--- title: Worried? Petrol in a Diesel Car Errol canonical: https://www.petrolinadieselcar.co.uk/petrol-in-diesel/errol-perth-and-kinross/ location: Errol county: Perth and Kinross latitude: 56.392370 longitude: -3.212590 service: Petrol in a Diesel Car updated: 2026-10-03 --- # Errol: Petrol in a Diesel Car? How Worried to Be Less than you probably are, if it hasn't been started. Petrol sitting in a diesel tank does nothing to the engine till something draws it through your fuel system — your ignition priming the pump, the starter, or driving itself. So the truthful answer to the first question everyone in Errol asks, "have I wrecked it?", is generally no. Leave the engine off and ring Petrol in Diesel — that is how you keep it that way. What petrol really does to a diesel, how to gauge how far it has gone, and how to keep it from happening again: that's the remainder of this page. ## Inside the motor: what petrol in a diesel really does Passing through an engine, diesel is doing two things at once. It ignites, and before it ignites it protects. Built to extremely fine gaps, the fuel injectors and the pump depend on the diesel moving through them to keep their surfaces from wearing against one another. The second task petrol doesn't do at all, and the first it does badly. The rattling comes from petrol being designed not to ignite when compressed, which is exactly the opposite of what a diesel needs. On top of that it is thinner than diesel, it strips out the protection the fuel system rests on, and any pump working on that mix is wearing itself. Seen together, they make clear the shape the trouble takes. It's circulation that does the harm, not contact. All a tank with petrol in it amounts to is a fuel problem. After the pump has been labouring on that petrol, a mechanical fault has started: whatever is shed by a pump that's grinding travels onward to the injectors with your fuel. ## Errol, petrol in a diesel: four situations, from mild to serious Filled up, and not started: nothing beats it. Only the tank has petrol in it, so the job is clearing your tank and rinsing the fuel system where the vehicle sits. This situation can only truly happen on a forecourt: anywhere else, the vehicle got there by being driven. Started for a second, or only the ignition on. With your system primed, the lines and filter already hold petrol that came from that tank. That's usually still an easy task — a drain, a flush, and the fuel filter seen to. Driven a couple of miles. Now your pump has spent those miles running on weakened fuel. The work is that tank, your lines, the filter and clean fuel through the whole circuit, and how hard your car was driven counts as much as how far. Short trips, like the school run to the local primary school, are one thing. A run as far as Perth, under 10 miles away, is a very different task. So is any mileage on the M90, under 10 miles from Errol, where the motor has been labouring hard the whole time. Driven on till it complained — knocking, smoke, a lumpy idle, a dead throttle. What you are hearing is the motor signalling fuel that no longer runs like diesel. Pull up where you are — on the verge on Church Avenue, at the kerb, down a side road — and don't move it. What goes first is still the fuel drain and flush, and that sorts it out, with lasting damage very uncommon when a car is stopped early. ## Stories Errol people hear about petrol in a diesel False: topping up to full with diesel makes it fine. It doesn't. A fuller tank of the same mixture is all you get, because topping up takes out 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 opposite. Smaller components and higher pressure are the way a modern diesel runs its fuel, and that makes the protection matter more, not less. One myth that catches people off guard: if it starts and drives, it must be unharmed. A petrol motor fed diesel normally will not run, and so the motorist stops and the harm stops with them. A diesel fed petrol generally starts, idles and drives away as though nothing has happened, while the pump wears. Running doesn't mean fine. "A drop of two-stroke oil and drive it home" — a myth, taken from a fix from years ago, for a distinct fault. It doesn't put back what petrol has thinned, and the petrol is still inside that tank later. Once your engine has been run, part of that petrol sits in the fuel filter and the fuel lines, not the tank — and your next start pulls it straight back through the pump. So the myth "drain that tank yourself and you're sorted" does not stand up. And, a can of petrol filled by the roadside is truly dangerous. ## How it happens: petrol in a diesel No one does it on purpose, and it's seldom carelessness. The petrol nozzle is the narrower of the two and slips into a diesel filler with almost no resistance; a diesel nozzle mostly will not go into a petrol motor at all. The forecourt makes it simple, and the error runs one way. It happens when habit and your car stop matching. Hire cars, courtesy cars, and vehicles that are new to you. One petrol and one diesel on the driveway of the same household. Your ordinary forecourt, its pumps now in a different order. A train to catch, and a hurried fill en route to Invergowrie. The first fill-up in a diesel Renault Clio after years of driving petrol is exactly the moment it takes place. With rain, a call coming in, or a car full of children to deal with, your hand just does what it has always done. ## Next time you fill up around Errol: preventing petrol in a diesel - Not every forecourt in the UK follows green for unleaded and black for diesel, even if most generally do. Check the petrol pump's label; the colour is just a clue. - Check your filler flap. Plenty of motors state the fuel type inside the flap or on the cap. Look at it on the first fill in a car you don't know. - A coloured fob or a sticker on the diesel's key achieves more than any amount of intending to remember, for a house with one of each. - Say it before you lift it. On your first fill in a new or hired car, say "diesel" out loud before you take the nozzle off the petrol pump. It sounds silly and it does the trick. - While you are thinking about something else, this is an easy mistake to make — so put your phone away. - A misfuel inhibitor helps, up to a point. Some diesels come with a filler built to refuse a petrol nozzle, and add-on devices exist for motors without one. They are a backstop, not a reason to stop checking the pump. - Spotting it halfway? Stop there and then. A weaker mixture follows from less petrol in the tank, but your next stage remains the same: do not crank it. ## Errol: already put petrol in a diesel? Then, there is just a short order of things. Starting it is out, and so is turning on the ignition. If you're still at the forecourt — Shell or anywhere else — ask the staff to help you roll the vehicle clear of the pump. Then ring 0333 366 0103 and tell us what was put in, about how much, and whether it's run. Corrosion and deposits form the problem with AdBlue, where petrol brings lost protection. So if it was AdBlue, say so — and see its own Errol page. ## Errol petrol in a diesel tasks: why one costs more than another A fair single quote does not exist here: four scenarios, four separate tasks. Mostly, your cost moves with which situation you're in. The ratio counts next, meaning how much of that tank is petrol, and then the location of the vehicle and whether reaching it is safe for a technician. Three queries come first, before any quote, rather than after — what went in, how much, has it run — and this is the reason. A range becomes a straight figure once those answers are in. ## About Errol itself Errol is a coastal village in Perth and Kinross, situated near the Firth of Tay at an elevation of 36 metres. Errol lies approximately 8.7 miles from Perth and is surrounded by nearby places such as Grange and Leetown. Errol has a population of around 1504 people and predominantly features detached housing. Errol is located in a scenic area, with the city of Perth and its amenities within easy reach. ## Fuel drain cover across Perth and Kinross, Errol included Our teams answering petrol in diesel call-outs in Errol, in the PH postcode area, also work the locations around it, Grange, Grange Park and Leetown among them. You need not bring the vehicle to us. Forecourts, supermarket car parks, lay-bys and your own driveway are all locations we drain. ## Errol: still at the pump? The best place there is, then — that's where you are. Turned off it stays; then ring.