Should You Worry? Petrol in a Diesel Car in Bluntisham
Far less than you likely are, provided it hasn't been started. Everyone in Bluntisham begins with "have I ruined it?", and the honest answer is normally no: petrol left inside that tank of any diesel stays harmless till priming, cranking or driving draws it into the system. To leave the vehicle like that, phone Petrol in Diesel and leave the motor switched off. What petrol actually does to a diesel, how to gauge how far it has travelled, and how to stop it from happening again: 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. It protects to begin with, and only then does it burn. Built to extremely fine clearances, the injectors and the pump rely on the diesel moving through them to keep their surfaces from wearing against one another.
The second task petrol does not do at all, and the first it does badly. A pump working on a petrol mixture is wearing itself out, since petrol is runnier than diesel and takes away the protection the fuel system depends on. Petrol is also designed to resist igniting under compression — the opposite of what a diesel needs from its fuel — and that's where the knocking comes.
Put these together and the shape of the problem is clear. Contact doesn't do the damage — movement does. Where the petrol is only in your tank, it is an issue of fuel, nothing more. Whatever a worn pump sheds goes on, carried by the fuel, into your injectors downstream, which is why a pump that has been working on that petrol is where a mechanical fault starts.
How serious is petrol in a diesel? Four scenarios our engineers see in Bluntisham
The best case there is: filled up, never started. At a forecourt, and truly only there, the petrol is still confined to the tank — because everywhere else the car was driven to get to it. The job is emptying and cleaning on the spot.
Your ignition switched on, or a short start. With the fuel system primed, your lines and filter now hold petrol that came from your tank. Still usually simple: drain, flush, and your filter dealt with.
Some miles driven, and your pump has spent each of them running on thinned fuel. How hard your car was driven matters as much as how far, and the work takes in your tank, the lines, the fuel filter and fresh fuel through the whole circuit. Short trips, such as the school run to St Helen's Primary School, are one matter. Driving as far as Ely, under 15 miles away, makes a very different job — as does any distance on the M11, under 10 miles from Bluntisham, with the motor labouring hard the whole time.
Driven on until it protested — rattling, smoke, a ragged idle, a dead throttle. That's your engine telling you its fuel no longer is behaving like diesel. Whether it is the verge on East Street, a lay-by or a side road, stop where you are and leave it. The fuel drain and flush still come first, and they take care of it: if a car is pulled over early, permanent damage is very uncommon.
What Bluntisham people get told about petrol in a diesel — and the myths in it
Myth: "Fill it the rest of the way with diesel and it'll be fine." It will not. Topping up removes nothing; it gives you a fuller tank of the same mixture. A diesel fuel system doesn't tolerate petrol by percentage in the way that advice presumes.
"Modern diesels can handle a little petrol" — a myth, and closer to the reverse. Protection matters more on modern diesels, not less, since their fuel runs through smaller components at higher pressure.
The myth that catches people out: if it starts and drives, it must be unharmed. A petrol engine fed diesel usually won't run, so the motorist stops and the harm stops with them. A diesel fed petrol usually starts, idles and drives away as though nothing has happened, whilst your pump grinds. Being able to run isn't the same as being fine.
Myth: "Add some two-stroke oil and drive the vehicle home." It is an old workaround for a separate fault. It doesn't put back what petrol has weakened, and the petrol is still in that tank later.
The next start sends petrol back round your pump from your lines and the filter, where some of it ends up once the engine has been run. That is why draining the tank yourself does not leave you sorted — a myth. Emptying petrol into a can at the roadside is also genuinely risky.
Petrol in a diesel: how does it happen?
Carelessness is seldom the cause, and no one means to do it. One way only, since of the nozzles: the smaller petrol one slides inside a diesel filler with almost no resistance, while the diesel one generally will not fit a petrol car. That's how the forecourt makes it straightforward.
Habit and your car getting out of step is how it occurs. A new motor, a hire car or a courtesy car. A household with one petrol and one diesel on the drive. A well-known forecourt with the pumps in a different order. A hurried fill en route to Huntingdon with a train to catch. Precisely the moment it happens: after years of driving petrol, a driver fills a diesel Volkswagen Golf for the first time. With rain, a call arriving, or a car full of children to deal with, your hand simply does what it always has.
Bluntisham motorists: how to avoid petrol in a diesel next time
- A green handle for unleaded and black for diesel is usual in the UK — but not on each forecourt. Trust the label on the petrol pump, not the colour.
- Plenty of cars state the fuel inside the filler flap or on the cap, and so check there on your first fill in any vehicle you do not know.
- Label the key. In a house 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 pump the first time you fill a hired or new car, say "diesel" out loud. Silly, perhaps, but it works.
- Thinking about something else is when this becomes an easy mistake to make, and so tuck the phone away then keep your mind on the pump.
- Up to a point, a misfuel inhibitor helps: some diesels come with a filler built to block a petrol nozzle, and add-on devices are available for the remainder. Count it as a safety net, and keep reading the pump.
- The moment you notice, stop: less petrol inside the tank makes a weaker mixture. What to do next does not change, though — still do not crank it.
Put petrol in a diesel in Bluntisham already?
Then the order of things is short. Starting it is out, and so is switching on the ignition. The attendants on the forecourt — whether at BP itself or wherever you filled up — will usually help push it clear of the petrol pump if you ask. Then phone 0333 366 0103 and tell us what went in, roughly how much, and whether it has run.
If it was AdBlue instead of petrol, say so. That's a different issue — corrosion and deposits and not lost protection — and it has its own page for Bluntisham.
What makes one Bluntisham petrol in a diesel job cost more than the next
Four separate tasks lie behind the four scenarios above — which is why there's no fair single quote. What moves your 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 place the vehicle is in and whether a van can get to it safely.
Ahead of any quote, not after, we ask three questions: the fuel that was put in, its quantity, and whether it's run. That is why. A range becomes a straight figure once those answers are in.
About Bluntisham itself
Bluntisham is a village in Cambridgeshire, situated in the Eastern region of England, with a low elevation of around 20 metres. Bluntisham lies near the cities of Ely and Cambridge, and is surrounded by smaller settlements such as East End and Wood End. Bluntisham has a population of approximately 1553 people, and is characterised by predominantly detached housing. Bluntisham is located about 58 miles from London, making it a rural community with some commuter links.
Bluntisham and Cambridgeshire: where our fuel drain cover runs
East End, Wood End and Colne are among the spots near Bluntisham that the same teams work, answering petrol in diesel jobs across Bluntisham's PE postcode area. Our engineers drain where your vehicle is — your own drive, a lay-by, a supermarket car park, a forecourt — so it never needs to come to us.
At the petrol pump in Bluntisham, still?
Then you are in the best place there can be. Keep it off. Ring.