--- title: Worried? Petrol in a Diesel Car Hersham canonical: https://www.petrolinadieselcar.co.uk/petrol-in-diesel/hersham-surrey/ location: Hersham county: Surrey latitude: 51.365630 longitude: -0.399400 service: Petrol in a Diesel Car updated: 2026-10-03 --- # Should You Worry? Petrol in a Diesel Car in Hersham Less than you probably are, provided it has not been started. "Have I ruined it?" is the first thing anyone in Hersham asks, and the truthful answer is generally no, because petrol resting in a diesel tank harms nothing till it is dragged through your fuel system — by ignition priming, by your starter, or by being driven. Leave the engine off and ring Petrol in Diesel — that keeps it like that. Below, this page sets out what petrol really does inside a diesel, how far it might have got, and how to stop it happening to you again. ## Inside the engine: what petrol in a diesel does Diesel does two tasks on its way through a motor. Before it combusts, it lubricates — and then it ignites. Extremely fine clearances go into your injectors and your high-pressure pump, and only your diesel flowing through stops their surfaces grinding together. Petrol handles the first job poorly and the second not at all. A pump working on a petrol mix is wearing itself out, since petrol is runnier than diesel and strips out the protection your fuel system depends on. Petrol is also made to resist igniting under compression — the opposite of what a diesel wants from its fuel — and that's where the knocking starts. Taken together, they show the shape the issue takes. It's circulation that does the harm, not contact. Any tank with petrol in it is a fuel issue. Whatever a worn pump sheds travels on, carried by your fuel, into your injectors downstream, which is why a pump that has worked on the petrol is where a mechanical fault begins. ## Four situations our engineers see in Hersham: how bad is petrol in a diesel? Fuelled but never started — as good as it gets. Just that tank has petrol in it, and so the job is emptying the tank and cleaning your system where your car sits. This situation can only truly take place at a forecourt: anywhere else, the vehicle got there by being driven. Ignition on, or started for a moment. The fuel system has been bled, so petrol has left your tank and got to the filter and your lines. Drain, flush, see to your filter: still normally simple. The pump has spent a few miles on thinned fuel — that's what driving the car meant. How hard your car was driven matters as much as how far, and this work covers the tank, the lines, the filter and fresh fuel through the whole circuit. Short trips, such as the school run to Burhill Primary School, are one matter. Driving as far as Westminster, under 25 miles away, makes a very different task — as does any mileage on the M3, under 5 miles from Hersham, with your engine running hard all the way. It complained, and only then stopped: smoke, clattering, a throttle gone soft, an idle gone lumpy. What you are hearing is your motor reporting fuel that no longer behaves like diesel. Stop wherever you are — the verge on Burwood Road, a lay-by, a side street — and leave the car there. A vehicle pulled over soon very rarely has long-term damage, as the fuel drain and the flush, which still go first, take care of it. ## Myths Hersham people hear about petrol in a diesel Myth: topping up to full with diesel makes it fine. It does not. Nothing comes out when you top up — your tank simply holds more of the same mixture. A diesel fuel system doesn't tolerate petrol by percentage in the way that guidance presumes. Myth: "A newer diesel can cope with a bit of petrol." If anything, the reverse. At higher pressure, through more precise parts: that's how a modern diesel handles its fuel, so the lubrication matters more, not less. "It starts, it drives, so no harm done" — the myth that catches more motorists than any other. The driver of a petrol engine fed diesel usually has no choice but to stop, because it will not run, and the damage stops with them. Nothing looks to have happened when a diesel fed petrol fires up, ticks over and drives away, which it usually does; meanwhile the pump grinds. Running is not the same as fine. Not so: a two-stroke additive makes it safe to drive home. It was an old fix, meant for another fault. What petrol has weakened remains weakened, and the petrol remains in the tank anyway. Myth: "Drain that tank yourself and you're sorted." Once your engine has run, some of that petrol is no longer in your tank: it is in your filter and your lines, and it goes straight back through your pump at the next start. Besides, petrol cleared into a can by the road is genuinely dangerous. ## How does petrol in a diesel take place? No one does it on purpose, and it is rarely carelessness. The petrol nozzle is the smaller of the two and slides into a diesel filler with almost no resistance; a diesel nozzle mostly will not go into a petrol vehicle at all. The forecourt makes it easy, and the mistake runs one way. It occurs when routine and your car stop matching. Courtesy car, hire car, or a car that's brand new. Households running one of each, petrol and diesel. Your usual forecourt, its pumps now in a different order. A train to catch, and a rushed fill en route to Walton-On-Thames. The first fill-up in a diesel Nissan Qashqai after years of driving petrol is exactly the moment it takes place. The hand repeats what it has always done when you add rain, a phone call or a back seat full of kids. ## How to prevent petrol in a diesel at your next fill-up around Hersham - Not every forecourt in the UK keeps to green for unleaded and black for diesel, though most generally do. Check the petrol pump's label; the colour is just a clue. - Many vehicles state the fuel type inside the filler flap or on the cap, so check it on the first fill in any vehicle you don't know. - One of each in the home? Mark your key to the diesel — a coloured fob, a sticker — since intending to remember is not enough. - Say it before you lift it. On your first fill in a new or hired car, say "diesel" aloud before you take the nozzle off the pump. It sounds daft and it works. - Mistakes like this are simple to make while your mind is on something else, and so your phone goes away. - Up to a point, a misfuel inhibitor helps: some diesels have a filler built to block a petrol nozzle, and add-on devices exist for the remainder. Count it as a backstop, and keep checking the petrol pump. - Less petrol means a weaker mixture, so stop as soon as you realise — while remembering that your next stage is unchanged. It is still not to start the vehicle. ## Hersham: already put petrol in a diesel? Then the order of things is brief. Do not switch the ignition on, and do not crank it. The attendants at the forecourt — whether at Texaco itself or wherever you filled up — will usually help roll it away from the pump if you ask. Ring 0333 366 0103 next, with three facts — your fuel, the approximate quantity, and if it's run. Corrosion and deposits form the issue with AdBlue, where petrol brings lost protection. So if it was AdBlue, say so — and read its own Hersham page. ## Why one petrol in a diesel job around Hersham costs more than another A fair single price does not exist here: four scenarios, four separate tasks. Mostly, the cost shifts with which situation you are in. Where the vehicle is counts too, and whether a technician can safely reach it, after the proportion of petrol to what your tank holds. Ahead of any quote, not after, come three queries: your fuel that was put in, the amount, and whether it's run. That is why. Their answers are what turn a range into one firm number. ## About Hersham itself Hersham is a village in Surrey, situated on the riverside at an elevation of 19 metres, with semi-detached housing being the predominant type of accommodation. Hersham lies approximately 15 miles from London and is close to nearby places such as West End, Rydens, and Burwood Park. Hersham has a population of around 4535 residents and is located near the city of Westminster. Hersham's riverside setting provides a unique character to the village. ## Fuel drain cover across Surrey, Hersham included Hersham rests in the KT postcode area, and our vans that answer petrol in diesel calls there work the spots near it as well — West End, Rydens and Burwood Park among them. The vehicle does not need to move to us: our technicians drain on a forecourt, in a supermarket car park, in a lay-by or on your own driveway. ## At the pump around Hersham, still? In that case, you could not be in a better position. Turned off it remains; then ring.