Beauchief: Petrol in a Diesel Car? How Worried to Be
Unstarted? Then less worried than you likely are. "Have I ruined it?" is the first thing everyone around Beauchief asks, and the truthful answer is generally no, because petrol left in a diesel tank hurts nothing till it is drawn through your fuel system — by ignition priming, by the starter, or by driving. Petrol in Diesel is who to call, with the engine kept off, so it remains that way. The rest 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 doesn't happen to you again.
Inside the engine: what petrol in a diesel does
On its way through an engine, diesel has two jobs. It protects to begin with, and after that does it burn. Built to extremely fine tolerances, the fuel injectors and the pump depend on your diesel flowing 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 poorly. A pump working on a petrol mixture is wearing itself out, because petrol is thinner than diesel and strips out the lubrication your fuel system relies on. Petrol is also made to resist igniting under compression — the reverse of what a diesel needs from its fuel — and that is where the knocking starts.
The shape of the problem is plain when you put those together. The harm is done by circulation, not by contact. Any tank with petrol in it is a fuel fault. Once the pump has been running on that petrol, a mechanical fault has begun: anything shed by a pump that is grinding is carried onward to your injectors with the fuel.
How bad is petrol in a diesel? Four situations our engineers see in Beauchief
Fuelled up, not once started. The best case there is. Just your tank has petrol in it, so the job is emptying that tank and rinsing the fuel system where the car stands. This situation can only truly happen on a forecourt: anywhere else, the vehicle got there by being driven.
Started for a moment, or just the ignition on. With your system primed, the fuel lines and filter already contain petrol that came from the tank. Usually nothing more than emptying, purging and sorting your filter, so still straightforward.
Your pump has spent a few miles on diluted fuel — that's what driving the vehicle meant. Mileage is only half of that; how hard it was driven matters just as much. Either way this work runs to your tank, the fuel lines, the fuel filter and clean fuel through the whole circuit. A school run to Abbey Lane Primary School is one thing. Very different a second time: a run to Sheffield, under 5 miles away, or some mileage on the M1, under 10 miles from Beauchief, where the engine kept working hard.
Knocking, a lumpy idle, smoke, a throttle gone soft: driven till it complained. The motor is telling you your fuel is no longer acting like diesel. Whether it is the verge on Abbey Lane, a lay-by or a side street, stop where you are and leave it. A vehicle pulled over quickly very seldom has lasting damage, as the drain and the flush, which still come first, deal with it.
What Beauchief people get told about petrol in a diesel — and the myths in it
"Top it up the rest of the way with diesel and it'll be fine" — a myth. It won't. Topping up removes nothing; it gives you a bigger tank of the same mixture. That advice presumes a diesel fuel system handles petrol by percentage. It doesn't.
Myth: "A newer diesel can cope with a bit of petrol." If anything, the reverse. Smaller components and higher pressure are how a newer diesel runs its fuel, and that makes the lubrication matter more, not less.
This is the one that catches drivers. Myth: "If it starts and drives, there's no damage done." Diesel in a petrol motor generally leaves a motor that will not run: the motorist stops, and so does the harm. While your pump wears, a diesel fed petrol usually starts, ticks over and drives away as though nothing has happened. Being able to run isn't the same as being fine.
"A drop of two-stroke oil and drive it home" — a myth, borrowed from a fix from years ago, for a distinct fault. That petrol is still in that tank afterwards, and what it has thinned isn't put back.
Myth: "Drain your tank yourself and you are sorted." After the engine has been run, some of the petrol is no longer in the tank: it is in the filter and the lines, and it goes right back through the pump on the next start. Emptying petrol into a can at the kerbside is also truly dangerous.
How it happens: petrol in a diesel
Carelessness is rarely the cause, and no one means to do it. The forecourt makes it easy: the petrol nozzle is the narrower of the two, and it slides into a diesel filler with almost no resistance, whilst a diesel nozzle generally won't go into a petrol car at all. So the slip runs one way.
When habit and your car stop matching, it takes place. Courtesy car, hire car, or a car that's new. A household with one petrol and one diesel on the driveway. A familiar forecourt with the pumps in a different order. A rushed fill en route to Dore & Totley with a train to catch. A new-to-you diesel Volkswagen Passat, its first fuelling, and a motorist used to petrol: precisely when it happens. Add rain, a phone call or a back seat full of children, and your hand does what it has always done.
Beauchief drivers: how to prevent petrol in a diesel next time
- The label is what matters, so read the pump instead of the colour: in the UK unleaded handles are usually green and diesel black, but not on every forecourt.
- Check the filler flap. Many cars state the fuel type inside the flap or on the cap. Look at it on the first fill in any car you don't know.
- A coloured fob or a sticker on the diesel's key achieves more than any amount of meaning to remember, in a house with one of each.
- It sounds daft and it does the trick: on the first fill in a new or hired car, say "diesel" aloud before you take the nozzle off the petrol pump.
- Whilst you are thinking about something else, this is an easy mistake to make — so put your phone away.
- Some diesels have a filler built to block a petrol nozzle, and devices you can add are available for cars without one. Such an inhibitor helps up to a point — as a backstop, not a reason to stop reading the petrol pump.
- Less petrol means a weaker mixture, so stop the moment you realise — though remembering that the next step is unchanged. It's still not to start the vehicle.
Put petrol in a diesel in Beauchief already?
Then the order of things is brief. Don't fire it up, and don't switch the ignition on. The attendants on the forecourt — whether at Sainsbury's itself or wherever you filled up — will normally help roll it clear of the pump if you ask. Ring 0333 366 0103 next, with three answers — the fuel, the rough volume, and whether it has run.
Corrosion and deposits form the problem with AdBlue, whereas petrol means lost lubrication. So if it was AdBlue, say so — and read its own Beauchief page.
Why one petrol in a diesel job in Beauchief costs more than another
The four scenarios above are four different tasks, so no single quote for this would be fair. Which of them you are in is mostly what moves the cost. After that it's the share — how much petrol got in against how much that tank holds — and after that where the car is and whether a technician can get to it safely.
That's why our technicians ask three queries before costing rather than after: what got in, how much, and whether it's run. A range becomes a straight figure when the replies are in.
About Beauchief, briefly
Beauchief is a suburban area in South Yorkshire, situated near the River Sheaf and close to the city of Sheffield. Beauchief sits at an elevation of 127 metres, with a mix of housing types but predominantly detached homes. Beauchief is located near other residential areas such as Abbeydale and Millhouses, and is about 3.6 miles from Sheffield city centre. Beauchief has a population of around 2163 people, according to recent estimates.
Fuel drain cover across South Yorkshire, Beauchief included
Abbeydale, Meadow Head and Millhouses are among the locations near Beauchief that the same vans work, answering petrol in diesel call-outs across Beauchief's S postcode area. The vehicle does not 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.
Still at the petrol pump in Beauchief?
Then you're in the best spot there can be. Leave the car switched off, and ring.