--- title: Petrol in a Diesel Car Cuthill — Explained canonical: https://www.petrolinadieselcar.co.uk/petrol-in-diesel/cuthill-east-lothian/ location: Cuthill county: East Lothian latitude: 55.954750 longitude: -2.993980 service: Petrol in a Diesel Car updated: 2026-10-08 --- # Cuthill: Petrol in a Diesel Car? How Worried to Be Likely less than you are now — provided no one has started it. Everyone in Cuthill begins with "have I wrecked it?", and the fair answer is usually no: petrol resting inside the tank of any diesel stays harmless till priming, cranking or driving pulls it into the system. Petrol in Diesel is who to ring, with the engine left off, so it remains that way. Further down, this page sets out what petrol really does inside a diesel, how far it may have gone, and how to stop it happening to you a second time. ## What petrol in a diesel does to the engine Two tasks fall to diesel on its route round a motor. It burns, and before it combusts it protects. Designed to very fine tolerances, the fuel injectors and the pump depend on your diesel flowing through them to stop their surfaces wearing against one another. The second job petrol does not do at all, and the first it does badly. Being less viscous than diesel, petrol strips away the lubrication a fuel system needs, leaving a pump running on the mixture wearing itself. It is equally made to resist igniting under compression — the opposite of what a diesel needs — which is where you get the knocking. The shape of the trouble is clear when you put those together. Not contact but circulation is what does the damage. All a tank with petrol in it amounts to is a fuel issue. A pump that has been running on that petrol is the start of a mechanical one, and whatever a worn pump sheds moves on with your fuel to the injectors further on. ## How serious is petrol in a diesel? Four situations our engineers see in Cuthill The best case there can be: filled up, not once started. Only that tank has petrol in it, and so the task is emptying that tank and purging the system where the vehicle sits. This scenario can only really happen on a forecourt: anywhere else, the vehicle got there by being driven. Started for a second, or only your ignition on. With your system primed, your lines and filter already hold petrol that came from the tank. Normally little more than clearing, flushing and seeing to your filter, and so still easy. Driven a few miles. Now the pump has spent these miles working on weakened fuel. Tank, lines, filter, then fresh fuel put through the entire circuit: that is the work, and the way your car was driven counts as much as the mileage. Driving the kids to the local primary school is one kind of trip. Driving as far as Edinburgh, under 10 miles away, makes a very different job — as does any distance on the M8, under 15 miles from Cuthill, with your engine labouring hard the whole time. Driven on till it protested — rattling, smoke, a lumpy idle, a dead throttle. The motor is telling you the fuel is no longer behaving like diesel. Pull up wherever you are — the verge on Prestongrange Terrace, a lay-by, a side street — then leave the car there. A vehicle stopped quickly very seldom has permanent damage, since the drain and the flush-through, which still come first, sort it out. ## What Cuthill drivers get told about petrol in a diesel — and the myths in it Myth: topping up to full with diesel makes it fine. It doesn't. Topping up takes out nothing; it gives you a bigger tank of the same mixture. The idea behind the advice — that diesel fuel systems accept petrol by percentage — is wrong. Myth: "A current diesel can cope with a bit of petrol." If anything, the reverse. A newer diesel runs its fuel through smaller parts at higher pressure, which makes the lubrication matter more, not less. Myth: "If it starts and drives, there's no harm done." This is the one that fools people. Feed diesel to a petrol engine and it generally will not run, and so the driver stops — and the damage stops with them. While your pump wears, a diesel fed petrol normally starts, ticks over and drives away as if nothing has happened. Being able to run is not the same as being fine. Myth: a two-stroke additive makes it safe to drive home. It is an old fix, supposed for another fault. The petrol is still inside the tank afterwards, and what it has thinned is not put back. The next start draws petrol back round the pump from the lines and the filter, where some of it sits after the motor has been run. That is why a DIY tank drain does not leave you sorted — a myth. Besides, petrol emptied into a can by the road is truly risky. ## How does petrol in a diesel occur? It's seldom carelessness, and no one does it on purpose. The petrol nozzle is the slimmer of the two and slips into a diesel filler with almost no resistance; a diesel nozzle mostly will not go into a petrol car at all. The forecourt makes it easy, and the slip runs one way. The moment habit stops matching your car is the moment it occurs. A new motor, a hire car or a courtesy car. Households running one of each, petrol and diesel. A forecourt you know, only with its pumps laid out differently. A rushed fill en route to Prestonpans with a train to catch. The first fill-up in a diesel Volkswagen Golf after years of driving petrol is precisely the moment it happens. Throw in a back seat full of kids, a phone call or rain, and the hand wins. ## Avoiding petrol in a diesel next time you fill up in Cuthill - Not every forecourt in the UK keeps to green for unleaded and black for diesel, though most generally do. Check the petrol pump's label; the colour is just a clue. - In a vehicle you do not know, look inside the flap over the filler or at the cap before your first fill: plenty of motors print the fuel type there. - A coloured fob or a sticker on your diesel's key achieves more than any amount of intending to remember, in a home with one of each. - It seems daft and it does the trick: on your first fill in a new or hired car, say "diesel" aloud before you take the nozzle off the pump. - While you are thinking about something else, this is an easy mistake to make — so put the phone 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 motors without one. They are a backstop, not a reason to stop reading the pump. - Less petrol means a weaker mixture, so stop as soon as you realise — while remembering that your next step is unchanged. It's still not to start the vehicle. ## Petrol already in a diesel in Cuthill? Start here The order of things is short, then. Don't turn your ignition on, and don't fire it up. If you're still at the forecourt — Thames or anywhere else — ask the staff to help you roll the vehicle clear of the pump. What went in, about how much, and whether it's run: tell us that when you phone 0333 366 0103. Say so if it was AdBlue rather than petrol: it is a separate issue, with its own page for Cuthill, because AdBlue brings corrosion and deposits instead of lost protection. ## One petrol in a diesel job in Cuthill costs more than another. Why? Four different jobs lie behind the four situations above — which is why there is no honest single quote. The scenario itself does most of the work of moving the cost. The ratio matters next, meaning how much of the tank is petrol, followed by the position of the car and whether reaching it is safe for a van. Three questions come first, before quoting, instead of after — what went in, how much, has it run — and that is the reason. A range turns into a straight figure when the answers are in. ## About Cuthill, for a moment Cuthill is a coastal suburban area in East Lothian, situated near the city of Edinburgh and close to the towns of Prestonpans and Preston. Cuthill lies at a low elevation of around 18 metres, with its terraced housing stock reflecting the area's historical development. Cuthill is part of the wider Edinburgh urban area, yet retains a distinct character of its own. ## Fuel drain cover in Cuthill and across East Lothian Cuthill rests in the EH postcode area, and the vans that answer petrol in diesel call-outs there work the places near it as well — Prestonpans, Preston and Dolphingstone among them. The car does not need to move to us: our technicians drain on a forecourt, in a supermarket car park, in a lay-by or on your own drive. ## In Cuthill and still at the petrol pump? Nothing beats it: that is where you now are. Keep the vehicle turned off, then ring.