Lower Fold: Petrol in a Diesel Car? How Worried to Be
If it hasn't been started, you can worry less than you probably are. "Have I wrecked it?" is the first question anyone around Lower Fold asks, and the truthful answer is usually no, because petrol left in a diesel tank harms nothing till it's drawn through your fuel system — by ignition priming, by your starter, or by driving. Keep it like that: leave the motor off then call Petrol in Diesel. Further down, this page sets out what petrol actually 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 really does
Passing through a motor, diesel is doing two jobs at the same time. Oiling comes before burning; it does both. What stops the surfaces inside the high-pressure fuel pump and your injectors from grinding against one another is your diesel flowing through them — they are designed to extremely fine tolerances.
Badly at the first, not at all at the second: that is petrol. Being less viscous than diesel, petrol strips out the protection a fuel system needs, leaving a pump on the blend wearing itself. It's equally made to resist igniting under compression — the opposite of what a diesel needs — which is where you get the knocking.
Together, those make the shape of the issue clear. The harm is done by circulation, not by contact. All a tank with petrol in it amounts to is a fuel issue. Once your pump has been running on that petrol, a mechanical fault has started: anything shed by a pump that's wearing travels downstream to the injectors with your fuel.
Four scenarios our engineers see in Lower Fold: how serious is petrol in a diesel?
The best case there can be: filled up, not once started. That petrol is in that tank and only that tank, and the task is a drain and a flush where the car stands. This is the one situation that can only truly occur on a forecourt, since anywhere else your car has been driven to get there.
The ignition switched on, or a short start. Petrol has left the tank and got to the fuel filter and the lines, because your system has been primed. Still usually easy: drain, flush, and the fuel filter seen to.
The pump has worked a couple of miles on diluted fuel — that is what driving the car does. Miles is only half of that; how hard it was driven counts equally. Either way this work runs to the tank, the lines, your filter and clean fuel through the entire circuit. On the school run to Shawclough Community Primary School, the mileage is short. Very different once more: a trip to Manchester, under 15 miles away, or any mileage on the A627(M), under 3 miles from Lower Fold, where your engine never stopped working hard.
Driven until it complained. Rattling, an uneven idle, smoke, a throttle that has gone soft. What you are hearing is your motor reporting fuel that no longer behaves like diesel. Leave it wherever it stops: a lay-by, a quiet street, the verge on Harridge Avenue. The fuel drain and flush still come first, and they sort it out: when a car is stopped soon, lasting damage is very unusual.
Petrol in a diesel stories Lower Fold drivers hear
"Top it up the rest of the way with diesel and it'll be fine" — a myth. It will not. Nothing is removed when you top up — that tank simply holds more of the same blend. A diesel fuel system doesn't tolerate petrol by percentage in the way that guidance supposes.
Not so: a current diesel copes with a bit of petrol. Rather, the reverse. Finer parts and higher pressure are the way a newer diesel runs its fuel, and that makes the lubrication matter more, not less.
"It starts, it drives, and so no harm done" — the myth that trips up more drivers than any other. The motorist of a petrol engine fed diesel normally has no choice but to stop, since it will not run, and the harm stops with them. Nothing seems to have happened when a diesel fed petrol fires up, ticks over and drives away, as it usually will; meanwhile your pump wears. Running doesn't mean fine.
An outdated workaround for a separate issue lies behind this one. Myth: "Add some two-stroke oil and drive the vehicle home." None of what petrol weakened gets put back by it — and afterwards, your tank still holds that petrol.
"Drain it yourself and you are sorted" — a myth, since after it's been running some petrol lies in the fuel filter and lines, ready to go right back through your pump at the next start. Besides, petrol emptied into a can by the road is truly hazardous.
Why petrol in a diesel happens at all
On purpose? Never. Through carelessness? Seldom, if ever. One way only, since of the nozzles: the narrower petrol one slides inside a diesel filler with almost no resistance, whereas the diesel one mostly will not fit a petrol car. That's how the forecourt makes it straightforward.
Habit and the car getting out of step is how it takes place. Hire cars, courtesy cars, and vehicles that are new to you. Two cars on one drive, one petrol, one diesel. The pumps in a different order on a well-known forecourt. A train to catch, and a rushed fill en route to Rochdale. A new-to-you diesel Volkswagen Golf, its first fuelling, and a motorist accustomed to petrol: exactly when it occurs. Throw in rain, a phone call or a back seat full of kids, and the hand does what it has always done.
Lower Fold motorists: how to prevent petrol in a diesel next time
- The label is what counts, and so check the petrol pump instead of the colour: in the UK unleaded handles are usually green and diesel black, but not on each forecourt.
- Check your filler flap. Many motors state the fuel inside the flap or on the cap. Look at it on your first fill in a car you do not know.
- Mark the key. In a household 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 comes off the petrol pump the first time you fill a hired or new vehicle, say "diesel" aloud. Daft, perhaps, but it works.
- Whilst 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 have a filler designed to refuse a petrol nozzle, and add-on devices are available for cars without one. They are a backstop, not a reason to stop reading the petrol pump.
- Less petrol makes a weaker mix, and so stop the moment you notice — though remembering that the next step is unchanged. It is still not to start it.
Lower Fold: already put petrol in a diesel?
The order of things is brief, then. Never fire it up, and don't switch your ignition on. Yet on the forecourt, at Esso or anywhere else? Ask the attendants to help you roll the vehicle away from the petrol pump. Next, 0333 366 0103. We'll ask what got in, about how much, and if it's been run.
AdBlue, not petrol? Then say so. Corrosion and deposits, not lost protection, make it a different issue — Lower Fold has a page all for it.
One petrol in a diesel job in Lower Fold costs more than another. Why?
There's no fair single price for this, since the four scenarios above are four separate tasks. Which of them you're in is mostly what moves your cost. Beyond that it is the proportion — how much petrol got in against how much that tank holds — and then where the vehicle is and whether our van can reach it safely.
Before any quote, not after, come three queries: the fuel that was put in, the amount, and whether it's run. That is why. The answers change a range into a straight figure.
About Lower Fold
Lower Fold is a suburban area situated on the riverside in Greater Manchester, with a mix of detached housing and a population of around 4315 residents. Lower Fold sits at an elevation of 198 metres, approximately 11 miles from Manchester, and is near other local places such as Middle Healey and Lower Healey. Lower Fold is part of the wider North West region, about 170 miles from London.
Across Greater Manchester and in Lower Fold: fuel drain cover
The vans answering petrol in diesel call-outs in Lower Fold, in the OL postcode area, also work the spots around it, Middle Healey, Lower Healey and Caldershaw among them. The car does not need to move to us: our technicians drain at a forecourt, in a supermarket car park, in a lay-by or on your own driveway.
In Lower Fold and still at the pump?
No position is better: that is where you now are. Ring, and keep it switched off.