Coplandhill: Petrol in a Diesel Car? How Worried to Be
Far less than you probably are, if it has not been started. Everyone around Coplandhill begins with "have I ruined it?", and the fair answer is generally no: petrol left in the tank of a diesel stays harmless until priming, cranking or driving pulls it into the fuel system. To keep the vehicle that way, ring Petrol in Diesel and leave the motor switched off. What petrol really does to a diesel, how to judge how far it's travelled, and how to stop it from happening a second time: that's the remainder of this page.
Inside the engine: what petrol in a diesel really does
Diesel has two tasks on its way through an engine. Before it combusts, it protects — then it ignites. Your high-pressure pump and the injectors are made to extremely fine tolerances, and the diesel passing through them is what keeps those surfaces from grinding against one another.
Of these two tasks, petrol manages the first badly and the second not at all. The knocking comes from petrol being designed not to ignite when compressed, which is precisely the opposite of what a diesel needs. On top of that it is thinner than diesel, it strips out the protection the fuel system depends on, and any pump working on that blend is wearing itself.
Together, those leave the shape of the issue clear. The harm is done by movement, not by contact. Any tank with petrol in it is a fuel issue. A pump that has been labouring on that petrol is the beginning of a mechanical one, and whatever a worn pump sheds travels on with the fuel to your injectors downstream.
How bad is petrol in a diesel? Four situations our engineers see around Coplandhill
Filled up, and not started: no case is better. That petrol is inside your tank and just the tank, and the task is a drain and a flush where your car sits. This is the one situation that can only truly occur on a forecourt, because anywhere else the vehicle has been driven to get there.
Started for a moment, or just your ignition on. The fuel system has been primed, so petrol has left that tank and reached the fuel filter and the fuel lines. Normally nothing more than draining, cleaning and sorting the fuel filter, so still easy.
Driven a couple of miles. Now your pump has spent those miles labouring on diluted fuel. The work is your tank, your lines, your filter and fresh fuel through the whole circuit, and how hard your car was driven matters as much as how far. Short trips, like the school run to the local primary school, are one matter. Getting as far as Aberdeen, under 50 miles away, makes a very different task — as does any miles on the M90, over 50 miles from Coplandhill, with the engine labouring hard all the way.
Driven until it complained. Clattering, a ragged idle, smoke, a throttle that has gone soft. The motor is telling you the fuel is no longer behaving like diesel. Whether it's the verge on Prunier Drive, a lay-by or a side street, stop there then leave it. A car pulled over soon very seldom has lasting damage, because the drain and the flush, which still go first, sort it out.
What Coplandhill motorists get told about petrol in a diesel — and the stories in it
Myth: topping up to full with diesel makes it fine. It does not. Nothing is removed by topping up — you're left with a fuller tank, still the same mixture. That advice presumes a diesel fuel system tolerates petrol by percentage. It does not.
Myth: "A newer diesel can cope with a bit of petrol." If anything, the reverse. At higher pressure, through finer components: that's how a modern diesel moves its fuel, and so the protection matters more, not less.
Myth: "If it starts and drives, there is no damage done." This is the one that catches drivers. Diesel in a petrol motor generally means a motor that won't run: the driver stops, and so does the damage. Nothing looks to have happened when a diesel fed petrol fires up, ticks over and drives away, as it usually will; meanwhile the pump wears. Running is not the same as fine.
Myth: "Add some two-stroke oil and drive the car home." It's an outdated fix for a distinct fault. It does not put back what petrol has weakened, and that petrol is still in your tank later on.
Myth: "Drain the tank yourself and you are sorted." Once the engine has run, some of that petrol is no longer inside your tank: it's in the filter and your lines, and it goes right back through your pump on the next start. It's also really risky to drain petrol into a can by the roadside.
How does petrol in a diesel occur?
It is seldom carelessness, and nobody does it on purpose. The forecourt makes it simple: the petrol nozzle is the smaller of the two, and it slides into a diesel filler with almost no resistance, while a diesel nozzle generally won't go into a petrol vehicle at all. So the mistake runs one way.
The moment routine stops matching the car is the moment it takes place. Hire cars, courtesy cars, and motors that are new to you. Households running one of each, petrol and diesel. A familiar forecourt with the pumps in a different order. Racing for a train at the nearest station and fuelling up en route. The first fill-up in a diesel Renault Megane after years of driving petrol is precisely the moment it takes place. Add a back seat full of children, a phone call or rain, and the hand wins.
How to prevent petrol in a diesel at your next fill-up in Coplandhill
- A green handle for unleaded and black for diesel is usual in the UK — but not on every forecourt. Go by the label on the petrol pump, not the colour.
- Inspect your filler flap. Many motors state the fuel inside the flap or on the cap. Look at it on your first fill in any vehicle you don't know.
- One of each in the household? Mark your key to the diesel — a coloured fob, a sticker — because meaning to remember is not enough.
- "Diesel", out loud, before you lift the nozzle — every time a new or hired car gets its first tank. It sounds daft. It does the trick.
- Put your phone away. This is an easy mistake to make while you're thinking about something else.
- Up to a point, a misfuel inhibitor helps: some diesels have a filler designed to reject a petrol nozzle, and add-on devices exist for the rest. Treat it as a safety net, then keep reading the pump.
- Stop the moment you realise. Less petrol inside your tank means a weaker blend. It does not change what to do next, which is still not to crank it.
Already put petrol in a diesel around Coplandhill?
Then, there's just a short order of things. Don't crank it, and don't turn the ignition on. The attendants on the forecourt — whether at Asda itself or wherever you filled up — will normally help roll it away from the petrol pump if you ask. Then call 0333 366 0103 and tell us what went in, about how much, and whether it has run.
Say so if it was AdBlue instead of petrol: it's a different issue, with its own page for Coplandhill, since AdBlue brings corrosion and deposits rather than lost protection.
Why one petrol in a diesel task in Coplandhill costs more than another
Four different tasks sit behind the four scenarios above — which is why there's no fair single quote. What shifts your cost is mostly which of them you are in. The share matters next, meaning how much of your tank is petrol, followed by the location of your car and whether getting to it is safe for a technician.
That's why our technicians ask three queries before costing rather than after: what was put in, how much, and whether it's run. A range turns into a straight figure once the answers are in.
About Coplandhill
Coplandhill is a suburban area situated on the coast of Aberdeenshire, with an elevation of 31 metres above sea level. Coplandhill lies approximately 27 miles north of Aberdeen and is surrounded by nearby places such as Middle Grange, Blackhouse, and Clerkhill. Coplandhill has a population of around 3910 residents, predominantly living in semi-detached housing. Coplandhill is located a significant distance from London, at around 420 miles away.
Fuel drain cover across Aberdeenshire, Coplandhill included
Coplandhill waits in the AB postcode area, and our vans that answer petrol in diesel calls there work the places around it as well — Middle Grange, Blackhouse and Clerkhill among them. You need not bring your vehicle to us. Forecourts, supermarket car parks, lay-bys and your own driveway are all places where we work.
Still at the petrol pump in Coplandhill?
The best place there is, then — that is where you are. Keep the vehicle turned off, then ring.