under 15 miles from Kings Hill, where your engine kept running hard. Knocking, a ragged idle, smoke, a throttle gone soft: driven until it complained. That is the motor telling you its fuel has stopped acting like diesel. Stop wherever you are — the verge on North Home Road, a lay-by, a side street — then leave the vehicle where it is. Permanent damage is very uncommon if a vehicle is pulled over early, and the drain and flush-through that still come first take care of it. ## Petrol in a diesel stories Kings Hill motorists hear It will not be fine. The myth: "Fill it the rest of the way with diesel and it will be." A bigger tank of the same mixture is all you get, because topping up removes nothing. Percentage isn't how a diesel fuel system copes with petrol, whatever that advice assumes. Myth: "A newer diesel can cope with a bit of petrol." If anything, the opposite. At higher pressure, through more precise parts: that is how a modern diesel moves its fuel, and so the lubrication counts more, not less. The myth that catches motorists off guard: if it starts and drives, it must be unharmed. The driver of a petrol motor fed diesel usually has no choice but to stop, because it will not run, and the harm stops with them. While your pump grinds, a diesel fed petrol usually starts, ticks over and drives away as if nothing has happened. Fine and running aren't the same at all. Myth: "Add some two-stroke oil and drive the car home." It's an outdated fix for a distinct problem. None of what petrol weakened is put back by it — and afterwards, your tank still contains the petrol. The next start draws petrol back round your pump out of the fuel lines and your filter, where some of that ends up once the engine has been run. That's why a DIY tank drain doesn't sort it — a myth. Also, a can of petrol drained by the roadside is genuinely dangerous. ## How it happens: petrol in a diesel Nobody does it on purpose, and it is seldom carelessness. One way only, because of the nozzles: the slimmer petrol one slips inside a diesel filler with almost no resistance, while the diesel one generally will not fit a petrol vehicle. That is how the forecourt makes it simple. Routine and the car getting out of step is when it takes place. Courtesy car, hire car, or a motor that is brand new. Households running one of each, petrol and diesel. A forecourt you know, but with its pumps arranged differently. Fuelling up in a hurry on the way to Kemble, with a train to catch. The first fill-up in a diesel Volkswagen Passat after years of driving petrol is exactly the moment it occurs. Add a back seat full of children, a phone call or rain, and the hand wins. ## Preventing petrol in a diesel next time you fill up in Kings Hill - Green for unleaded and black for diesel is usual in the UK — but not on each forecourt. Trust the label on the pump, not the colour. - The first fill in a new car is the time to check your filler flap — inside it, or on the cap, many cars state the fuel they take. - Good intentions do less than a sticker or a fob in a bright colour on your diesel's key if a house has one of each. So label it. - Before the nozzle leaves the pump the first time you fill a hired or new vehicle, say "diesel" out loud. Daft, perhaps, but it works. - Mistakes like this are straightforward 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 built to block a petrol nozzle, and aftermarket devices exist for the rest. Count it as a safety net, and keep checking the petrol pump. - As soon as you realise, stop: less petrol inside that tank means a thinner mixture. What to do next doesn't change, though — still do not crank it. ## Put petrol in a diesel in Kings Hill already? Then the order of things is short. Do not fire it up, and don't turn the ignition on. If you're still on the forecourt — Tesco or anywhere else — ask the staff to help you roll it away from the pump. What got in, roughly how much, and if it's run: tell us those when you ring 0333 366 0103. AdBlue, not petrol? Then say so. Corrosion and deposits, not lost protection, make it a different issue — Kings Hill has a page just for it. ## Kings Hill petrol in a diesel tasks: why one costs more than another The four scenarios above are four separate jobs, so no single price for this would be honest. Which of them you're in is mostly what moves your cost. Where your car is matters too, and whether a technician can safely get to it, after the ratio of petrol to what your tank holds. Three questions come first, before quoting, instead of after — what got in, how much, has it run — and that is the reason. A range turns into a straight figure once the answers are in. ## About Kings Hill itself Kings Hill is a suburban area in Gloucestershire, situated near the River Thames, with an elevation of around 121 metres. Kings Hill lies within commuting distance of Gloucester, approximately 16 miles away, and is also within reach of nearby places such as New Mills and Watermoor. Kings Hill has a population of around 4269 people, predominantly living in semi-detached housing. Kings Hill is located in the South West region, about 79 miles west of London. ## Across Gloucestershire and in Kings Hill: fuel drain cover Petrol in diesel call-outs in Kings Hill — part of the GL postcode area — go to teams that also cover the spots round it, New Mills, The Beeches and Watermoor among them. A forecourt, a supermarket car park, a lay-by or your own drive are all spots our engineers drain, and the vehicle does not need to move to us. ## In Kings Hill and still at the petrol pump? The best place there is, then — that's where you are. Keep it off. Ring.