Swingate: Petrol in a Diesel Car? How Worried to Be
Likely less than you already are — as long as nobody has started the car. Everyone in Swingate starts with "have I ruined it?", and the honest answer is generally no: petrol resting inside the tank of a diesel remains harmless until priming, cranking or driving draws it into the system. To leave the car that way, ring Petrol in Diesel and leave the engine switched off. Below, you will find what petrol really does inside a diesel, how far it might have gone, and how to stop it happening to you again.
What petrol in a diesel does to your engine
Two jobs fall to diesel on its journey through a motor. Lubricating comes before burning; it does both. Made to extremely fine gaps, the injectors and your pump depend on the diesel flowing through them to keep their surfaces from wearing against one another.
Of these two tasks, petrol manages the first poorly and the second not at all. It's runnier than diesel and removes the lubrication your fuel system rests on, 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 reverse of what a diesel needs from its fuel. That is where the knocking comes from.
Put those together and the shape of the problem is plain. Contact does not do the damage — circulation does. All a tank with petrol in it amounts to is a fuel issue. Once your pump has been working on that petrol, a mechanical problem has begun: whatever is shed by a pump that is wearing is carried downstream to the injectors with the fuel.
How bad is petrol in a diesel? Four situations we see around Swingate
Filled but never started — as good as it gets. Just that tank has petrol in it, so the job is emptying the tank and cleaning the system where the car sits. This situation can only really happen on a forecourt: anywhere else, your car got there by being driven.
A moment's running, or merely the ignition on. Petrol has left your tank and reached the filter and your lines, since the fuel system has been primed. Drain, flush, see to the filter: still normally simple.
Driven a few miles. Now your pump has spent those miles working on diluted fuel. Tank, lines, filter, then fresh fuel run through the whole circuit: that's the work, and the way the car was driven counts as much as the distance. A school run to Kimberley Primary School is one matter. Very different again: a run to Nottingham, under 5 miles away, or some mileage on the M1, under a mile from Swingate, where your engine never stopped running hard.
Driven till it complained. Clattering, a ragged idle, smoke, a throttle that has gone soft. What you are hearing is the motor reporting fuel that no longer behaves like diesel. Whether it's the verge on Knowle Lane, a lay-by or a side road, stop there and leave it. What goes first is still the fuel drain and flush-through, and that deals with it, with long-term damage very unusual when a car is pulled over soon.
What Swingate drivers get told about petrol in a diesel — and the stories in it
It will not be fine. The myth: "Fill it the rest of the way with diesel and it will be." Nothing comes out when you top up — your tank just carries more of the same blend. A diesel fuel system doesn't tolerate petrol by percentage in the way that advice presumes.
If anything, the opposite holds. Myth: "A newer diesel can cope with a bit of petrol." A current diesel sends its fuel through more precise parts at higher pressure, which makes the lubrication matter more, not less.
Myth: "If it starts and drives, there is no damage done." This is the one that catches motorists. Diesel in a petrol motor usually leaves a motor that will not run: the motorist stops, and so does the damage. Feed petrol to a diesel and it normally starts, ticks over and pulls away like nothing has happened — all the while its pump wears. Running isn't the same as fine.
"A drop of two-stroke oil and drive it home" — a myth, taken from a fix from years ago, for a separate problem. The petrol is still in your tank afterwards, and what it has thinned isn't put back.
The next start sends petrol back round the pump out of the fuel lines and the filter, where some of that sits after the engine has run. That's why a DIY tank drain doesn't sort it — a myth. Besides, petrol emptied into a can by the road is truly hazardous.
Petrol in a diesel: how does it take place?
On purpose? Never. Through carelessness? Rarely, if ever. One way only, because of the nozzles: the narrower petrol one slides inside a diesel filler with almost no resistance, whereas the diesel one mostly won't fit a petrol vehicle. That is how the forecourt makes it straightforward.
When habit and the vehicle stop matching, it happens. Any motor that's new to you — hired, on loan as a courtesy car, or just bought. A household with one petrol and one diesel on the drive. The pumps in a different order on a well-known forecourt. Racing for a train outside Ilkeston and filling up en route. A new-to-you diesel Volkswagen Golf, its first fuelling, and a motorist used to petrol: precisely when it happens. With rain, a call coming in, or a car full of children to deal with, the hand simply does what it has always done.
Swingate drivers: how to prevent petrol in a diesel next time
- A green handle for unleaded and black for diesel is normal in the UK — but not on every forecourt. Go by the label on the pump, not the colour.
- The first fill in a strange car is the time to check your filler flap — inside it, or on the cap, many motors state which fuel to use.
- Good intentions do less than a sticker or a fob in a vivid colour on your diesel's key when a home has one of each. So label it.
- Say it before you lift it. On the first fill in a new or hired car, say "diesel" aloud before you lift the nozzle off the petrol pump. It seems daft and it works.
- Mistakes like this are simple to make while your mind is on something else, and so your phone goes away.
- Add-on devices are available for vehicles without one, and some diesels are built with a filler that won't accept a petrol nozzle. Helpful — but a backstop at best, never a reason to stop checking the label.
- Less petrol makes a thinner mix, so stop the moment you notice — though remembering that the next stage is unchanged. It's still not to crank it.
Swingate: already put petrol in a diesel?
Then, there is just a short order of things. Starting it is out, and so is turning on your ignition. Ask the staff to help you push it away from the petrol pump if you are still at the forecourt, whether that's Sainsbury's or somewhere else. Then phone 0333 366 0103 and tell us what was put in, roughly how much, and whether it's run.
If it was AdBlue rather than petrol, say so. That's a different issue — corrosion and deposits and not lost lubrication — and it has its own page for Swingate.
Why one petrol in a diesel job in Swingate costs more than another
Four separate tasks lie behind the four scenarios above — which is why there's no fair single quote. Which of them you're in is mostly what shifts the cost. After that it is the ratio — how much petrol got in against how much the tank takes — and then where the car is and whether our van can reach it safely.
Before any quote, not after, come three queries: your fuel that got in, the volume, and whether it has run. That's why. Those answers change a range into a straight figure.
About Swingate
Swingate is a small village in Nottinghamshire, situated approximately 4.9 miles from Nottingham and 113 miles from London. Swingate sits at an elevation of 131 metres, surrounded by nearby places such as Kimberley, Babbington, and Nuthall. Swingate has a population of around 1237 people, predominantly living in semi-detached housing. Swingate remains a quiet residential community on the outskirts of Nottingham.
Across Nottinghamshire and in Swingate: fuel drain cover
Kimberley, Babbington and Nuthall are among the locations around Swingate that the same teams work, answering petrol in diesel call-outs across Swingate's NG postcode area. No need to move your vehicle to us. Forecourts, supermarket car parks, lay-bys and your own driveway are all places we drain.
In Swingate and still at the pump?
Nothing beats it: that's where you are. Phone, and keep it switched off.