How Worried Should You Be? Petrol in a Diesel Car in Murrayfield
Unstarted? Then less anxious than you likely feel. Till the ignition primes your pump, your starter turns, or the car is driven, petrol in a diesel tank just sits there and does nothing. Which means the truthful reply to the first Murrayfield question — "have I ruined it?" — usually no. To keep the vehicle like that, call Petrol in Diesel and leave the motor switched off. The remainder of this page sets out what petrol actually does to a diesel, how to tell how far it has got, and how to make sure it does not happen to you again.
The engine and petrol in a diesel: what happens
On its way through an engine, diesel has two tasks. It burns, and before it burns it protects. What stops the surfaces inside the high-pressure fuel pump and your injectors from wearing down against one another is the diesel passing through them — they're made to very fine tolerances.
Of these two jobs, petrol manages the first poorly and the second not at all. A pump running on a petrol mix is wearing itself out, since petrol is thinner than diesel and takes away the lubrication the 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.
Together, those make the shape of the issue plain. The harm is done by movement, not by contact. Any tank with petrol in it is a fuel problem. The start of a mechanical problem is a pump that has been running on that petrol — and whatever a worn pump sheds travels on with the fuel to your injectors beyond it.
Murrayfield, petrol in a diesel: four cases, from mild to major
Fuelled but never started — the best it gets. At a forecourt, and genuinely only there, that petrol is still limited to your tank — since anywhere else your car was driven to get to it. The job is emptying and cleaning on the spot.
A brief spell of running, or just your ignition on. With the system primed, your lines and filter now hold petrol that came from your tank. Drain, flush, deal with the fuel filter: still normally easy.
Your pump has spent a couple of miles on diluted fuel — that's what driving the vehicle does. How hard the vehicle was driven matters as much as how far, and this work covers the tank, the fuel lines, the fuel filter and fresh fuel through the entire circuit. A school run to the local primary school is one thing. A run as far as Edinburgh, under 3 miles away, is a very different task. So is any distance on the M8, under 3 miles from Murrayfield, where the engine has been working hard throughout.
Clattering, a ragged idle, smoke, a throttle gone soft: driven until it complained. The fuel is not behaving like diesel any more, and the engine is telling you. Whether it is the verge on Murrayfield Drive, a lay-by or a side road, stop there and leave it. The drain and flush still go first, and they take care of it: when a car is pulled over quickly, long-term damage is very rare.
Myths Murrayfield people hear about petrol in a diesel
Myth: "Fill it the rest of the way with diesel and it'll be fine." It will not. A fuller tank of the same mixture is all it gives, because topping up removes nothing. Percentage is not how a diesel fuel system copes with petrol, whatever that advice presumes.
Not so: a modern diesel copes with a bit of petrol. If anything, the opposite. Lubrication matters more on modern diesels, not less, since their fuel passes through smaller parts at higher pressure.
"It starts, it drives, and so there is no harm" — the myth that trips up most people than any other. Feed diesel to a petrol motor and it normally won't run, so the driver stops — 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 will; meanwhile your pump grinds. Fine and running aren't the same at all.
An outdated fix for a different issue is behind this one. Myth: "Add some two-stroke oil and drive the vehicle home." It does not put back what petrol has diluted, and the petrol is still in your tank later.
Myth: "Drain the tank yourself and you're sorted." Once your engine has run, some of that petrol is no longer in that tank: it's in the filter and the lines, and it goes right back through the pump on the next start. It's also truly risky to drain petrol into a can by the kerbside.
Why petrol in a diesel takes place so easily
It's rarely carelessness, and no one does it on purpose. One way only, since of the nozzles: the slimmer petrol one slips inside a diesel filler with almost no resistance, whereas the diesel one mostly won't fit a petrol car. That's how the forecourt makes it simple.
The moment habit stops matching the vehicle is the moment it takes place. Courtesy car, hire car, or a motor that is brand new. Households running one of each, petrol and diesel. The pumps in a different order on a familiar forecourt. Racing for a train outside Haymarket and fuelling up en route. A new-to-you diesel Volkswagen Golf, its first fuelling, and a driver used to petrol: exactly when it happens. With rain, a call arriving, or a car full of children to deal with, the hand just does what it always has.
Murrayfield people: how to prevent petrol in a diesel next time
- Not every forecourt in the UK keeps to green for unleaded and black for diesel, even if most usually do. Read the pump's label; the colour is just a hint.
- Inspect your filler flap. Many motors state the fuel inside the flap or on the cap. Look at it on the first fill in any motor you don't know.
- Mark the key. In a home with one of each, a coloured fob or a sticker on your diesel's key does more than any amount of meaning to remember.
- "Diesel", aloud, before you pick up the nozzle — each time a new or hired car needs its first tank. It seems silly. It works.
- Put the phone away. This is an easy mistake to make whilst you're thinking about something else.
- Add-on devices are available for motors without one, and some diesels come with a filler that will not take a petrol nozzle. Useful — but a safety net at best, never a reason to stop checking the label.
- Stop as soon as you realise. Less petrol in the tank makes a thinner blend. It doesn't change what to do next, which is still not to crank it.
Murrayfield: already put petrol in a diesel?
The order of things is short, then. Leave it unstarted, with the ignition off too. Ask the staff to help you push it away from the pump if you are still on the forecourt, whether that is Esso or anywhere else. Phone 0333 366 0103 next, with three facts — your fuel, the approximate quantity, and if it's run.
Say so if it was AdBlue instead of petrol: it's a different fault, with its own page for Murrayfield, because AdBlue brings corrosion and deposits instead of lost lubrication.
One petrol in a diesel job in Murrayfield costs more than another. Why?
A fair single price doesn't exist here: four scenarios, four separate tasks. The situation itself does most of the work of moving the cost. The ratio matters next, meaning how much of the tank is petrol, and then the position of the vehicle and whether reaching it is safe for our van.
That's why our engineers ask three queries before costing instead of after: what got in, how much, and whether it's run. Their answers are what change a range into one firm number.
About Murrayfield
Murrayfield is a suburban area in the City of Edinburgh, situated approximately 2.3 miles west of Edinburgh's city centre. Murrayfield sits near the coast, with an elevation of around 63 metres, and is bordered by nearby places such as Ravelston, Saughtonhall, and Roseburn. Murrayfield is predominantly composed of flat-type housing, providing residential accommodation for its population of around 4347 people.
Murrayfield and City of Edinburgh: where our fuel drain cover runs
Our teams answering petrol in diesel calls in Murrayfield, in the EH postcode area, also work the spots around it, Ravelston, Saughtonhall and Roseburn among them. The vehicle does not need to come to us: we drain at a forecourt, in a supermarket car park, in a lay-by or on your own driveway.
Still at the petrol pump around Murrayfield?
The best place there is, then — that is where you are. Keep it turned off, then ring.