--- title: Byfleet: Petrol in a Diesel Car, Explained canonical: https://www.petrolinadieselcar.co.uk/petrol-in-diesel/byfleet-surrey/ location: Byfleet county: Surrey latitude: 51.338400 longitude: -0.473740 service: Petrol in a Diesel Car updated: 2026-10-27 --- # Petrol in a Diesel Car in Byfleet: How Worried Should You Be? If it has not been started, you can worry far less than you likely are. Everyone in Byfleet starts with "have I wrecked it?", and the honest answer is usually no: petrol resting inside your tank of any diesel stays harmless until priming, cranking or driving pulls it into your fuel system. Keep it that way: leave the engine off then call Petrol in Diesel. Read on for three things: the effect petrol has inside a diesel engine, the signs of how far it has got, and the way to make sure you don't do it again. ## What petrol in a diesel does to your engine Two tasks fall to diesel on its route round a motor. It protects to begin with, and only then does it burn. The high-pressure fuel pump and the fuel injectors are designed to extremely fine tolerances, and the diesel passing through them is what keeps those surfaces from grinding against each other. Petrol does the first job poorly and the second not at all. It's runnier than diesel and removes the lubrication your fuel system rests on, and so a pump running on a petrol mix is a pump wearing itself. And petrol is designed to resist igniting under compression, which is the reverse of what a diesel needs from its fuel. That is where the rattling comes from. Put these together and the shape of the problem is plain. It's movement that does the harm, not contact. A tank with petrol in it is a fuel fault. A pump that has been working on that petrol is the beginning of a mechanical one, and whatever a worn pump sheds moves on with the fuel to your injectors further on. ## Byfleet, petrol in a diesel: four cases, from mild to significant Filled up, and never started: no case is better. Being at a forecourt is what makes this possible: elsewhere, the car has been driven there to begin with. With that petrol kept inside that tank alone, it is cleared and rinsed on the spot, and nothing more is needed. A brief spell of running, or merely your ignition on. Petrol has left that tank and got to your filter and the fuel lines, since the system has been primed. Normally little more than clearing, cleaning and seeing to your filter, so still straightforward. Those few miles driven meant the pump working on fuel diluted by petrol the whole way. The work is that tank, the lines, the fuel filter and clean fuel through the entire system, and how hard the car was driven counts as much as how far. Short trips, such as the school run to St Mary's CofE Controlled Primary School, Byfleet, are one thing. Driving as far as Westminster, under 25 miles away, makes a very different job — as does any mileage on the M25, under a mile from Byfleet, with the engine labouring hard the whole time. Driven on till it protested — rattling, smoke, an uneven idle, a soft throttle. The engine is telling you your fuel is no longer behaving like diesel. Pull up where you are — on the verge on The Willows, at the kerb, down a side road — and don't move it. The drain and flush still go first, and they deal with it: when a vehicle is stopped soon, lasting damage is very uncommon. ## Byfleet drivers and that petrol in a diesel myths they hear It will not be fine. The myth: "Fill it the rest of the way with diesel and it will be." A bigger tank of the same mixture is all you get, because topping up removes nothing. Percentage is not how a diesel fuel system copes with petrol, whatever that guidance presumes. If anything, the opposite is true. Myth: "A modern diesel can cope with a bit of petrol." Protection counts more on newer diesels, not less, because their fuel passes through more precise components at higher pressure. The myth that catches motorists out: if it starts and drives, it must be unharmed. The driver of a petrol motor fed diesel usually stops, since it will not run, and the damage stops with them. Whilst your pump grinds, a diesel fed petrol usually starts, ticks over and drives away as if nothing has happened. Fine and running are not the same at all. Not so: a two-stroke additive lets you to drive home. It was an old workaround, meant for another fault. The petrol is still in that tank afterwards, and whatever it has thinned is not put back. The next start draws petrol back round the pump from the fuel lines and the fuel filter, where some of it ends up after the motor has been run. That's why a DIY tank drain doesn't leave you sorted — a myth. It is also really hazardous to drain petrol into a can by the kerbside. ## How petrol ends up: petrol in a diesel A careless moment is seldom the cause, and no one means to do it. A diesel nozzle mostly won't go into a petrol car, yet the slimmer petrol nozzle goes into the filler of a diesel nearly without resistance — so forecourts make this one mistake easy, and just in that direction. Habit and the vehicle getting out of step is how it happens. A new car, a hire car or a courtesy car. Households running one of each, petrol and diesel. The pumps in a different order on a familiar forecourt. A train to catch, and a rushed fill on the way to Byfleet & New Haw. The first fill-up in a diesel Volkswagen Golf after years of driving petrol is precisely the moment it takes place. With rain, a call arriving, or a car full of children to deal with, the hand simply does what it has always done. ## How to avoid petrol in a diesel at your next fill-up in Byfleet - The label is what matters, and so check the pump instead of the colour: in the UK unleaded handles are usually green and diesel black, yet not on each forecourt. - In a motor you do not know, look inside the flap over the filler or at the cap before the first fill: many cars print the fuel there. - Good intentions do less than a sticker or a fob in a vivid colour on your diesel's key when a household has one of each. So label it. - It sounds daft and it does the trick: on the first fill in a new or hired car, say "diesel" aloud before you take the nozzle off the petrol pump. - Mistakes like this are straightforward 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 come with a filler built to refuse a petrol nozzle, and aftermarket devices are available for the remainder. Treat it as a safety net, then keep reading the petrol pump. - Noticing it halfway? Stop at once. A thinner mixture follows from less petrol in the tank, but the next stage remains the same: do not crank it. ## Put petrol in a diesel around Byfleet already? The order of things is brief, then. Starting it is out, and so is turning on your ignition. Yet on the forecourt, at Tesco or anywhere else? Ask the staff to help you roll the vehicle away from the petrol pump. Then phone 0333 366 0103 and tell us what went in, about how much, and whether it's run. AdBlue, not petrol? Then say so. Corrosion and deposits, not lost protection, make it a different fault — Byfleet has a page just for it. ## What makes one Byfleet petrol in a diesel task cost more than the next There is no fair single price for this, since the four scenarios above are four separate tasks. What shifts your cost is chiefly which of them you are in. Next it's the share — how much petrol got in against how much the tank takes — and then where your car is and whether our van can get to it safely. Before any quote, not after, we ask three queries: the fuel that was put in, its volume, and if it has run. That's why. Their replies are what change a range into one firm number. ## About Byfleet Byfleet is a village in Surrey, situated on the River Wey and adjacent to the River Thames, with a low elevation of around 18 metres. Byfleet has a mix of housing types, but semi-detached homes are predominant, and is located near other notable places such as Brooklands and Wisley. Byfleet is also close to West Byfleet, with which it shares some amenities. Byfleet has a population of approximately 4031 residents and is within commuting distance of London, being around 18.9 miles from the city centre. ## Fuel drain cover across Surrey, Byfleet included Petrol in diesel calls in Byfleet — part of the KT postcode area — go to teams that likewise cover the places around it, Brooklands, Wisley and West Byfleet included. Our technicians drain wherever the vehicle is — your own drive, a lay-by, a supermarket car park, a forecourt — so it does not have to come to us. ## At the petrol pump around Byfleet, right now? The best position there is, then — that's where you are. Keep it off. Phone.