Vauxhall: Petrol in a Diesel Car? How Worried to Be
Likely less than you are now — as long as no one has started the vehicle. Everyone around Vauxhall starts with "have I wrecked it?", and the fair answer is usually no: petrol left inside that tank of any diesel remains harmless until priming, cranking or driving pulls it into your fuel system. Leave your engine off then call Petrol in Diesel — that keeps it that way. Further down, this page sets out what petrol actually does inside a diesel, how far it might have gone, and how to stop it happening to you a second time.
What petrol in a diesel does to the motor
Passing through an engine, diesel is doing two jobs at the same time. Before it combusts, it protects — then it burns. What keeps the surfaces inside the high-pressure fuel pump and the injectors from wearing down against one another is your diesel passing through them — they are designed to very fine tolerances.
Badly at the first, not at all at the second: that's petrol. It is runnier than diesel and takes away the lubrication the fuel system depends on, so a pump running on a petrol blend is a pump wearing itself. And petrol is designed to resist igniting under compression, which is the opposite of what a diesel needs from its fuel. That is where the knocking comes from.
Put these together and the shape of the issue is clear. Contact does not do the damage — movement does. Where that petrol is only in that tank, it's a problem of fuel, nothing more. After the pump has been labouring on that petrol, a mechanical issue has begun: whatever is shed by a pump that is wearing is carried downstream to the fuel injectors with the fuel.
Vauxhall, petrol in a diesel: four situations, from mild to serious
Fuelled up, never started. The best case there is. The petrol is in that tank and only that tank, and the task is a drain and a flush where your car stands. This is the one situation that can only truly occur at a forecourt, since anywhere else the vehicle has been driven to get there.
A moment's running, or just the ignition on. The fuel system has been primed, so petrol has left your tank and got to the filter and the lines. Still usually simple: drain, flush, and the filter dealt with.
A few miles driven, and the pump has spent each of them working on thinned fuel. How hard your car was driven matters as much as how far, and the work covers the tank, the fuel lines, the filter and fresh fuel through the entire system. Driving the kids to Vauxhall Primary School is one kind of trip. A run as far as Westminster, under a mile away, is a very different task. So is any distance on the M4, under 10 miles from Vauxhall, where the motor has been working hard throughout.
It complained, and only then stopped: smoke, rattling, a throttle gone soft, an idle gone ragged. What you are hearing is the motor reporting fuel that no longer runs like diesel. Leave it wherever it has stopped: a lay-by, a quiet street, the verge on Glasshouse Walk. The drain and flush still come first, and they deal with it: when a car is stopped quickly, permanent damage is very uncommon.
Stories Vauxhall motorists hear about petrol in a diesel
Myth: "Fill it the rest of the way with diesel and it'll be fine." It will not. Nothing is removed when you top up — that tank just carries more of the same mixture. The idea behind that guidance — that diesel fuel systems tolerate petrol by percentage — is wrong.
"Current diesels can handle a little petrol" — a myth, and closer to the opposite. A current diesel sends its fuel through smaller parts at higher pressure, which makes the protection count more, not less.
"It starts, it drives, and so there is no harm" — the myth that catches more people than any other. Diesel in a petrol motor generally leaves a motor that will not run: the driver stops, and so does the harm. Nothing seems to have happened when a diesel fed petrol fires up, ticks over and drives away, which it usually does; meanwhile your pump wears. Being able to run is not proof of being fine.
An old workaround for a different fault is behind this one. Myth: "Add some two-stroke oil and drive the vehicle home." What petrol has diluted remains thinned, and the petrol stays in the tank anyway.
The next start sends petrol back round your pump out of the fuel lines and the filter, where some of it ends up once the motor has run. That's why a DIY tank drain does not sort it — a myth. It is also really hazardous to drain petrol into a can by the kerbside.
How does petrol in a diesel happen?
Carelessness is rarely the cause, and no one means to do it. A diesel nozzle mostly won't fit a petrol car, but the smaller petrol nozzle goes into the filler of a diesel nearly without resistance — so forecourts make this one error straightforward, and only in one direction.
When routine and the vehicle stop matching, it occurs. A new car, a hire car or a courtesy car. Households running one of each, petrol and diesel. Your normal forecourt, its pumps now in a different order. Fuelling up in a hurry en route to the nearest station, with a train to catch. Years of petrol vehicles behind you, a diesel Renault Megane in front of you on the forecourt for its first tank — that's when. With rain, a call coming in, or children to deal with, the hand just does what it has always done.
Next time you fill up in Vauxhall: preventing petrol in a diesel
- The label is what counts, and so check the pump instead of the colour: in the UK unleaded handles are usually green and diesel black, but not on every forecourt.
- Many vehicles state the fuel type inside the filler flap or on the cap, so check it on your first fill in a vehicle you don't know.
- One of each in the household? Mark your key to your diesel — a coloured fob, a sticker — since intending to remember isn't enough.
- Say it before you lift it. On the first fill in a new or hired car, say "diesel" out loud before you lift the nozzle off the pump. It sounds silly and it works.
- Put the phone away. This is an easy mistake to make while you are thinking about something else.
- Add-on devices are available for motors without one, and some diesels are built with a filler that will not take a petrol nozzle. Helpful — but a backstop at best, never a reason to stop checking the label.
- The moment you realise, stop: less petrol inside that tank means a weaker mix. What to do next doesn't change, though — still do not fire it up.
Already put petrol in a diesel in Vauxhall?
Then, there is just a short order of things. Do not switch the ignition on, and don't crank it. Ask the staff to help you push it clear of the petrol pump if you are still at the forecourt, whether that is JET or somewhere else. What was put in, roughly how much, and whether it's run: tell us those when you ring 0333 366 0103.
Corrosion and deposits are the problem with AdBlue, whereas petrol brings lost protection. So if it was AdBlue, say so — and read its own Vauxhall page.
One petrol in a diesel job in Vauxhall costs more than another. Why?
The four scenarios above are four separate tasks, so no single quote for this would be honest. Which of them you're in is mostly what moves the cost. Where the car is counts too, and whether a van can safely get to it, after the proportion of petrol to what your tank takes.
Ahead of any quote, not after, we ask three queries: your fuel that went in, the volume, and whether it's run. That is why. Given the answers, there is a straight figure rather than a range.
About Vauxhall and where it is
Vauxhall is a suburban area in the London borough of Lambeth, situated on the south bank of the River Thames. Vauxhall sits at a low elevation of around 3 metres, close to the city centre and near the neighbouring areas of Victoria and Millbank. Vauxhall is characterized by its predominantly flat-type housing and its proximity to major landmarks like Westminster, which is approximately 0.9 miles away. Vauxhall has a population of around 17,129 people, making it a densely populated area.
Fuel drain cover across Greater London, Vauxhall included
Our vans answering petrol in diesel call-outs in Vauxhall, in the SE postcode area, also work the locations around it, Victoria, Millbank and South Lambeth included. No need to bring the car to us. Forecourts, supermarket car parks, lay-bys and your own drive are all places we drain.
In Vauxhall and still at the pump?
Then you are in the best position there is. Call, and leave it switched off.