Petrol in a Diesel Car in Hundon: How Worried Should You Be?
If it has not been started, you can worry less than you probably are. Until the ignition primes the pump, the starter cranks, or your car is driven, petrol in a diesel tank just waits there and does no harm. Which means the truthful reply to the first Hundon question — "have I ruined it?" — usually no. Leave the engine off then call Petrol in Diesel — that is how you keep it that way. Below, this page sets out what petrol actually does inside a diesel, how far it may have gone, and how to stop it happening to you a second time.
Inside your engine: what petrol in a diesel really does
Diesel does two jobs on its way through an engine. It burns, and before it ignites it protects. What keeps the surfaces inside your high-pressure pump and your injectors from wearing against each other is your diesel passing through them — they're designed to extremely fine clearances.
The second task petrol does not do at all, and the first it does poorly. Being less viscous than diesel, petrol strips out the lubrication a fuel system needs, leaving a pump on the mixture to wear itself. It is equally made to resist igniting under compression — the opposite of what a diesel needs — which is why you get the knocking.
Taken together, they show the shape the trouble takes. The harm is done by circulation, not by contact. All a tank with petrol in it amounts to is a fuel issue. After the pump has been working on that petrol, a mechanical issue has started: anything shed by a pump that's wearing travels onward to the fuel injectors with the fuel.
Four scenarios our engineers see around Hundon: how serious is petrol in a diesel?
Fuelled up, never started. The best case there is. The petrol is inside that tank and only that tank, and the job is a drain and a flush where your car sits. This is the one situation that can only really happen at a forecourt, since anywhere else the car has been driven to get there.
Your ignition switched on, or a short start. Once primed, the fuel system has drawn petrol out of your tank as far as your filter and the fuel lines. That's normally still a straightforward task — a drain, a flush, and the filter seen to.
The pump now worked a couple of miles on thinned fuel — that is what driving it does. Tank, lines, filter, then clean fuel put through the whole circuit: that's the work, and the way your car was driven counts as much as the miles. A school run to Hundon Community Primary School is one thing. Any distance on the M11, under 15 miles from Hundon, means your engine working hard throughout, and a run to Cambridge, under 25 miles away, makes a very different task too.
Driven on till it complained — knocking, smoke, a lumpy idle, a dead throttle. What you are hearing is the engine signalling fuel that no longer runs like diesel. Whether it's the verge on Church Street, a lay-by or a side street, stop where you are and leave it. What goes first is still the fuel drain and flush, and that takes care of it, with long-term damage very rare if a vehicle is stopped early.
Petrol in a diesel myths Hundon people hear
It will not be fine. The myth: "Fill it the rest of the way with diesel and it'll be." Nothing is removed by topping up — you are left with a fuller tank, still the same mixture. That guidance presumes a diesel fuel system handles petrol by percentage. It doesn't.
If anything, the opposite is true. Myth: "A current diesel can cope with a bit of petrol." At higher pressure, through more precise parts: that is how a modern diesel handles its fuel, so the lubrication matters for more, not less.
This is the one that catches drivers. Myth: "If it starts and drives, there is no harm done." Diesel in a petrol motor usually means a motor that won't run: the driver stops, and so does the damage. A diesel fed petrol generally starts, idles and drives away as if nothing has happened, whilst your pump grinds. Being able to run is not the same as being fine.
An outdated fix for a different fault is behind this one. Myth: "Add some two-stroke oil and drive the vehicle home." None of what petrol thinned is put back by it — and later, your tank still contains the petrol.
Myth: "Drain your tank yourself and you're sorted." After the engine has been run, some of the petrol is no longer inside that tank: it is in the fuel filter and the fuel lines, and it goes right back through the pump at your next start. It's also genuinely risky to drain petrol into a can by the kerbside.
How does petrol in a diesel occur?
On purpose? Never. Through carelessness? Seldom, if ever. One way only, since of the nozzles: the smaller petrol one slips inside a diesel filler with almost no resistance, whereas the diesel one generally won't fit a petrol car. That is how the forecourt makes it simple.
When habit and the vehicle stop matching, it happens. Courtesy car, hire car, or a vehicle that's brand new. Households running one of each, petrol and diesel. A forecourt you know, but with its pumps arranged differently. Racing for a train at Dullingham and fuelling up en route. Years of petrol cars behind you, a diesel Renault Megane in front of you on the forecourt for its first tank — that is when. With rain, a call arriving, or a car full of children to deal with, your hand just does what it always has.
Next time you fill up in Hundon: preventing petrol in a diesel
- Check the pump, not the colour. In the UK unleaded handles are normally green and diesel black, yet not on each forecourt. The label is what counts.
- The first fill in an unfamiliar car is the time to check the filler flap — on it, or on the cap, plenty of cars state which fuel they take.
- One of each in the home? Mark your key to your diesel — a coloured fob, a sticker — since intending to remember is not enough.
- Say it before you lift it. On the first fill in a new or hired car, say "diesel" aloud before you take the nozzle off the petrol pump. It seems silly and it does the trick.
- 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.
- Some diesels come with a filler built to refuse a petrol nozzle, and devices you can add are available for vehicles without one. Such an inhibitor helps up to a point — as a backstop, not a reason to stop checking the petrol pump.
- The moment you realise, stop: less petrol in your tank means a thinner mix. What to do next does not change, though — still don't crank it.
Hundon: already put petrol in a diesel?
Then the order of things is short. Do not fire it up, and do not turn your ignition on. The attendants on the forecourt — whether at the nearest petrol station itself or wherever you filled up — will normally help push it clear of the pump if you ask. Next, 0333 366 0103. We will ask what went in, about how much, and if it's been run.
AdBlue, not petrol? Then say so. Corrosion and deposits, not lost lubrication, make it a separate issue — Hundon has a page all for it.
One petrol in a diesel job around Hundon costs more than another. Why?
A fair single price doesn't exist here: four scenarios, four separate jobs. What shifts the cost is chiefly which of them you are in. Two things come after that: the petrol that was put in as a share of what your tank holds, then the place the car is in and whether a technician can get to it safely.
What got in, how much, and if it has run — three questions we ask before costing, not after, for precisely that reason. Those replies change a range into a straight figure.
About Hundon, briefly
Hundon is a rural village in Suffolk, situated inland at an elevation of around 86 metres. Hundon lies approximately 50 miles from London and 19 miles from Cambridge, with nearby places including Babel Green, Mount Pleasant, and Chimney Street. Hundon has a population of around 816 people and is characterised by predominantly detached housing.
Fuel drain cover in Hundon and across Suffolk
The vans answering petrol in diesel call-outs around Hundon, in the CO postcode area, equally work the spots near it, Babel Green, Mount Pleasant and Chimney Street included. The car doesn't need to move to us: our engineers drain at a forecourt, in a supermarket car park, in a lay-by or on your own driveway.
Hundon: still at the pump?
Nothing beats it: that is where you now are. Keep the car turned off, and ring.