--- title: Explained: Petrol in a Diesel Car East Molesey canonical: https://www.petrolinadieselcar.co.uk/petrol-in-diesel/east-molesey-surrey/ location: East Molesey county: Surrey latitude: 51.400250 longitude: -0.355050 service: Petrol in a Diesel Car updated: 2026-10-26 --- # East Molesey: Petrol in a Diesel Car? How Worried to Be Not started? Then less worried than you probably feel. Everyone in East Molesey starts with "have I wrecked it?", and the honest answer is normally no: petrol left inside your tank of a diesel remains harmless till priming, cranking or driving draws it into the fuel system. Keep it like that: leave the motor off and ring Petrol in Diesel. What petrol really does to a diesel, how to gauge how far it's travelled, and how to keep it from happening a second time: that's the remainder of this page. ## Petrol in a diesel: what does it do to your engine? Two tasks fall to diesel on its route through a motor. It lubricates first, and after that does it burn. The high-pressure pump and your injectors are made to extremely fine tolerances, and the diesel passing through them is what keeps those surfaces from grinding against one another. Of these two tasks, petrol handles the first badly and the second never. The rattling comes from petrol being designed not to ignite when compressed, which is precisely the reverse of what a diesel needs. On top of that it is runnier than diesel, it strips out the lubrication your system rests on, and any pump working on such a mixture is wearing itself. Combined, those make the shape of the problem plain. It's circulation that does the damage, not contact. Petrol in a tank is a fuel fault. The beginning of a mechanical problem is a pump that has been labouring on that petrol — and whatever a worn pump sheds moves on with your fuel to the injectors downstream. ## Petrol in a diesel in East Molesey: how bad is it? Four cases Fuelled up, never started. The best case there can be. Just that tank has petrol in it, so the job is emptying the tank and rinsing your system where the vehicle stands. This situation can only truly happen at a forecourt: anywhere else, your car got there by being driven. Ignition on, or started for a moment. Once primed, the fuel system has drawn petrol out of that tank up to the fuel filter and the lines. Drain, flush, deal with the fuel filter: still usually simple. Your pump now spent a couple of miles on thinned fuel — that is what driving the car does. Miles is only half of that; how hard it was driven counts just as much. Either way this work runs to the tank, the lines, the fuel filter and fresh fuel through the whole circuit. On the school run to The Orchard Infant School, the miles is small. Any distance on the M3, under 3 miles from East Molesey, means the motor has worked hard throughout, and a run to Westminster, under 15 miles away, is a very different job as well. It protested, and only then stopped: smoke, clattering, a throttle gone soft, an idle gone ragged. The engine is telling you the fuel is no longer acting like diesel. Leave it wherever it stops: a lay-by, a quiet street, the verge on Manor Road. A car stopped quickly very rarely has long-term damage, as the drain and the flush-through, which still go first, deal with it. ## What East Molesey people get told about petrol in a diesel — and the myths in it It will not be fine. The myth: "Fill it the rest of the way with diesel and it'll be." A bigger tank of the same mixture is all it gives, because topping up removes nothing. That guidance presumes a diesel fuel system tolerates petrol by percentage. It doesn't. Myth: "A newer diesel can cope with a bit of petrol." If anything, the reverse. A newer diesel runs its fuel through smaller components at higher pressure, which makes the lubrication matter more, not less. This is the one that catches people. Myth: "If it starts and drives, there's no damage done." The driver of a petrol motor fed diesel normally has no choice but to stop, 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, while the pump grinds. Fine and running aren't the same at all. An outdated workaround for a separate issue lies behind this one. Myth: "Add some two-stroke oil and drive the vehicle home." That petrol is still in that tank afterwards, and whatever it has weakened is not put back. "Drain it yourself and you are sorted" — a myth, since after it has been running some petrol sits in the fuel filter and lines, ready to go right back through the pump on your next start. Draining petrol into a can at the roadside is also truly risky. ## Petrol in a diesel: how does it occur? Nobody does it on purpose, and it is seldom carelessness. 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 easy, and just in one direction. It happens when routine and the car stop matching. A new motor, a hire car or a courtesy car. A household with one petrol and one diesel on the drive. Your ordinary forecourt, its pumps suddenly in a different order. A train to catch, and a hurried fill on the way to Hampton Court. Years of petrol motors behind you, a diesel Renault Clio in front of you at the forecourt for its first tank — that's when. Add a back seat full of kids, a phone call or rain, and habit wins. ## East Molesey motorists: how to avoid petrol in a diesel next time - Not every forecourt in the UK keeps to green for unleaded and black for diesel, though most usually do. Read the petrol pump's label; the colour is just a hint. - Check the filler flap. Many motors state the fuel type inside the flap or on the cap. Look at it on your first fill in a vehicle you do not know. - Label 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. - Say it before you lift it. On your first fill in a new or hired car, say "diesel" out loud before you lift the nozzle off the pump. It sounds daft and it does the trick. - Thinking about something else is when this becomes an easy mistake to make, and so tuck the phone away and keep your mind on the pump. - Add-on devices are available for cars without one, and some diesels are built with a filler that will not accept a petrol nozzle. Useful — but a safety net at best, never a reason to stop checking the label. - As soon as you realise, stop: less petrol inside that tank means a thinner blend. What to do next doesn't change, though — still do not crank it. ## Put petrol in a diesel in East Molesey already? Short and simple, then, is the order of things. Starting it is out, and so is turning on your ignition. Ask the staff to help you roll it away from the petrol pump if you're still on the forecourt, whether that's BP or anywhere else. Next, 0333 366 0103. We'll ask what got in, roughly how much, and if it's been run. Say so if it was AdBlue instead of petrol: it is a different problem, with its own page for East Molesey, since AdBlue brings corrosion and deposits instead of lost protection. ## One petrol in a diesel job around East Molesey costs more than another. Why? The four scenarios above are four separate jobs, so no single price for this would be fair. Chiefly, your cost moves with which situation you are in. The share counts next, meaning how much of your tank is petrol, followed by the location of the car and whether getting to it is safe for a technician. That is why our technicians ask three queries before pricing rather than after: what got in, how much, and if it's run. Those answers change a range into a straight figure. ## About East Molesey, for a moment East Molesey is a village situated on the riverside in Surrey, with a low elevation of around 11 metres above sea level. East Molesey lies close to several notable locations, including Hurst Park and Hampton Court, and is near the neighbouring village of West Molesey. East Molesey has a population of approximately 3670 residents, who mostly live in detached housing. East Molesey is located about 12 miles from central London, with Westminster being the nearest city at a distance of 12.1 miles. ## Fuel drain cover in East Molesey and across Surrey The vans answering petrol in diesel calls in East Molesey, in the KT postcode area, equally work the places near it, Hurst Park, West Molesey and Hampton Court included. The car doesn't need to come to us: our technicians drain at a forecourt, in a supermarket car park, in a lay-by or on your own drive. ## In East Molesey and still at the petrol pump? In that case, you couldn't be in a better place. Leave the vehicle switched off, then ring.