Stanford on Avon: Petrol in a Diesel Car? How Worried to Be
Far less than you probably are, if it has not been started. "Have I ruined it?" is the first thing anyone in Stanford on Avon asks, and the honest answer is usually no, since petrol left in a diesel tank hurts nothing until it's dragged through the system — by ignition priming, by your starter, or by driving. To leave the car like that, phone Petrol in Diesel then leave the motor switched off. The remainder of this page explains 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 a second time.
Your engine and petrol in a diesel: what goes on
Two tasks fall to diesel on its route through a motor. Before it ignites, it lubricates — and then it combusts. What stops the surfaces inside the high-pressure fuel pump and the fuel injectors from wearing down against each other is your diesel passing through them — they're built to very fine gaps.
The second job petrol does not do at all, and the first it does badly. It's runnier than diesel and removes the protection the fuel system hinges on, and so a pump running on a petrol mixture is a pump wearing itself. And petrol is made to resist igniting under compression, which is the opposite of what a diesel needs from its fuel. That is where the knocking comes from.
The shape of the trouble is clear once you put those together. The damage is done by movement, not by contact. All a tank with petrol in it amounts to is a fuel issue. The start of a mechanical one is a pump that has been labouring on that petrol — and whatever a worn pump sheds moves on with the fuel to your injectors downstream.
Stanford on Avon, petrol in a diesel: four cases, from mild to serious
Fuelled up, not once started. The best case there is. Being on a forecourt is what makes this possible: elsewhere, your car has been driven there to begin with. With that petrol kept in the tank alone, it's cleared and purged right where it stands, and nothing more is needed.
Started for a moment, or just the ignition on. With your system primed, the lines and filter already contain petrol that has come from your tank. Drain, flush, see to the fuel filter: still normally straightforward.
The pump now spent a couple of miles on thinned fuel — that's what driving the vehicle meant. Tank, lines, filter, then clean fuel run through the whole system: that's this work, and the way the car was driven matters as much as the mileage. On the school run to Swinford Church of England Primary School, the miles is small. Driving as far as Coventry, under 25 miles away, makes a very different task — as does any miles on the M6, under 3 miles from Stanford on Avon, with your engine working hard all the way.
Driven on until it protested — knocking, smoke, a ragged idle, a soft throttle. That's the engine telling you its fuel has stopped acting like diesel. Whether it is the verge on Stanford Road, a lay-by or a side street, stop there then leave it. Permanent damage is very unusual when a vehicle is stopped quickly, and the drain and flush that still come first take care of it.
What Stanford on Avon drivers 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. Topping up removes nothing; it gives you a fuller tank of the same mix. A diesel fuel system doesn't tolerate petrol by percentage in the way that advice supposes.
"Current diesels can handle a little petrol" — a myth, and nearer the opposite. At higher pressure, through smaller parts: that's how a modern diesel handles its fuel, so the protection counts for more, not less.
This is the one that catches motorists. Myth: "If it starts and drives, there's no harm done." A petrol engine fed diesel normally won't run, so the driver 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 grinds. Being able to run isn't the same as being fine.
An outdated workaround for a different problem is behind this one. Myth: "Add some two-stroke oil and drive it home." It does not put back what petrol has diluted, and that petrol is still in the tank later on.
Myth: "Drain the tank yourself and you're sorted." Once the motor has run, some of the petrol is no longer inside the tank: it's in the filter and the fuel lines, and it goes straight back through your pump at the next start. Also, a can of petrol drained at the roadside is genuinely risky.
Petrol in a diesel: how does it occur?
On purpose? Never. Through carelessness? Seldom, if ever. The petrol nozzle is the narrower of the two and slips into a diesel filler with almost no resistance; a diesel nozzle generally will not go into a petrol car at all. The forecourt makes it simple, and the slip runs one way.
When habit and the car stop matching, it happens. Any motor that's new to you — a hire car, on loan as a courtesy car, or just bought. Households running one of each, petrol and diesel. A well-known forecourt with the pumps in a different order. A hurried fill on the way to Rugby with a train to catch. Precisely the moment it occurs: after years of driving petrol, someone fills a diesel Renault Clio for the first time. The hand does what it has always done once you add rain, a phone call or a back seat full of children.
How to avoid petrol in a diesel on your next fill-up around Stanford on Avon
- 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.
- The first fill in an unfamiliar car is the time to check the filler flap — inside it, or on the cap, plenty of cars state the fuel to use.
- Good intentions count for less than a sticker or a fob in a bright colour on your diesel's key if a house has one of each. So mark it.
- "Diesel", out loud, before you pick up the nozzle — every time a new or hired car needs its first tank. It seems daft. It does the trick.
- Thinking about something else is when this becomes an easy mistake to make, so put your phone away and keep your mind on the pump.
- Some diesels come with a filler designed to reject a petrol nozzle, and devices you can add are available for cars without one. Such an inhibitor helps up to a point — as a safety net, not a reason to stop checking the pump.
- Spotting it halfway? Stop at once. A thinner mix follows from less petrol in that tank, but the next stage remains the same: do not fire it up.
Already put petrol in a diesel around Stanford on Avon?
Then, there's only a short order of things. Do not turn the ignition on, and do not fire it up. Yet at the forecourt, at Eddie Stobart Truckstop - Rugby or anywhere else? Ask the attendants to help you roll it away from the petrol pump. Then ring 0333 366 0103 and tell us what got in, roughly how much, and if it's run.
Say so if it was AdBlue instead of petrol: it is a separate fault, with its own page for Stanford on Avon, since AdBlue brings corrosion and deposits rather than lost protection.
What makes one Stanford on Avon petrol in a diesel task cost more than the next
A fair single quote doesn't exist here: four situations, four separate jobs. Chiefly, the cost moves with which one you're in. The ratio matters next, meaning how much of your tank is petrol, followed by the position of the vehicle and whether getting to it is safe for a technician.
Before any quote, not after, come three queries: your fuel that got in, the quantity, and whether it's run. That is why. With those replies, you get a straight figure instead of a range.
About Stanford on Avon and where it is
Stanford on Avon is a small locality in Northamptonshire, situated on the banks of the River Avon at an elevation of around 110 metres. Stanford on Avon lies near several other villages, including Clay Coton, Swinford, and Lilbourne, and is located approximately 15 miles from Coventry. Stanford on Avon has a population of around 524 people and is characterised by predominantly detached housing. Stanford on Avon is also within commuting distance of major cities, being around 75 miles from London.
Across Northamptonshire and around Stanford on Avon: fuel drain cover
Clay Coton, Swinford and Lilbourne are among the locations near Stanford on Avon that the same teams work, answering petrol in diesel jobs across Stanford on Avon's NN postcode area. Our technicians drain where your vehicle is — your own driveway, a lay-by, a supermarket car park, a forecourt — so it does not have to come to us.
In Stanford on Avon and still at the pump?
Then you're in the best spot there can be. Switched off it stays; then phone.