--- title: Petrol in a Diesel Car Blackdown — Explained canonical: https://www.petrolinadieselcar.co.uk/petrol-in-diesel/blackdown-devon/ location: Blackdown county: Devon latitude: 50.600920 longitude: -4.116320 service: Petrol in a Diesel Car updated: 2026-10-18 --- # How Worried Should You Be? Petrol in a Diesel Car in Blackdown If it has not been started, worry far less than you probably are. Everyone around Blackdown begins with "have I ruined it?", and the fair answer is normally no: petrol resting in the tank of a diesel stays harmless until priming, cranking or driving pulls it into the system. Petrol in Diesel is who to phone, with your motor left off, and so it stays that way. The remainder of this page explains what petrol really 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. ## Inside the motor: what petrol in a diesel really does Diesel does two jobs on its way through an engine. Lubricating comes before burning; it does both. What keeps the surfaces inside your high-pressure pump and the fuel injectors from wearing down against each other is your diesel passing through them — they are built to very fine gaps. The second task petrol doesn't do at all, and the first it does badly. It's runnier than diesel and strips away the protection your fuel system depends 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 opposite of what a diesel needs from its fuel. That's where the rattling comes from. Combined, those leave the shape of the trouble clear. Contact doesn't do the damage — circulation does. Petrol in the tank is a fuel problem. Once the pump has been labouring on that petrol, a mechanical fault has begun: whatever is shed by a pump that's grinding is carried onward to your injectors with the fuel. ## Blackdown, petrol in a diesel: four situations, from mild to major Fuelled up, not once started. The best case there can be. That petrol is in your tank and just the tank, and the task is a drain and a flush where the car sits. This is the one scenario that can only really take place on a forecourt, as anywhere else your car has been driven to get there. A brief spell of running, or merely the ignition on. With your system primed, the lines and filter now hold petrol that came from your tank. Normally nothing more than emptying, purging and seeing to the fuel filter, and so still easy. Your pump has spent a few miles on diluted fuel — that is what driving the car meant. Tank, lines, filter, then fresh fuel run through the entire circuit: that is this work, and the way the car was driven counts as much as the distance. The school run to Mary Tavy and Brentor Community Primary School is one thing. Very different again: a run to Plymouth, under 25 miles away, or any miles on the M5, under 50 miles from Blackdown, where your engine never stopped labouring hard. Clattering, an uneven idle, smoke, a throttle gone soft: driven till it complained. The engine is telling you your fuel is no longer acting like diesel. Leave it where it has stopped: a lay-by, a side street, the verge on A386. The fuel drain and flush-through still come first, and they deal with it: when a car is stopped early, permanent damage is very rare. ## Blackdown people and that petrol in a diesel myths they hear Myth: "Fill it the rest of the way with diesel and it'll be fine." It will not. A fuller tank of the same mixture is all you get, since topping up takes out nothing. The assumption behind that advice — that diesel fuel systems accept petrol by percentage — is wrong. Myth: a current diesel copes with a bit of petrol. Rather, the reverse. More precise components and higher pressure are how a newer diesel runs its fuel, and that 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. Diesel in a petrol motor usually leaves a motor that will not run: the driver stops, and so does the harm. A diesel fed petrol normally starts, idles and drives away as though nothing has happened, while the pump wears. Being able to run is not proof of being fine. An outdated workaround for a separate problem lies behind this one. Myth: "Add some two-stroke oil and drive the vehicle home." It doesn't put back what petrol has weakened, and the petrol is still in your tank after that. The next start draws petrol back round the pump from your lines and the fuel filter, where some of that ends up once the motor has run. That's why draining the tank yourself does not sort it — a myth. It is also really dangerous to drain petrol into a can by the kerbside. ## Petrol in a diesel: how does it take place? It's rarely carelessness, and no one does it on purpose. A diesel nozzle mostly won't fit a petrol vehicle, yet the smaller petrol nozzle goes into the filler of a diesel nearly without resistance — so forecourts make this one error easy, and just in that direction. It occurs when habit and the vehicle stop matching. A new motor, a hire car or a courtesy car. A household with one petrol and one diesel on the driveway. A forecourt you know, only with its pumps laid out differently. Fuelling up in a hurry on the way to Gunnislake, with a train to catch. A new-to-you diesel Volkswagen Golf, its first fuelling, and a motorist used to petrol: precisely when it occurs. Add rain, a phone call or a back seat full of children, and the hand does what it has always done. ## Next time you fill up in Blackdown: preventing petrol in a diesel - Not every forecourt in the UK keeps to green for unleaded and black for diesel, even if most usually do. Check the pump's label; the colour is just a hint. - In a vehicle you do not know, look inside the flap over your filler or at the cap before your first fill: many cars state the fuel type there. - One of each in the house? Mark your key to your diesel — a coloured fob, a sticker — because intending to remember isn't enough. - It sounds silly and it does the trick: on the first fill in a new or hired car, say "diesel" out loud before you take the nozzle off the petrol pump. - Whilst you're thinking about something else, this is an easy mistake to make — so tuck your phone away. - Add-on devices exist for motors without one, and some diesels are built with a filler that will not accept a petrol nozzle. Useful — but a backstop at best, never a reason to stop checking the label. - The moment you notice, stop: less petrol inside your tank means a thinner blend. What to do next does not change, though — still do not crank it. ## Put petrol in a diesel around Blackdown already? Then the order of things is brief. Starting it is out, and so is turning on the ignition. If you're still at the forecourt — Texaco or anywhere else — ask the staff to help you push it clear of the pump. Next, 0333 366 0103. We will ask what got in, roughly how much, and if it's been run. If it was AdBlue instead of petrol, say so. That is a separate fault — corrosion and deposits rather than lost lubrication — and it has its own page for Blackdown. ## Why one petrol in a diesel task in Blackdown costs more than another A fair single quote doesn't exist here: four situations, four separate tasks. Mostly, the cost moves with which one you're in. Where the vehicle is matters too, and whether a technician can safely get to it, after the ratio of petrol to what your tank holds. That's why our engineers ask three questions before costing rather than after: what went in, how much, and whether it has run. Those answers are what change a range into one firm number. ## About Blackdown, briefly Blackdown is a small suburban area in Devon, situated near the River Tavy and close to the Dartmoor National Park. Blackdown sits at an elevation of 204 metres, overlooking the surrounding countryside. Blackdown is characterized by its predominantly detached housing stock, reflecting its residential nature. Blackdown is located near several nearby places, including Mary Tavy, Kingsett, and West Blackdown, and is approximately 16 miles from Plymouth. ## Fuel drain cover across Devon, Blackdown included Mary Tavy, Kingsett and West Blackdown are among the locations around Blackdown that the same vans work, answering petrol in diesel call-outs across Blackdown's PL postcode area. The car doesn't need to come to us: we drain on a forecourt, in a supermarket car park, in a lay-by or on your own drive. ## Blackdown: still at the petrol pump? The best spot there is, then — that is where you are. Ring, and leave it switched off.