--- title: Explained: Petrol in a Diesel Car Bermondsey canonical: https://www.petrolinadieselcar.co.uk/petrol-in-diesel/bermondsey-greater-london/ location: Bermondsey county: Greater London latitude: 51.495000 longitude: -0.076470 service: Petrol in a Diesel Car updated: 2026-10-28 --- # Should You Worry? Petrol in a Diesel Car in Bermondsey Far less than you probably are, provided it hasn't been started. Petrol sitting in a diesel tank does nothing to your motor until something pulls it through the fuel system — the ignition priming the pump, the starter, or the drive itself. So the truthful answer to the first question everyone around Bermondsey asks, "have I ruined it?", is normally no. To leave it like that, phone Petrol in Diesel then leave your engine alone. The remainder of this page sets out what petrol actually does to a diesel, how to judge how far it has got, and how to make sure it does not happen to you again. ## Your engine and petrol in a diesel: what happens Diesel has two tasks on its way through an engine. Before it ignites, it lubricates — and then it ignites. Very fine tolerances are built into your injectors and your high-pressure pump, and just your diesel running through stops those surfaces grinding together. Badly at the first, not at all at the second: that's petrol. Being less viscous than diesel, petrol strips out the protection a fuel system needs, so a pump on that mixture wearing itself. It's equally made to resist igniting under compression — the reverse of what a diesel needs — which is where you hear the knocking. Put those together and the shape of the issue is clear. Not contact but circulation is what causes the damage. Petrol in the tank is a fuel issue. The start of a mechanical one is a pump that has been working on that petrol — and whatever a worn pump sheds moves on with the fuel to your injectors beyond it. ## How bad is petrol in a diesel? Four scenarios our engineers see around Bermondsey Filled up, and not started: nothing beats it. Only the tank has petrol in it, and so the job is draining that tank and flushing your system where the car sits. This situation can only truly take place on a forecourt: anywhere else, the car got there by being driven. Your ignition turned on, or a brief start. Once primed, your system has drawn petrol from that tank up to your filter and the fuel lines. That's usually still an easy job — a drain, a flush, and the fuel filter dealt with. Driven a few miles. Now your pump has spent these miles labouring on thinned fuel. How hard your car was driven counts as much as how far, and the work covers your tank, the lines, your filter and clean fuel through the whole system. On the school run to Boutcher Church of England Primary School, the distance is small. A run as far as London, under 3 miles away, is a very different job. So is any miles on the M11, under 10 miles from Bermondsey, where the engine has been labouring hard the whole time. It protested, and only then stopped: smoke, knocking, a throttle gone soft, an idle gone ragged. The fuel isn't behaving like diesel any more, and the engine is telling you. Leave it wherever it stops: a lay-by, a quiet street, the verge on Bacon Grove. What goes first is still the fuel drain and flush, and that sorts it out, with lasting damage very rare when a vehicle is pulled over quickly. ## Petrol in a diesel stories Bermondsey people hear Myth: "Fill it the rest of the way with diesel and it'll be fine." It will not. Nothing is removed when you top up — your tank simply carries more of the same mixture. A diesel fuel system doesn't accept petrol by percentage in the way that advice supposes. Not so: a newer diesel copes with a bit of petrol. If anything, the opposite. Lubrication matters more on current diesels, not less, since their fuel passes through smaller components at higher pressure. "It starts, it drives, so there is no harm" — the myth that catches most drivers than any other. The motorist of a petrol engine fed diesel usually stops, since it will not run, and the damage stops with them. A diesel fed petrol usually starts, idles and drives away as if nothing has happened, whilst your pump wears. Fine and running are not the same thing. An old fix for a distinct issue lies behind this one. Myth: "Add some two-stroke oil and drive the car home." It does not put back what petrol has thinned, and the petrol is still inside your tank later on. The next start draws petrol back round your pump out of the fuel lines and your filter, where some of that sits once the motor has been run. That's why draining the tank yourself does not sort it — a myth. Also, a can of petrol drained by the roadside is truly hazardous. ## How petrol ends up: petrol in a diesel Carelessness is seldom the cause, and no one means to do it. A diesel nozzle generally won't go into a petrol vehicle, but the narrower petrol nozzle goes into the filler of a diesel almost without resistance — so forecourts make this one mistake easy, and only in one direction. The moment routine stops matching your car is the moment it occurs. A new car, a hire car or a courtesy car. A household with one petrol and one diesel on the driveway. Your normal forecourt, its pumps suddenly in a different order. A train to catch, and a rushed fill on the way to London Bridge. The first fill-up in a diesel Volkswagen Golf after years of driving petrol is exactly the moment it happens. Add rain, a phone call or a back seat full of children, and the hand does what it has always done. ## Preventing petrol in a diesel next time you fill up in Bermondsey - Read the petrol pump, not the colour. In the UK unleaded handles are usually green and diesel black, yet not on every forecourt. The label is what counts. - The first fill in an unfamiliar motor is the time to check your filler flap — inside it, or on the cap, many cars state which fuel to use. - Mark your key. In a house with one of each, a coloured fob or a sticker on the diesel's key does more than any amount of meaning to remember. - "Diesel", out loud, before you lift the nozzle — every time a new or hired car needs its first tank. It seems silly. It works. - Put your phone away. This is an easy mistake to make while you're thinking about something else. - A misfuel inhibitor helps, up to a point. Some diesels have a filler designed to refuse a petrol nozzle, and add-on devices exist for vehicles without one. They are a backstop, not a reason to stop reading the petrol pump. - As soon as you realise, stop: less petrol in your tank makes a thinner mixture. What to do next doesn't change, though — still do not start the vehicle. ## Put petrol in a diesel in Bermondsey already? Then the order of things is short. Starting it is out, and so is switching on your ignition. The staff at the forecourt — whether at Tesco itself or wherever you filled up — will usually help push it away from the pump if you ask. Then phone 0333 366 0103 and tell us what went in, roughly how much, and whether it has run. If it was AdBlue instead of petrol, say so. That is a different issue — corrosion and deposits and not lost lubrication — and it has its own page for Bermondsey. ## What makes one Bermondsey petrol in a diesel task cost more than the next There is no fair single price for this, because the four situations above are four different tasks. What moves the cost is mostly which of them you're in. The share matters next, meaning how much of that tank is petrol, followed by the position of the vehicle and whether getting to it is safe for our van. That is why our engineers ask three queries before costing instead of after: what got in, how much, and whether it's run. Their answers are what turn a range into one firm number. ## About Bermondsey, briefly Bermondsey is a locality in south London, situated on the River Thames at an elevation of around 4 metres. Bermondsey sits close to the city centre, approximately 2.4 miles from central London, and is near other areas such as Walworth and Tower Hill. Bermondsey is predominantly composed of flat dwellings, reflecting its urban character. Bermondsey has a population of around 11964 people, according to recent estimates. ## Across Greater London and around Bermondsey: fuel drain cover Walworth, Tower Hill and The Borough are among the spots around Bermondsey that the same teams work, answering petrol in diesel jobs across Bermondsey's SE postcode area. We drain wherever your car is — your own drive, a lay-by, a supermarket car park, a forecourt — so it never needs to come to us. ## At the pump around Bermondsey, right now? The best position there is, then — that's where you are. Keep the vehicle turned off, then ring.