Petrol in a Diesel Car in Repton: How Worried Should You Be?
Unstarted? Then less anxious than you probably feel. Everyone around Repton starts with "have I wrecked it?", and the fair answer is usually no: petrol left inside your tank of a diesel remains harmless till priming, cranking or driving draws it into the fuel system. Petrol in Diesel is who to ring, with the motor kept off, so it remains that way. What petrol really does to a diesel, how to judge how far it has gone, and how to keep it from happening a second time: that is the remainder of this page.
What petrol in a diesel does to the engine
On its way through an engine, diesel does two jobs. Before it ignites, it protects — then it ignites. What keeps the surfaces inside the high-pressure pump and your injectors from wearing against one another is your diesel passing through them — they're made to extremely fine clearances.
Of those two jobs, petrol manages the first badly and the second never. It is thinner than diesel and removes the protection the system hinges on, and so a pump running on a petrol mix 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's where the clattering comes from.
Put those together and the shape of the issue is plain. It is circulation that does the damage, not contact. Petrol in a tank is a fuel fault. The beginning of a mechanical one is a pump that has been working on that petrol — and whatever a worn pump sheds travels on with your fuel to the injectors downstream.
How serious is petrol in a diesel? Four scenarios our engineers see around Repton
Filled up, not once started. The best case there can be. Being on a forecourt is what makes this possible: elsewhere, the car has been driven there to begin with. With the petrol held inside that tank alone, it's drained and purged right where it stands, and nothing more is needed.
A moment's running, or merely your ignition on. Once primed, the fuel system has drawn petrol out of the tank up to your filter and the lines. That's normally still a straightforward task — a drain, a flush, and the fuel filter seen to.
Those few miles driven meant the pump running on fuel weakened by petrol the whole way. Tank, lines, filter, then fresh fuel put through the entire system: that's this work, and the way your car was driven counts as much as the distance. Driving the children to Repton Primary School is one kind of trip. A run as far as Derby, under 10 miles away, is a very different task. So is any mileage on the M42, under 15 miles from Repton, where the motor has been labouring hard the whole time.
Driven on till it protested — knocking, smoke, a ragged idle, a dead throttle. The motor is telling you your fuel is no longer behaving like diesel. Leave it wherever it has stopped: a lay-by, a quiet street, the verge on Boot Hill. The drain and flush-through still come first, and they sort it out: if a car is stopped soon, lasting damage is very rare.
Repton people and the petrol in a diesel stories they hear
"Top it up the rest of the way with diesel and it will be fine" — a myth. It will not. Nothing is removed by topping up — you're left with a fuller tank, still the same mix. That advice presumes a diesel fuel system handles petrol by percentage. It doesn't.
"Modern diesels can handle a little petrol" — a myth, and closer to the opposite. Smaller components and higher pressure are how a modern diesel runs its fuel, and that makes the protection matter more, not less.
This is the one that catches drivers. Myth: "If it starts and drives, there's no damage done." The driver of a petrol motor fed diesel normally has no choice but to stop, because it will not run, and the damage stops with them. 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. Fine and running aren't the same at all.
Myth: "Add some two-stroke oil and drive the car home." It's an outdated workaround for a separate fault. What petrol has diluted remains thinned, and that petrol stays in that tank anyway.
"Drain it yourself and you're sorted" — a myth, since after it has been running some petrol lies in the fuel filter and lines, ready to go straight back through the pump at your next start. It's also genuinely dangerous to drain petrol into a can at the roadside.
Petrol in a diesel: how does it happen?
It is rarely carelessness, and no one does it on purpose. The forecourt makes it easy: the petrol nozzle is the narrower of the two, and it slips into a diesel filler with almost no resistance, while a diesel nozzle generally won't go into a petrol motor at all. So the mistake runs one way.
It takes place when habit and the vehicle stop matching. Courtesy car, hire car, or a vehicle that's new. One petrol and one diesel on the driveway of the same household. Your usual forecourt, its pumps suddenly in a different order. A train to catch, and a hurried fill on the way to Willington. A new-to-you diesel Volkswagen Golf, its first fuelling, and a driver accustomed to petrol: precisely when it happens. Throw in a back seat full of children, a phone call or rain, and habit takes over.
How to avoid petrol in a diesel at your next fill-up around Repton
- Not every forecourt in the UK keeps to green for unleaded and black for diesel, though most usually do. Read the pump's label; the colour is only a hint.
- In a motor you don't know, look inside the flap over the filler or at the cap before the first fill: plenty of motors print the fuel there.
- Label the key. In a home with one of each, a coloured fob or a sticker on the diesel's key does more than any amount of meaning to remember.
- Before the nozzle leaves the petrol pump the first time you fuel a hired or new motor, say "diesel" out loud. Silly, perhaps, yet it does the trick.
- While you are thinking about something else, this is an easy mistake to make — so put the phone away.
- Up to a point, a misfuel inhibitor helps: some diesels have a filler built to block a petrol nozzle, and aftermarket devices are available for the remainder. Count it as a backstop, and keep checking the pump.
- Spotting it halfway? Stop at once. A weaker blend follows from less petrol in the tank, yet your next step remains the same: don't fire it up.
Repton: already put petrol in a diesel?
Short and simple, then, is the order of things. Starting it is out, and so is turning on your ignition. Still on the forecourt, at BP or anywhere else? Ask the staff to help you push it clear of the pump. What was put in, about how much, and if it's run: tell us those when you phone 0333 366 0103.
Say so if it was AdBlue rather than petrol: it's a different fault, with its own page for Repton, because AdBlue brings corrosion and deposits instead of lost protection.
What makes one Repton petrol in a diesel task cost more than the next
The four situations above are four separate jobs, so no single price for this would be fair. What moves the cost is chiefly which of them you are in. Two things follow that: the petrol that was put in as a proportion of what the tank takes, then the spot the car is in and whether a technician can get to it safely.
What was put in, how much, and if it's run — three questions our engineers ask before pricing, not after, for exactly that reason. A range turns into a straight figure once those answers are in.
About Repton and where it is
Repton is a village in Derbyshire, situated on the banks of the River Trent at an elevation of 53 metres. Repton lies approximately 6.6 miles south of Derby and 109.9 miles northwest of London, with nearby villages including Cokhay Green, Milton, and Willington. Repton has a population of around 1754 people and is characterised by predominantly detached housing.
Across Derbyshire and in Repton: fuel drain cover
Petrol in diesel call-outs in Repton — part of the DE postcode area — go to teams that also cover the spots round it, Cokhay Green, Milton and Willington included. No need to bring your car to us. Forecourts, supermarket car parks, lay-bys and your own driveway are all spots where we work.
At the pump in Repton, right now?
No position is better: that's where you now are. Keep the vehicle turned off, and ring.