--- title: Thurlestone: Petrol in a Diesel Car, Explained canonical: https://www.petrolinadieselcar.co.uk/petrol-in-diesel/thurlestone-devon/ location: Thurlestone county: Devon latitude: 50.270450 longitude: -3.862890 service: Petrol in a Diesel Car updated: 2026-10-21 --- # How Worried Should You Be? Petrol in a Diesel Car in Thurlestone Provided it hasn't been started, worry less than you likely are. Everyone in Thurlestone begins with "have I wrecked it?", and the fair answer is normally no: petrol resting in that tank of a diesel remains harmless until priming, cranking or driving pulls it into your fuel system. Keep it like that: leave your engine off and ring Petrol in Diesel. The rest of this page explains what petrol actually does to a diesel, how to judge how far it has got, and how to make sure it doesn't happen to you again. ## What petrol in a diesel does to the engine Diesel has two jobs on its way through an engine. Before it ignites, it lubricates — and then it burns. The high-pressure pump and the fuel injectors are designed to very fine tolerances, and the diesel passing through them is what stops those surfaces from grinding against one another. Petrol handles the first task badly and the second not at all. It's runnier than diesel and takes away the lubrication your fuel system rests on, and so a pump running on a petrol mix 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 is where the knocking comes from. The shape of the issue is clear once you put those together. Contact does not do the harm — movement does. Petrol in a tank is a fuel problem. Whatever a worn pump sheds travels on, borne by the fuel, into the injectors downstream, which is why a pump that has been working on the petrol is where a mechanical issue begins. ## Petrol in a diesel in Thurlestone: how serious is it? Four situations Filled up, never started. The best case there can be. Just that tank has petrol in it, and so the job is clearing that tank and cleaning your system where the car stands. This situation can only really take place at a forecourt: anywhere else, your car got there by being driven. A moment's running, or just your ignition on. The fuel system has been primed, and so petrol has left the tank and got to your filter and your lines. That is usually still an easy task — a drain, a flush, and the filter dealt with. The pump now spent a couple of miles on weakened fuel — that's what driving it does. The work is that tank, the fuel lines, the filter and fresh fuel through the entire circuit, and how hard the vehicle was driven matters as much as how far. Short trips, like the school run to Thurlestone All Saints Church of England Academy, are one thing. A run as far as Plymouth, under 15 miles away, is a very different task. So is any miles on the M5, under 50 miles from Thurlestone, where your engine has been labouring hard throughout. Driven until it protested. Clattering, a ragged idle, smoke, a throttle that has gone soft. The fuel is not acting like diesel any more, and the engine is saying so. Stop on the spot — on the verge on Eddystone Road, at the kerb, down a side road — and do not move it. Long-term damage is very rare when a vehicle is pulled over early, and the drain and flush-through that still go first sort it out. ## Myths Thurlestone motorists hear about petrol in a diesel Myth: "Fill it the rest of the way with diesel and it'll be fine." It will not. Nothing comes out when you top up — the tank just holds more of the same mixture. A diesel fuel system does not tolerate petrol by percentage in the way that advice supposes. If anything, the opposite holds. Myth: "A newer diesel can cope with a bit of petrol." Smaller parts and higher pressure are the way a modern diesel runs its fuel, and that makes the lubrication matter more, not less. One myth that catches drivers out: if it starts and drives, it must be unharmed. Feed diesel to a petrol engine and it generally won't run, so the driver stops — and the harm stops with them. Nothing looks to have happened when a diesel fed petrol fires up, ticks over and drives away, as it usually will; meanwhile your pump wears. Being able to run is not the same as being fine. An old fix for a distinct fault lies behind this one. Myth: "Add some two-stroke oil and drive the car home." That petrol is still in your tank afterwards, and what it has thinned isn't put back. "Drain it yourself and you're sorted" — a myth, because after it has been running some petrol sits in the fuel filter and lines, ready to go right back through the pump on the next start. And, a can of petrol filled by the kerbside is truly dangerous. ## How petrol ends up: petrol in a diesel It's seldom carelessness, and nobody does it on purpose. A diesel nozzle generally won't go into a petrol motor, but the narrower petrol nozzle goes into the filler of a diesel almost without resistance — so forecourts make this one error simple, and just in that direction. Routine and the car falling out of step is how it happens. A new car, a hire car or a courtesy car. One petrol and one diesel on the drive of the same household. Your ordinary forecourt, its pumps suddenly in a different order. A rushed fill en route to Ivybridge with a train to catch. Years of petrol vehicles behind you, a diesel Volkswagen Golf in front of you on the forecourt for its first tank — that's when. Throw in a back seat full of kids, a phone call or rain, and habit takes over. ## Next time you fill up in Thurlestone: preventing petrol in a diesel - Not every forecourt in the UK keeps to green for unleaded and black for diesel, even if most generally do. Read the pump's label; the colour is just a hint. - Inspect the filler flap. Plenty of cars state the fuel type inside the flap or on the cap. Look at it on your first fill in any car you do not know. - A coloured fob or a sticker on the diesel's key achieves more than any amount of intending to remember, in a household with one of each. - It seems silly and it does the trick: on your first fill in a new or hired car, say "diesel" out loud before you lift the nozzle off the petrol pump. - Thinking about something else is when this becomes an easy mistake to make, and so tuck your phone away then keep your mind on the petrol pump. - Add-on devices exist for motors without one, and some diesels come with a filler that won't take a petrol nozzle. Useful — but a safety net only, never a reason to stop checking the label. - Noticing it mid-fill? Stop there and then. A weaker mix follows from less petrol inside your tank, yet the next stage stays the same: do not crank it. ## Already put petrol in a diesel around Thurlestone? The order of things is brief, then. Do not switch your ignition on, and don't crank it. If you are still on the forecourt — Asda Express or anywhere else — ask the staff to help you push the vehicle clear of the petrol pump. What went in, about how much, and if it's run: tell us that when you phone 0333 366 0103. Corrosion and deposits form the problem with AdBlue, where petrol means lost lubrication. So if it was AdBlue, say so — and read its own Thurlestone page. ## Why one petrol in a diesel job around Thurlestone costs more than another The four scenarios above are four separate jobs, so no single price for this would be fair. The situation itself does most of the work of moving the cost. Where your car is matters too, and whether a van can safely reach it, after the ratio of petrol to what your tank holds. That is why our engineers ask three queries before pricing rather than after: what was put in, how much, and if it's run. Those replies change a range into a straight figure. ## About Thurlestone Thurlestone is a small coastal village in Devon, situated near the towns of Bantham and Buckland, with South Milton to the north. Thurlestone sits at an elevation of 41 metres, overlooking the sea and surrounded by rolling hills. Thurlestone has a population of around 566 people, predominantly living in detached houses. Thurlestone is located 14.1 miles from Plymouth and 183.8 miles from London. ## Across Devon and in Thurlestone: fuel drain cover Petrol in diesel call-outs around Thurlestone — part of the TQ postcode area — go to vans that also cover the spots round it, Bantham, Buckland and South Milton among them. You need not bring the car to us. Forecourts, supermarket car parks, lay-bys and your own drive are all spots we drain. ## Still at the pump around Thurlestone? Then, you couldn't be in a better place. Leave the car switched off, then ring.