Knowle: Petrol in a Diesel Car? How Worried to Be
Provided it has not been started, worry less than you likely are. "Have I ruined it?" is the first question everyone in Knowle asks, and the honest answer is generally no, because petrol resting in a diesel tank hurts nothing till it's drawn through the system — by ignition priming, by your starter, or by driving. Leave the engine off then call Petrol in Diesel — that is how you keep it like that. What petrol actually does to a diesel, how to gauge how far it has travelled, and how to keep it from happening a second time: that is the remainder of this page.
Inside your engine: what petrol in a diesel does
Two jobs fall to diesel on its journey through a motor. Lubricating comes before burning; it does both. What stops the surfaces inside the high-pressure fuel pump and the fuel injectors from wearing against each other is the diesel flowing through them — they're designed to very fine gaps.
Of those two tasks, petrol handles the first badly and the second never. The knocking comes from petrol being designed not to ignite when compressed, which is exactly the reverse of what a diesel needs. On top of that it is runnier than diesel, it strips out the protection the system rests on, and any pump running on that mixture is wearing itself.
Seen together, they show what shape the trouble takes. Not contact but circulation is what causes the harm. A tank with petrol in it is a fuel issue. A pump that has been labouring on that petrol is the start of a mechanical one, and whatever a worn pump sheds travels on with your fuel to the fuel injectors further on.
Knowle, petrol in a diesel: four cases, from mild to serious
Filled up, never started. The best case there can be. At a forecourt, and truly only there, that petrol is still limited to that tank — because everywhere else the vehicle was driven to get to it. The job is draining and purging on the spot.
Ignition on, or started for a second. Petrol has left the tank and reached your filter and the lines, because your system has been primed. Still usually straightforward: drain, flush, and the filter seen to.
Some miles driven, and the pump has spent every one of them running on diluted fuel. The work is your tank, your lines, the filter and clean fuel through the entire circuit, and how hard the car was driven matters as much as how far. Driving the children to Orchard Lea Junior School is one kind of trip. Very different once more: a run to Portsmouth, under 10 miles away, or some mileage on the M27, under a mile from Knowle, where your engine never stopped running hard.
Driven on until it protested — clattering, smoke, a ragged idle, a dead throttle. That's the engine telling you its fuel no longer is behaving like diesel. Whether it is the verge on Serotine Close, a lay-by or a side road, stop where you are and leave it. Long-term damage is very unusual when a car is pulled over early, and the drain and flush that still go first deal with it.
What Knowle motorists get told about petrol in a diesel — and the myths in it
It will not be fine. The myth: "Fill it the rest of the way with diesel and it'll be." Topping up takes out nothing; it gives you a fuller tank of the same mixture. That guidance 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. Lubrication matters more on newer diesels, not less, because their fuel runs through finer components at higher pressure.
"It starts, it drives, and so there is no harm" — the myth that catches more motorists than any other. The motorist of a petrol motor fed diesel normally stops, since it will not run, and the damage stops with them. Feed petrol to a diesel and it generally fires up, ticks over and drives away as if nothing has happened — all the while its pump is wearing. A running engine does not mean fine.
Myth: "Add some two-stroke oil and drive it home." It is an old workaround for a different issue. That petrol is still inside your tank after that, and whatever it has diluted is not put back.
The next start sends petrol back round your pump from the fuel lines and your filter, where some of it ends up once the engine has been run. That's why a DIY tank drain doesn't sort it — a myth. It is also truly risky to drain petrol into a can at the roadside.
How petrol ends up: petrol in a diesel
On purpose? Never. Through carelessness? Rarely, if ever. A diesel nozzle mostly will not go into a petrol car, yet the narrower petrol nozzle goes into the filler of a diesel nearly without resistance — so forecourts make this one mistake straightforward, and just in one direction.
The moment routine stops matching the car is the moment it happens. A vehicle that's new to you — hired, on loan as a courtesy car, or brand new. A household with one petrol and one diesel on the drive. Your ordinary forecourt, its pumps suddenly in a different order. A train to catch, and a rushed fill on the way to Fareham. Years of petrol vehicles behind you, a diesel Volkswagen Tiguan in front of you on the forecourt for its first tank — that's when. The hand does what it has always done when you add rain, a phone call or a back seat full of kids.
How to avoid petrol in a diesel on your next fill-up around Knowle
- Check the pump, not the colour. In the UK unleaded handles are generally green and diesel black, yet not on each forecourt. The label is what matters.
- Check your filler flap. Plenty of vehicles state the fuel type inside the flap or on the cap. Look at it on the first fill in any car you do not know.
- Label your key. In a home with one of each, a coloured fob or a sticker on your diesel's key does more than any amount of intending to remember.
- "Diesel", out loud, before you pick up the nozzle — every time a new or hired car needs its first tank. It seems daft. It does the trick.
- Thinking about something else is when this becomes an easy mistake to make, and so put your phone away and keep your mind on the petrol pump.
- Up to a point, a misfuel inhibitor helps: some diesels have a filler designed to refuse a petrol nozzle, and add-on devices are available for the rest. Count it as a safety net, and keep reading the pump.
- Stop as soon as you realise. Less petrol in your tank means a thinner blend. It doesn't change what to do next, which is still not to start the vehicle.
Put petrol in a diesel around Knowle already?
Then, there's only a short order of things. Starting it is out, and so is switching on the ignition. Ask the attendants to help you push it away from the pump if you're still on the forecourt, whether that's Shell or somewhere else. Then call 0333 366 0103 and tell us what went in, roughly how much, and whether it has run.
Corrosion and deposits are the problem with AdBlue, where petrol means lost protection. So if it was AdBlue, say so — and see its own Knowle page.
One petrol in a diesel task in Knowle costs more than another. Why?
There is no fair single quote for this, since the four situations above are four different tasks. The scenario itself does most of the work of moving the cost. Two things come after that: the petrol that got in as a share of what that tank holds, then the spot your car is in and whether a van can reach it safely.
Ahead of any quote, not after, come three questions: the fuel that went in, its amount, and whether it has run. That is why. With those answers, there is a straight figure rather than a range.
About Knowle, briefly
Knowle is a village situated on the riverside in Hampshire, with a relatively low elevation of 41 metres. Knowle lies near several smaller settlements, including Funtley, Tapnage, and Crockerhill, and is close to the city of Portsmouth, which is approximately 7.6 miles away. Knowle has a population of around 1487 people and is characterised by a predominance of flat housing. Knowle is also located within commuting distance of London, which is around 63.6 miles away.
Fuel drain cover across Hampshire, Knowle included
Knowle sits in the PO postcode area, and our teams that answer petrol in diesel call-outs there work the locations near it as well — Funtley, Tapnage and Crockerhill among them. The vehicle does not need to move to us: our technicians drain on a forecourt, in a supermarket car park, in a lay-by or on your own drive.
Still at the pump in Knowle?
Then you're in the best place there can be. Keep it off. Phone.