--- title: Explained: Petrol in a Diesel Car Canongate canonical: https://www.petrolinadieselcar.co.uk/petrol-in-diesel/canongate-city-of-edinburgh/ location: Canongate county: City of Edinburgh latitude: 55.951660 longitude: -3.178610 service: Petrol in a Diesel Car updated: 2026-10-19 --- # Should You Worry? Petrol in a Diesel Car in Canongate Less than you probably are, if it has not been started. Petrol sitting in a diesel tank does nothing to the motor till something draws it through the fuel system — your ignition priming your pump, your starter, or the drive on its own. So the fair answer to the first query anyone around Canongate asks, "have I ruined it?", is generally no. Petrol in Diesel is who to phone, with your motor left off, and so it remains that way. The remainder of this page covers what petrol actually does to a diesel, how to tell how far it has got, and how to make sure it does not happen to you a second time. ## Petrol in a diesel: what does it do to the motor? Diesel does two jobs on its way through an engine. It lubricates first, and after that does it burn. Extremely fine clearances are built into the fuel injectors and your high-pressure pump, and just the diesel flowing through keeps their surfaces from grinding together. Of those two tasks, petrol handles the first poorly and the second never. It is thinner than diesel and removes the protection the system hinges on, and so a pump running on a petrol blend 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 is where the knocking comes from. Put these together and the shape of the trouble is clear. The damage is done by circulation, not by contact. Any tank with petrol in it is a fuel issue. After the pump has been working on that petrol, a mechanical problem has started: whatever is shed by a pump that's grinding travels downstream to the injectors with the fuel. ## How serious is petrol in a diesel? Four scenarios our technicians see around Canongate Fuelled up, not once started. The best case there can be. Being on a forecourt is what makes this the case: elsewhere, your car has been driven there to begin with. With the petrol held inside the tank alone, it is drained and rinsed right where it stands, and nothing more is needed. A moment's running, or merely your ignition on. Once primed, the system has pulled petrol from your tank up to the filter and your lines. Still generally simple: drain, flush, and the filter seen to. Driven a few miles. Now your pump has spent those miles labouring on thinned fuel. How hard the car was driven matters as much as how far, and the work takes in your tank, the lines, the fuel filter and clean fuel through the whole circuit. Short trips, like the school run to the local primary school, are one matter. A run as far as Edinburgh, under a mile away, is a very different task. So is any mileage on the M8, under 10 miles from Canongate, where the motor has been working hard the whole time. Driven till it complained. Knocking, a lumpy idle, smoke, a throttle that has gone soft. The motor is telling you the fuel is no longer behaving like diesel. Leave it where it has stopped: a lay-by, a side street, the verge on Canongate. What goes first is still the fuel drain and flush, and that takes care of it, with permanent damage very unusual when a vehicle is stopped early. ## Canongate people and that petrol in a diesel stories they hear Myth: topping up to full with diesel makes it fine. It does not. Nothing comes out when you top up — your tank simply holds more of the same mixture. Percentage isn't how a diesel fuel system tolerates petrol, however much that guidance presumes. "Newer diesels can handle a little petrol" — a myth, and nearer the reverse. At higher pressure, through more precise components: that's how a modern diesel handles its fuel, so the protection matters more, not less. This is the one that fools people. Myth: "If it starts and drives, there is no harm done." Feed diesel to a petrol motor and it normally will not run, so the driver stops — and the harm stops with them. A diesel fed petrol usually starts, ticks over and drives away as if nothing has happened, while your pump grinds. Running isn't the same as fine. An old workaround for a different issue is behind this one. Myth: "Add some two-stroke oil and drive it home." That petrol is still in that tank afterwards, and what it has thinned is not put back. The next start draws petrol back round the pump out of your lines and your filter, where some of it ends up once your engine has run. That is why draining your tank yourself doesn't sort it — a myth. Also, a can of petrol filled at the kerbside is genuinely hazardous. ## Why petrol in a diesel takes place so easily Nobody does it on purpose, and it's seldom carelessness. One way only, because of the nozzles: the slimmer petrol one slides inside a diesel filler with almost no resistance, while the diesel one mostly will not fit a petrol car. That's how the forecourt makes it simple. The moment habit stops matching the car is the moment it takes place. Hire cars, courtesy cars, and cars that are new to you. A household with one petrol and one diesel on the drive. Your ordinary forecourt, its pumps now in a different order. A train to catch, and a hurried fill on the way to Edinburgh Waverley. The first fill-up in a diesel Renault Megane after years of driving petrol is exactly the moment it takes place. The hand repeats what it has always done when you add rain, a phone call or a back seat full of children. ## How to avoid petrol in a diesel at your next fill-up in Canongate - The label is what counts, so check the petrol pump instead of the colour: in the UK unleaded handles are normally green and diesel black, but not on every forecourt. - The first fill in an unfamiliar car is the time to check the filler flap — inside it, or on the cap, plenty of cars state the fuel to use. - Good intentions do less than a sticker or a fob in a vivid colour on the diesel's key if a house has one of each. So mark it. - It sounds daft and it works: on your first fill in a new or hired car, say "diesel" aloud before you take the nozzle off the pump. - Whilst you're thinking about something else, this is an easy mistake to make — so put your phone 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. Treat it as a safety net, and keep checking the pump. - Stop as soon as you realise. Less petrol in that tank makes a weaker mixture. It doesn't change what to do next, which is still not to crank it. ## Put petrol in a diesel around Canongate already? Then the order of things is short. Do not switch the ignition on, and do not fire it up. Ask the staff to help you roll it clear of the petrol pump if you are still on the forecourt, whether that's BP or somewhere else. Then call 0333 366 0103 and tell us what got in, about how much, and whether it's run. Corrosion and deposits are the trouble with AdBlue, where petrol means lost lubrication. So if it was AdBlue, say so — and read its own Canongate page. ## Why one petrol in a diesel task around Canongate costs more than another A fair single quote doesn't exist here: four scenarios, four separate tasks. What shifts your cost is chiefly which of them you are in. The proportion counts next, meaning how much of your tank is petrol, followed by the position of the vehicle and whether getting to it is safe for our van. That's why our engineers ask three questions before costing instead of after: what got in, how much, and whether it's run. A range becomes a straight figure when those replies are in. ## About Canongate, briefly Canongate is a suburban area located on the coast of Scotland, within the City of Edinburgh, and sits at an elevation of 52 metres. Canongate is situated close to the city centre of Edinburgh, approximately 0.4 miles away, and is near other areas such as Calton, Dumbiedykes, and Hillside. Canongate has a population of around 8647 people and predominantly consists of flat-type housing. Canongate is part of the larger Edinburgh urban area, which is 331.3 miles from London. ## Canongate and City of Edinburgh: where our fuel drain cover reaches Canongate rests in the EH postcode area, and our vans that answer petrol in diesel jobs there work the places around it as well — Calton, Dumbiedykes and Hillside among them. The vehicle doesn't need to move to us: our engineers drain at a forecourt, in a supermarket car park, in a lay-by or on your own driveway. ## Still at the pump in Canongate? Nothing beats it: that is where you are. Keep the car turned off, then ring.