How Worried Should You Be? Petrol in a Diesel Car in Portsmouth
Probably less than you already are — provided no one has started the vehicle. "Have I wrecked it?" is the first question everyone in Portsmouth asks, and the truthful answer is generally no, since petrol resting in a diesel tank harms nothing till it's drawn through the system — by ignition priming, by the starter, or by driving. Leave the engine off and ring Petrol in Diesel — that is how you keep it that way. Further down, you will find what petrol really does inside a diesel, how far it may have got, and how to stop it happening to you a second time.
Inside the motor: what petrol in a diesel does
On its way through a motor, diesel has two jobs. Lubricating comes before burning; it does both. Designed to very fine tolerances, the fuel injectors and the pump rely on the diesel moving through them to keep their surfaces from wearing against one another.
Of those two tasks, petrol handles the first badly and the second not at all. A pump working on a petrol mix is wearing itself out, because petrol is thinner than diesel and strips out the protection your fuel system depends on. Petrol is also designed to resist igniting under compression — the reverse of what a diesel wants from its fuel — and that is where any clattering starts.
Combined, those leave the shape of the issue clear. It is movement that causes the damage, not contact. All a tank with petrol in it amounts to is a fuel problem. Whatever a worn pump sheds travels on, borne by your fuel, into the fuel injectors further along, which is why a pump that has been working on the petrol is where a mechanical issue starts.
Four scenarios we see in Portsmouth: how bad is petrol in a diesel?
Filled but not once started — as good as it gets. Being on a forecourt is what makes this the case: elsewhere, the vehicle has been driven there to begin with. With the petrol kept in your tank alone, it is emptied and cleaned right where it stands, and nothing more is needed.
Started for a second, or only the ignition on. Petrol has left the tank and got to the filter and your lines, because your system has been primed. Drain, flush, deal with the fuel filter: still usually straightforward.
Driven a few miles. Now the pump has spent these miles running on thinned fuel. The work is the tank, the fuel lines, the filter and fresh fuel through the entire circuit, and how hard your car was driven matters as much as how far. The school run to Ark Ayrton Primary Academy is one matter. Any mileage on the M275, under a mile from Portsmouth, means the engine working hard throughout, and a run to Chichester, under 15 miles away, is a very different job as well.
Driven till it protested. Clattering, an uneven idle, smoke, a throttle that has gone soft. The fuel isn't behaving like diesel any more, and your engine is telling you. Whether it's the verge on Charles Dickens Street, a lay-by or a side street, stop where you are then leave it. The fuel drain and flush-through still go first, and they sort it out: if a car is pulled over quickly, permanent damage is very rare.
Portsmouth drivers and that petrol in a diesel myths they hear
Myth: "Fill it the rest of the way with diesel and it will be fine." It will not. Nothing is removed by topping up — you are left with a fuller tank, still the same mixture. Percentage isn't how a diesel fuel system tolerates petrol, whatever that advice assumes.
If anything, the reverse holds. Myth: "A newer diesel can cope with a bit of petrol." Protection counts more on current diesels, not less, because their fuel passes through finer components at higher pressure.
This is the one that fools motorists. Myth: "If it starts and drives, there is no damage done." Any petrol engine fed diesel usually won't run, so the motorist stops and the harm stops with them. Feed petrol to a diesel and it usually starts, ticks over and drives away as if nothing has happened — all while its pump wears. Being able to run is not 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 problem. What petrol has weakened stays diluted, and the petrol stays in that tank regardless.
The next start draws petrol back round your pump out of the lines and the fuel filter, where some of that ends up after your engine has been run. That is why a DIY tank drain doesn't sort it — a myth. It's also really dangerous to drain petrol into a can by the roadside.
Petrol in a diesel: how does it occur?
A careless moment is seldom the cause, and no one means to do it. The petrol nozzle is the narrower of the two and slides into a diesel filler with almost no resistance; a diesel nozzle mostly won't go into a petrol vehicle at all. The forecourt makes it easy, and the mistake runs one way.
When routine and the vehicle stop matching, it happens. Hire cars, courtesy cars, and cars that are new to you. Two vehicles on one drive, one petrol, one diesel. A forecourt you know, only with its pumps laid out differently. A train to catch, and a hurried fill on the way to Portsmouth & Southsea. A new-to-you diesel Volkswagen Golf, its first fuelling, and a driver used to petrol: exactly when it happens. Throw in rain, a phone call or a back seat full of children, and your hand does what it has always done.
How to avoid petrol in a diesel at your next fill-up around Portsmouth
- The label is what counts, so check the pump instead of the colour: in the UK unleaded handles are normally green and diesel black, but not on every forecourt.
- In a vehicle you do not know, look inside the flap over your filler or at the cap before the first fill: many motors state the fuel there.
- Good intentions count for less than a sticker or a fob in a vivid colour on the diesel's key if a house has one of each. So mark it.
- It sounds silly and it works: on your first fill in a new or hired car, say "diesel" out loud before you lift the nozzle off the petrol pump.
- While you are thinking about something else, this is an easy mistake to make — so put the phone away.
- A misfuel inhibitor helps, up to a point. Some diesels come with a filler built to reject a petrol nozzle, and add-on devices exist for motors without one. They are a safety net, not a reason to stop reading the pump.
- Noticing it halfway? Stop there and then. A thinner mix results from less petrol in that tank, but the next stage stays the same: don't fire it up.
Portsmouth: already put petrol in a diesel?
Then the order of things is short. Starting it is out, and so is switching on your ignition. If you're still on the forecourt — Esso or anywhere else — ask the staff to help you roll the car away from the pump. Next, 0333 366 0103. We will ask what went in, roughly how much, and if it's been run.
Say so if it was AdBlue instead of petrol: it is a different problem, with its own page for Portsmouth, since AdBlue brings corrosion and deposits instead of lost protection.
Portsmouth petrol in a diesel jobs: why one costs more than another
There is no fair single price for this, since the four situations above are four different tasks. Which of them you are in is chiefly what moves the cost. Where your car is counts too, and whether a technician can safely get to it, after the ratio of petrol to what your tank takes.
What got in, how much, and if it has run — three questions our engineers ask before costing, not after, for precisely that reason. A range turns into a straight figure once those replies are in.
About Portsmouth
Portsmouth is a major coastal city in southern England, situated on the shores of the Solent Strait at an elevation of around 10 metres. Portsmouth sits approximately 64 miles south-west of London and is close to the nearby city of Chichester. Portsmouth has a mix of housing types, but terraced housing is predominant, and includes areas such as Somers Town, Portsea, and Fratton. Portsmouth is home to around 151,693 people, making it a significant urban centre in the region.
Fuel drain cover across Hampshire, Portsmouth included
Somers Town, Portsea and Fratton are among the spots near Portsmouth that the same vans work, answering petrol in diesel calls across Portsmouth's PO postcode area. A forecourt, a supermarket car park, a lay-by or your own driveway are all spots we drain, and the car does not need to come to us.
Portsmouth: still at the petrol pump?
Nothing beats it: that's where you are. Keep it off. Call.