--- title: Farleigh: Petrol in a Diesel Car, Explained canonical: https://www.petrolinadieselcar.co.uk/petrol-in-diesel/farleigh-somerset/ location: Farleigh county: Somerset latitude: 51.417630 longitude: -2.726830 service: Petrol in a Diesel Car updated: 2026-10-21 --- # Should You Worry? Petrol in a Diesel Car in Farleigh Likely less than you are now — provided no one has started the car. Till the ignition primes the pump, the starter cranks, or your car is driven, petrol in a diesel tank just rests there and does nothing. Which makes the honest reply to the first Farleigh question — "have I ruined it?" — usually no. Leave your motor off and phone Petrol in Diesel — that is how you keep it like that. 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. ## Inside your engine: what petrol in a diesel does On its way through an engine, diesel has two jobs. Before it burns, it protects — and then it ignites. Extremely fine clearances go into the injectors and the high-pressure pump, and just your diesel flowing through stops those surfaces grinding together. Petrol handles the first job poorly and the second not at all. It's runnier than diesel and takes away the protection the fuel system depends on, so a pump running on a petrol mixture 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's where the rattling comes from. Taken together, they show the shape the issue has. The damage is done by movement, not by contact. Petrol in the tank is a fuel problem. Whatever a worn pump sheds goes on, borne by the fuel, into the fuel injectors downstream, which is why a pump that has worked on that petrol is where a mechanical problem begins. ## Four scenarios our technicians see in Farleigh: how bad is petrol in a diesel? Fuelled but never started — the best it gets. That petrol is inside your tank and only the tank, and the job is a drain and a flush where the car sits. This is the one situation that can only really occur on a forecourt, because anywhere else the car has been driven to get there. The ignition switched on, or a short start. With the system primed, the lines and filter now contain petrol that came from that tank. Drain, flush, deal with your filter: still usually simple. Some miles driven, and the pump has spent every one of them running on weakened fuel. The work is that tank, your lines, the fuel filter and clean fuel through the whole system, and how hard the car was driven matters as much as how far. Short trips, such as the school run to Backwell Church of England Junior School, are one thing. Getting as far as Bristol, under 10 miles away, makes a very different job — as does any distance on the M5, under 5 miles from Farleigh, with the motor running hard all the way. It complained, and only then stopped: smoke, clattering, a throttle gone soft, an idle gone uneven. The fuel isn't behaving like diesel any more, and your engine is saying so. Stop wherever you are — the verge on Church Lane, a lay-by, a side street — then leave it where it is. The fuel drain and flush-through still go first, and they deal with it: if a car is pulled over soon, long-term damage is very rare. ## Petrol in a diesel stories Farleigh people hear False: topping up to full with diesel makes it fine. It does not. Topping up takes out nothing; it gives you a fuller tank of the same mixture. A diesel fuel system does not accept petrol by percentage in the way that guidance assumes. Not so: a modern diesel copes with a bit of petrol. Rather, the opposite. At higher pressure, through finer components: that is how a newer diesel handles its fuel, so the lubrication matters more, not less. Myth: "If it starts and drives, there's no harm done." This is the one that fools motorists. Diesel in a petrol motor normally leaves a motor that won't run: the driver stops, and so does the harm. Feed petrol to a diesel and it usually fires up, idles and drives away like nothing happened — all the while its pump is wearing. Fine and running aren't the same at all. "A drop of two-stroke oil and drive it home" — a myth, taken from a fix from years ago, for a separate problem. What petrol has weakened remains weakened, and the petrol remains inside your tank anyway. "Drain it yourself and you're sorted" — a myth, because after it has been running some petrol lies in the filter and lines, ready to go right back through your pump on your next start. Besides, petrol drained into a can by the road is truly dangerous. ## How petrol ends up: petrol in a diesel On purpose? Never. Through carelessness? Rarely, if ever. One way only, since of the nozzles: the narrower petrol one slips inside a diesel filler with almost no resistance, while the diesel one mostly will not fit a petrol motor. That's how the forecourt makes it simple. The moment habit stops matching the car is the moment it happens. Hire cars, courtesy cars, and cars that are new to you. A household with one petrol and one diesel on the drive. Your normal forecourt, its pumps now in a different order. A train to catch, and a hurried fill on the way to Nailsea & Backwell. A new-to-you diesel Volkswagen Passat, its first fuelling, and a driver accustomed to petrol: exactly when it occurs. With rain, a call coming in, or children to deal with, your hand just does what it has always done. ## Avoiding petrol in a diesel next time you fill up in Farleigh - Read the pump, not the colour. In the UK unleaded handles are usually green and diesel black, but not on each forecourt. The label is what matters. - Inspect the filler flap. Plenty of cars state the fuel inside the flap or on the cap. Look at it on your first fill in any car you don't know. - Good intentions count for less than a sticker or a fob in a vivid colour on the diesel's key when a home has one of each. So mark it. - Before the nozzle comes off the pump the first time you fill a hired or new vehicle, say "diesel" aloud. Daft, yes, but it works. - Thinking about something else is when this becomes an easy mistake to make, so tuck your phone away and keep your mind on the petrol pump. - Up to a point, a misfuel inhibitor helps: some diesels have a filler built to block a petrol nozzle, and add-on devices are available for the rest. Treat it as a backstop, then keep reading the pump. - Less petrol means a weaker blend, and so stop the moment you notice — while remembering that your next step is unchanged. It's still not to crank it. ## Already put petrol in a diesel in Farleigh? Short and simple, then, is the order of things. Leave it unstarted, with the ignition switched off as well. The staff at the forecourt — whether at Backwell Motors itself or wherever you filled up — will usually help roll it clear of the petrol pump if you ask. Then phone 0333 366 0103 and tell us what got in, roughly how much, and whether it has run. If it was AdBlue instead of petrol, say so. That is a separate fault — corrosion and deposits and not lost protection — and it has its own page for Farleigh. ## What makes one Farleigh petrol in a diesel task cost more than the next There is no honest single price for this, since the four situations above are four separate tasks. Chiefly, your cost moves with which one you are in. After that it's the proportion — how much petrol got in against how much your tank holds — and then where the vehicle is and whether our van can get to it safely. That's why our engineers ask three questions before costing rather than after: what got in, how much, and if it's run. With those answers, you get a straight figure instead of a range. ## About Farleigh, briefly Farleigh is a small village in Somerset, situated inland at an elevation of 43 metres, approximately 5.9 miles from Bristol. Farleigh has a population of around 574 residents, with predominantly detached housing. Farleigh is close to nearby places such as Backwell Green, Church Town, and Backwell, and is about 112 miles west of London. ## Fuel drain cover across Somerset, Farleigh included Petrol in diesel jobs in Farleigh — part of the BS postcode area — go to vans that likewise cover the locations about it, Backwell Green, Church Town and Backwell included. A forecourt, a supermarket car park, a lay-by or your own drive are all locations we drain, and the car doesn't need to move to us. ## At the petrol pump in Farleigh, still? The best position there is, then — that is where you are. Keep the car turned off, then ring.