--- title: Explained: Petrol in a Diesel Car North Feltham canonical: https://www.petrolinadieselcar.co.uk/petrol-in-diesel/north-feltham-greater-london/ location: North Feltham county: Greater London latitude: 51.459430 longitude: -0.412170 service: Petrol in a Diesel Car updated: 2026-10-11 --- # How Worried Should You Be? Petrol in a Diesel Car in North Feltham Provided it has not been started, you can worry less than you likely are. "Have I wrecked it?" is the first question everyone around North Feltham asks, and the honest answer is normally no, since petrol resting in a diesel tank harms nothing until it's drawn through the fuel system — by ignition priming, by your starter, or by being driven. Keep it that way: leave your motor off and call Petrol in Diesel. The remainder of this page explains what petrol actually does to a diesel, how to tell how far it has got, and how to make sure it does not happen to you again. ## What petrol in a diesel does to the motor On its way through a motor, diesel does two jobs. It protects to begin with, and after that does it burn. Your high-pressure pump and the fuel injectors are made to very fine tolerances, and the diesel passing through them is what keeps those surfaces from wearing down against each other. The second task petrol doesn't do at all, and the first it does poorly. It's thinner than diesel and takes away the protection the 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 knocking comes from. The shape of the issue is clear once you put those together. Not contact but movement is what does the harm. A tank with petrol in it is a fuel problem. Whatever a worn pump sheds travels on, carried by the fuel, into your injectors further along, which is why a pump that has been working on that petrol is where a mechanical issue starts. ## Petrol in a diesel around North Feltham: how bad is it? Four cases Fuelled, and not started: no case is better. On a forecourt, and truly only there, the petrol is still confined to the tank — since anywhere else your car was driven to get to it. The job is emptying and purging on the spot. Ignition on, or started for a second. Once primed, the fuel system has drawn petrol from the tank as far as the filter and the fuel lines. Usually nothing more than draining, flushing and sorting the fuel filter, so still simple. Those few miles driven meant your pump running on fuel weakened by petrol throughout. The work is your tank, the fuel lines, the fuel filter and fresh fuel through the entire circuit, and how hard the vehicle was driven matters as much as how far. A school run to Sparrow Farm Primary School is one matter. Driving as far as Westminster, under 15 miles away, makes a very different job — as does any mileage on the M4, under 3 miles from North Feltham, with your engine working hard all the way. Driven on till it protested — rattling, smoke, a lumpy idle, a soft throttle. That's your motor telling you its fuel no longer is behaving like diesel. Stop wherever you are — the verge on Faggs Road, a lay-by, a side street — and leave it there. A car stopped early very seldom has permanent damage, since the drain and the flush-through, which still go first, deal with it. ## Myths North Feltham people hear about petrol in a diesel Myth: topping up to full with diesel makes it fine. It doesn't. Topping up takes out nothing; it gives you a bigger tank of the same mixture. Percentage isn't how a diesel fuel system tolerates petrol, whatever that advice assumes. Myth: "A newer diesel can cope with a bit of petrol." If anything, the reverse. A current diesel sends its fuel through finer parts at higher pressure, which makes the protection matter more, not less. This is the one that catches motorists. Myth: "If it starts and drives, there's no damage done." A petrol motor fed diesel generally will not run, and so the driver stops and the damage stops with them. While the pump grinds, a diesel fed petrol normally starts, idles and drives away as though nothing has happened. Running isn't the same as fine. An outdated workaround for a distinct problem is behind this one. Myth: "Add some two-stroke oil and drive it home." None of what petrol thinned is put back by it — and afterwards, your tank still holds the petrol. If the motor has run, part of that petrol sits in your filter and your lines, not your tank — and the next start pulls it right back through the pump. So the myth "drain your tank yourself and you are sorted" does not stand up. Emptying petrol into a can by the roadside is also really risky. ## Why petrol in a diesel happens at all No one does it on purpose, and it's seldom carelessness. A diesel nozzle generally won't go into a petrol car, but the smaller petrol nozzle goes into the filler of a diesel nearly without resistance — so forecourts make this one error straightforward, and only in one direction. The moment routine stops matching the car is the moment it occurs. Hire cars, courtesy cars, and cars that are new to you. A household with one petrol and one diesel on the drive. A well-known forecourt with the pumps in a different order. Fuelling up in a rush on the way to Feltham, with a train to catch. Years of petrol vehicles behind you, a diesel Renault Megane in front of you at the forecourt for its first tank — that is when. Throw in a back seat full of kids, a phone call or rain, and the hand wins. ## Avoiding petrol in a diesel next time you fill up in North Feltham - Read the petrol pump, not the colour. In the UK unleaded handles are usually green and diesel black, but not on every forecourt. The label is what counts. - In a motor you do not know, look inside the flap over your filler or at the cap before your first fill: plenty of motors print the fuel there. - A coloured fob or a sticker on the diesel's key achieves more than any amount of meaning to remember, for a household with one of each. - "Diesel", out loud, before you lift the nozzle — every time a new or hired car gets its first tank. It sounds silly. It does the trick. - Tuck your phone away. This is an easy mistake to make whilst you are thinking about something else. - Some diesels come with a filler built to block a petrol nozzle, and devices you can add exist for vehicles without one. Such an inhibitor helps up to a point — as a safety net, not a reason to stop reading the pump. - Stop as soon as you notice. Less petrol inside that tank makes a weaker mix. It does not change what to do next, which is still not to crank it. ## North Feltham: already put petrol in a diesel? Then the order of things is brief. Leave it unstarted, with your ignition switched off too. If you are still on the forecourt — Tesco or anywhere else — ask the staff to help you roll the car clear of the pump. Call 0333 366 0103 next, with three facts — your fuel, the approximate amount, and whether it's run. If it was AdBlue and not petrol, say so. That is a different problem — corrosion and deposits instead of lost protection — and it has its own page for North Feltham. ## One petrol in a diesel job around North Feltham costs more than another. Why? Four separate tasks lie behind the four scenarios above — which is why there's no fair single quote. Which of them you're in is chiefly what shifts the cost. Two things follow that: the petrol that went in as a share of what the tank holds, then the spot the car is in and whether a van can get to it safely. That is why we ask three questions before pricing rather than after: what went in, how much, and whether it has run. A range turns into a straight figure when the answers are in. ## About North Feltham and its setting North Feltham is a suburban area in the London Borough of Hounslow, situated near the lakes and waterways of the River Crane. North Feltham sits at an elevation of around 23 metres, with semi-detached housing being the predominant type of accommodation. North Feltham is located near several other suburban areas, including Hatton and Feltham, and is close to Hounslow Heath. North Feltham is approximately 12.7 miles from central London, with Westminster being the nearest city centre. ## Fuel drain cover around North Feltham and across Greater London North Feltham waits in the TW postcode area, and the vans that answer petrol in diesel call-outs there work the locations around it as well — Hatton, Feltham and Hounslow Heath among them. The car doesn't need to come to us: our technicians drain on a forecourt, in a supermarket car park, in a lay-by or on your own drive. ## In North Feltham and still at the pump? In that case, you could not be in a better place. Keep it off. Ring.