Three Maypoles: Petrol in a Diesel Car? How Worried to Be
Unstarted? Then less worried than you probably are. Everyone around Three Maypoles begins with "have I ruined it?", and the honest answer is usually no: petrol resting inside your tank of any diesel remains harmless till priming, cranking or driving draws it into the fuel system. To leave it that way, call Petrol in Diesel and leave your motor alone. Below, this page sets out what petrol actually does inside a diesel, how far it might have gone, and how to stop it happening to you again.
Inside the engine: what petrol in a diesel really does
Diesel has two tasks on its way through a motor. Lubricating comes before burning; it does both. Your high-pressure pump and your injectors are made to extremely fine clearances, and the diesel passing through them is what keeps those surfaces from wearing down against one another.
The second job petrol does not do at all, and the first it does badly. It is thinner than diesel and takes away the protection your fuel system hinges on, and so a pump running on a petrol mixture 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 is where the knocking comes from.
Put those together and the shape of the issue is clear. It is movement that causes the harm, not contact. Any tank with petrol in it is a fuel fault. Once the pump has been working on that petrol, a mechanical issue has started: whatever is shed by a pump that's wearing down is carried onward to the injectors with your fuel.
How bad is petrol in a diesel? Four scenarios our technicians see around Three Maypoles
Fuelled, and never started: no case is better. Just the tank has petrol in it, and so the job is clearing your tank and purging your system where your car stands. This scenario can only truly take place on a forecourt: anywhere else, the car got there by being driven.
A brief spell of running, or just your ignition on. Once primed, your system has pulled petrol from your tank as far as the filter and your lines. That is normally still an easy job — a drain, a flush, and the fuel filter dealt with.
The pump now worked a few miles on diluted fuel — that's what driving the vehicle meant. Tank, lines, filter, then fresh fuel put through the entire system: that is the work, and the way the vehicle was driven matters as much as the mileage. The school run to Dickens Heath Community Primary School is one matter. Any miles on the M42, under 3 miles from Three Maypoles, means the engine has worked hard throughout, and a run to Birmingham, under 10 miles away, makes a very different task as well.
Clattering, a lumpy idle, smoke, a throttle gone soft: driven until it complained. The motor is telling you your fuel is no longer behaving like diesel. Stop wherever you are — the verge on Tythe Barn Lane, a lay-by, a side street — and leave the car there. A vehicle pulled over early very seldom has permanent damage, as the fuel drain and the flush, which still go first, sort it out.
Petrol in a diesel myths Three Maypoles motorists hear
"Top it up the rest of the way with diesel and it'll be fine" — a myth. It won't. A fuller tank of the same mix is all it gives, because topping up takes out nothing. The assumption behind that guidance — that diesel fuel systems tolerate petrol by percentage — is wrong.
If anything, the reverse holds. 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, and so the lubrication matters for 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 looks to have happened when a diesel fed petrol fires up, ticks over and drives away, which it usually does; meanwhile your pump wears. Being able to run is not proof of being fine.
Myth: "Add some two-stroke oil and drive the car home." It's an old fix for a separate issue. It does not put back what petrol has thinned, and the petrol is still in the tank afterwards.
Once the motor has run, part of that petrol is in your filter and the fuel lines, not your tank — and the next start pulls it straight back through the pump. So the myth "drain the tank yourself and you are sorted" doesn't stand up. And, a can of petrol filled at the roadside is truly hazardous.
Why petrol in a diesel happens so easily
It is rarely carelessness, and nobody does it on purpose. One way only, since of the nozzles: the smaller petrol one slides inside a diesel filler with almost no resistance, whereas the diesel one generally will not fit a petrol vehicle. That's how the forecourt makes it simple.
The moment routine stops matching the car is the moment it happens. A new car, a hire car or a courtesy car. Households running one of each, petrol and diesel. A well-known forecourt with the pumps in a different order. Rushing for a train outside Whitlocks End and fuelling up en route. Exactly the moment it takes place: after years of driving petrol, someone fills a diesel Volkswagen Tiguan for the first time. With rain, a call coming in, or children to deal with, the hand simply does what it always has.
Avoiding petrol in a diesel next time you fill up around Three Maypoles
- Not every forecourt in the UK keeps to green for unleaded and black for diesel, even if most generally do. Check the pump's label; the colour is just a clue.
- The first fill in a strange vehicle is the time to check your filler flap — inside it, or on the cap, many motors state the fuel to use.
- One of each in the house? Label your key to the diesel — a bright fob, a sticker — because meaning to remember is not enough.
- Before the nozzle leaves the pump the first time you fill a hired or new motor, say "diesel" out loud. Silly, perhaps, but it works.
- Thinking about something else is when this becomes an easy mistake to make, so tuck your phone away and keep your mind on the petrol pump.
- Up to a point, a misfuel inhibitor helps: some diesels come with a filler designed to block a petrol nozzle, and aftermarket devices are available for the rest. Treat it as a backstop, and keep reading the petrol pump.
- Stop as soon as you notice. Less petrol in that tank makes a thinner blend. It does not change what to do next, which is still not to start the vehicle.
Petrol already in a diesel around Three Maypoles? Begin here
Then, there's only a short order of things. Starting it is out, and so is switching on your ignition. The attendants on the forecourt — whether at Sainsbury's itself or wherever you filled up — will normally help roll it clear of the petrol pump if you ask. Next, 0333 366 0103. We will ask what got in, roughly how much, and if it's been run.
If it was AdBlue rather than petrol, say so. That's a separate problem — corrosion and deposits instead of lost protection — and it has its own page for Three Maypoles.
Why one petrol in a diesel task in Three Maypoles costs more than another
The four scenarios above are four separate jobs, so no single quote for this would be honest. What moves your cost is mostly which of them you're in. The proportion matters next, meaning how much of the tank is petrol, followed by the location of the vehicle and whether reaching it is safe for a technician.
Ahead of any quote, not after, come three questions: your fuel that went in, the volume, and whether it's run. That is why. Those answers are what change a range into one firm number.
About Three Maypoles itself
Three Maypoles is a small hamlet situated on the riverside in the West Midlands, with an elevation of around 141 metres. Three Maypoles lies close to several nearby places, including Dickens Heath, Shirley Heath, and Whitlocks End, and is approximately 6.8 miles from Birmingham. Three Maypoles is characterized by its predominantly detached housing stock, reflecting its relatively rural setting within the wider urban area. Three Maypoles is also relatively distant from London, at around 94.8 miles away.
Three Maypoles and West Midlands: where our fuel drain cover runs
Three Maypoles sits in the B postcode area, and the vans that answer petrol in diesel call-outs there work the spots around it as well — Dickens Heath, Shirley Heath and Whitlocks End among them. The vehicle does not need to move to us: we drain on a forecourt, in a supermarket car park, in a lay-by or on your own driveway.
In Three Maypoles and still at the pump?
Then you are in the best position there can be. Call, and keep it turned off.