--- title: Explained: Petrol in a Diesel Car Slack canonical: https://www.petrolinadieselcar.co.uk/petrol-in-diesel/slack-west-yorkshire/ location: Slack county: West Yorkshire latitude: 53.653660 longitude: -1.874960 service: Petrol in a Diesel Car updated: 2026-10-12 --- # Should You Worry? Petrol in a Diesel Car in Slack Likely less than you are now — provided no one has started it. Petrol sitting in a diesel tank does nothing to your motor till something draws it through the system — the ignition priming your pump, the starter, or the drive on its own. So the truthful answer to the first query everyone in Slack asks, "have I wrecked it?", is usually no. Leave the engine off then call Petrol in Diesel — that keeps it that way. Further down, you will find what petrol actually does inside a diesel, how far it might have got, and how to stop it happening to you a second time. ## Petrol in a diesel: what does it do to the engine? Diesel has two jobs on its way through an engine. It protects to begin with, and only then does it burn. Built to extremely fine tolerances, the injectors and the pump depend on the diesel moving through them to stop their surfaces wearing against one another. Petrol does the first job poorly and the second not at all. It's thinner than diesel and removes the protection the system hinges 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 opposite of what a diesel needs from its fuel. That's where the knocking comes from. Taken together, they show the shape the problem has. Not contact but circulation is what causes the damage. Petrol in the tank is a fuel issue. A pump that has been working on that petrol is the start of a mechanical one, and whatever a worn pump sheds moves on with the fuel to your injectors further on. ## Petrol in a diesel around Slack: how serious is it? Four cases Fuelled, and not started: no case is better. Just that tank has petrol in it, so the job is clearing the tank and rinsing the system where the vehicle sits. This scenario can only truly take place at a forecourt: anywhere else, your car got there by being driven. Started for a second, or only your ignition on. With your system primed, the lines and filter already contain petrol that has come from the tank. Usually little more than clearing, flushing and sorting the fuel filter, and so still simple. Driven a few miles. Now the pump has spent these miles working on thinned fuel. How hard the car was driven counts as much as how far, and this work takes in your tank, your lines, the fuel filter and fresh fuel through the whole system. Driving the kids to Scapegoat Hill Junior and Infant School is one sort of trip. Very different once more: a run to Bradford, under 15 miles away, or any miles on the M62, under a mile from Slack, where the engine kept working hard. Driven till it protested. Rattling, a ragged idle, smoke, a throttle that has gone soft. That's the motor telling you its fuel has stopped behaving like diesel. Pull up on the spot — on the verge on Round Ings Road, at the kerb, down a side road — and do not move it. Lasting damage is very uncommon when a car is stopped quickly, and the drain and flush that still come first take care of it. ## Stories Slack motorists hear about petrol in a diesel Myth: "Fill it the rest of the way with diesel and it'll be fine." It will not. Topping up takes out nothing; it gives you a bigger tank of the same mix. Percentage is not how a diesel fuel system tolerates petrol, whatever that guidance presumes. "Newer diesels can handle a little petrol" — a myth, and closer to the opposite. Lubrication counts more on newer diesels, not less, because their fuel runs through more precise components at higher pressure. Myth: "If it starts and drives, there is no harm done." This is the one that catches motorists. The motorist of a petrol engine fed diesel normally stops, since it will not run, and the harm stops with them. Feed petrol to a diesel and it usually fires up, ticks over and pulls away like nothing has happened — all while its pump wears. Running is not the same as fine. An old fix for a distinct issue is behind this one. Myth: "Add some two-stroke oil and drive the car home." None of what petrol diluted gets put back by it — and afterwards, the tank still contains the petrol. Myth: "Drain the tank yourself and you are sorted." Once the motor has been run, some of that petrol is no longer in your tank: it's in the filter and the lines, and it goes straight back through the pump at the next start. On top of that, petrol drained into a can by the road is genuinely risky. ## How it happens: petrol in a diesel It is rarely carelessness, and no one does it on purpose. One way only, since of the nozzles: the narrower petrol one slips inside a diesel filler with almost no resistance, whereas the diesel one mostly will not fit a petrol vehicle. That's how the forecourt makes it simple. Routine and the car falling out of step is how it occurs. A new vehicle, a hire car or a courtesy car. A household with one petrol and one diesel on the driveway. Your normal forecourt, its pumps suddenly in a different order. Rushing for a train outside Slaithwaite and fuelling up en route. Years of petrol motors behind you, a diesel Volkswagen Golf in front of you at the forecourt for its first tank — that is when. The hand repeats what it has always done once you add rain, a phone call or a back seat full of kids. ## Next time you fill up around Slack: preventing petrol in a diesel - Read the pump, not the colour. In the UK unleaded handles are generally green and diesel black, yet not on every forecourt. The label is what matters. - The first fill in a strange vehicle is the time to check the filler flap — on it, or on the cap, many cars state which fuel to use. - One of each in the household? Label the key to the diesel — a coloured fob, a sticker — because intending to remember is not enough. - Before the nozzle leaves the pump the first time you fill a hired or new car, say "diesel" aloud. Daft, perhaps, but it works. - Whilst you are thinking about something else, this is an easy mistake to make — so tuck the phone away. - A misfuel inhibitor helps, up to a point. Some diesels have a filler built to block a petrol nozzle, and add-on devices are available for cars without one. They are a safety net, not a reason to stop reading the petrol pump. - Noticing it mid-fill? Stop at once. A weaker mix follows from less petrol in the tank, but the next step stays the same: don't crank it. ## Slack: already put petrol in a diesel? Then the order of things is short. Never start the vehicle, and don't turn the ignition on. The staff on the forecourt — whether at Scientific Lubricants itself or wherever you filled up — will normally help push it away from the pump if you ask. Then ring 0333 366 0103 and tell us what went in, about how much, and whether it's run. Corrosion and deposits form the issue with AdBlue, where petrol brings lost protection. So if it was AdBlue, say so — and see its own Slack page. ## One petrol in a diesel task around Slack costs more than another. Why? There is no honest single price for this, because the four scenarios above are four different jobs. What moves your cost is mostly which of them you're in. The ratio counts next, meaning how much of the tank is petrol, and then the position of your car and whether reaching it is safe for our van. That's why our engineers ask three questions before pricing rather than after: what got in, how much, and if it's run. Given those replies, there is a straight figure rather than a range. ## About Slack Slack is a small hamlet situated on the riverside in West Yorkshire, with a elevation of 271 metres. Slack sits near the outskirts of Bradford, approximately 10.7 miles from the city centre, and is surrounded by nearby places such as Outlane, Nettleton Hill, and Outlane Moor. Slack has a population of around 913 people, predominantly living in terraced housing. ## Fuel drain cover across West Yorkshire, Slack included Slack waits in the HD postcode area, and our vans that answer petrol in diesel calls there work the places around it as well — Outlane, Nettleton Hill and Outlane Moor among them. The vehicle 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 driveway. ## Slack: still at the pump? In that case, you couldn't be in a better spot. Turned off it remains; then ring.