--- title: Petrol in a Diesel Car Clermiston — Explained canonical: https://www.petrolinadieselcar.co.uk/petrol-in-diesel/clermiston-city-of-edinburgh/ location: Clermiston county: City of Edinburgh latitude: 55.955740 longitude: -3.286140 service: Petrol in a Diesel Car updated: 2026-10-16 --- # Petrol in a Diesel Car in Clermiston: How Worried Should You Be? Far less than you probably are, provided it has not been started. Everyone in Clermiston starts with "have I wrecked it?", and the honest answer is usually no: petrol resting inside that tank of any diesel stays harmless till priming, cranking or driving draws it into your fuel system. To leave the car like that, phone Petrol in Diesel and leave your engine switched off. Read on for three things: the effect petrol has inside a diesel engine, the clues of how far it has spread, and the way to make sure you don't do it again. ## Petrol in a diesel: what does it do to the engine? Diesel does two tasks on its way through a motor. Lubricating comes before burning; it does both. What stops the surfaces inside the high-pressure pump and the fuel injectors from grinding against one another is your diesel passing through them — they're built to extremely fine clearances. Of these two tasks, petrol handles the first badly and the second never. The clattering comes from petrol being made not to ignite when compressed, which is exactly the opposite of what a diesel needs. On top of that it is thinner than diesel, it strips away the protection the system depends on, and any pump working on that mix is wearing itself. The shape of the trouble is clear when you put those together. Not contact but movement is what does the harm. All a tank with petrol in it amounts to is a fuel fault. After your pump has been working on that petrol, a mechanical issue has started: anything shed by a pump that is wearing travels downstream to your injectors with the fuel. ## Four situations we see around Clermiston: how bad is petrol in a diesel? Fuelled but not once started — as good as it gets. Being on a forecourt is what makes this possible: elsewhere, the vehicle has been driven there to begin with. With the petrol held inside that tank alone, it is emptied and cleaned on the spot, and nothing more is needed. A brief spell of running, or merely your ignition on. Once primed, the fuel system has pulled petrol out of the tank as far as your filter and your lines. Still usually straightforward: drain, flush, and your filter sorted. Some miles driven, and your pump has spent each of them working on weakened fuel. Distance is only half of that; how hard it was driven counts just as much. Either way the work includes your tank, the fuel lines, the filter and clean fuel through the whole system. Short trips, like the school run to the local primary school, are one matter. Getting as far as Edinburgh, under 5 miles away, makes a very different job — as does any miles on the M8, under 3 miles from Clermiston, with the motor running hard all the way. It protested, and only then stopped: smoke, rattling, a throttle gone soft, an idle gone uneven. The fuel is not acting like diesel any more, and your engine is saying so. Leave it wherever it has stopped: a lay-by, a side street, the verge on Drum Brae Drive. What goes first is still the drain and flush, and that takes care of it, with permanent damage very unusual if a car is stopped early. ## What Clermiston people get told about petrol in a diesel — and the stories in it Myth: topping up to full with diesel makes it fine. It doesn't. A fuller tank of the same mixture is all you get, because topping up takes out nothing. That guidance presumes a diesel fuel system handles petrol by percentage. It doesn't. If anything, the opposite holds. Myth: "A newer diesel can cope with a bit of petrol." A newer diesel sends its fuel through smaller parts at higher pressure, which makes the lubrication count more, not less. The myth that catches people off guard: if it starts and drives, it must be unharmed. Diesel in a petrol motor normally leaves a motor that will not run: the motorist stops, and so does the harm. Feed petrol to a diesel and it normally starts, idles and drives away like nothing has happened — all the while its pump wears. A running engine does not mean fine. "A drop of two-stroke oil and drive it home" — a myth, borrowed from a fix from years ago, for a different problem. What petrol has weakened remains thinned, and the petrol remains inside the tank regardless. "Drain it yourself and you are sorted" — a myth, because after it has been running some petrol sits in your filter and lines, ready to go straight back through your pump at your next start. Draining petrol into a can by the roadside is also truly dangerous. ## Why petrol in a diesel happens at all Carelessness is seldom the cause, and no one means to do it. The forecourt makes it easy: the petrol nozzle is the smaller of the two, and it slides into a diesel filler with almost no resistance, whilst a diesel nozzle mostly will not go into a petrol car at all. So the slip runs one way. The moment habit stops matching your car is the moment it takes place. A new vehicle, a hire car or a courtesy car. One petrol and one diesel on the driveway of the same household. Your ordinary forecourt, its pumps now in a different order. A train to catch, and a rushed fill en route to South Gyle. Years of petrol cars behind you, a diesel Renault Megane in front of you at the forecourt for its first tank — that's when. With rain, a call coming in, or a car full of children to deal with, the hand simply does what it always has. ## Clermiston people: how to prevent petrol in a diesel next time - Check the petrol pump, not the colour. In the UK unleaded handles are normally green and diesel black, yet not on each forecourt. The label is what counts. - Inspect your filler flap. Plenty of vehicles state the fuel inside the flap or on the cap. Look at it on your first fill in a 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 intending to remember. - Before the nozzle comes off the pump the first time you fill a hired or new vehicle, say "diesel" aloud. Daft, yes, yet it does the trick. - Mistakes like this are simple to make while your mind is on something else, so your phone goes away. - A misfuel inhibitor helps, up to a point. Some diesels come with a filler built to reject a petrol nozzle, and add-on devices exist for cars without one. They are a safety net, not a reason to stop reading the petrol pump. - The moment you realise, stop: less petrol inside the tank means a weaker mix. What to do next doesn't change, though — still do not fire it up. ## Clermiston: already put petrol in a diesel? The order of things is short, then. Leave it unstarted, with your ignition switched off too. Still on the forecourt, at Shell or anywhere else? Ask the staff to help you push the car away from the petrol pump. Then ring 0333 366 0103 and tell us what went in, about how much, and if it has run. If it was AdBlue and not petrol, say so. That is a separate fault — corrosion and deposits and not lost protection — and it has its own page for Clermiston. ## Clermiston petrol in a diesel tasks: why one costs more than another An honest single price doesn't exist here: four situations, four separate jobs. The scenario itself does most of the work of moving the cost. Two things come after that: the petrol that went in as a share of what the tank takes, then the place the car is in and whether a technician can reach it safely. That is why we ask three questions before costing rather than after: what got in, how much, and whether it has run. With the replies, you get a straight figure rather than a range. ## About Clermiston itself Clermiston is a suburban area in the City of Edinburgh, situated approximately 3.8 miles west of Edinburgh's city centre. Clermiston occupies a coastal setting, with its elevation at around 80 metres above sea level. Clermiston is characterised by its predominant housing type, which is mainly flat. Clermiston is close to nearby places such as Drumbrae, Bughtlin, and Davidsons Mains. ## Clermiston and City of Edinburgh: where our fuel drain cover reaches Petrol in diesel calls in Clermiston — part of the EH postcode area — go to vans that also cover the locations around it, Drumbrae, Bughtlin and Davidsons Mains included. Our technicians drain where the car is — your own drive, a lay-by, a supermarket car park, a forecourt — so it does not have to come to us. ## Still at the pump around Clermiston? The best position there is, then — that's where you are. Leave the car switched off, then ring.