How Worried Should You Be? Petrol in a Diesel Car in Lower Clicker
Unstarted? Then less worried than you probably feel. "Have I wrecked it?" is the first thing everyone around Lower Clicker asks, and the honest answer is normally no, since petrol resting in a diesel tank hurts nothing until it's dragged through the fuel system — by ignition priming, by your starter, or by driving. To keep the car that way, phone Petrol in Diesel then leave the engine alone. What petrol actually does to a diesel, how to judge how far it has gone, and how to stop it from happening a second time: that's the rest of this page.
Inside the engine: what petrol in a diesel does
Diesel has two jobs on its way through an engine. It lubricates to begin with, and only then does it burn. Your high-pressure pump and the fuel injectors are designed to very fine clearances, and the diesel passing through them is what keeps those surfaces from wearing down against one another.
Petrol does the first task poorly and the second not at all. It is thinner than diesel and strips away the lubrication the system depends on, and so a pump running on a petrol blend is a pump wearing itself. And petrol is made to resist igniting under compression, which is the reverse of what a diesel needs from its fuel. That is where the knocking comes from.
The shape of the problem is clear when you put those together. The damage is done by movement, not by contact. All a tank with petrol in it amounts to is a fuel issue. Whatever a worn pump sheds travels on, carried by the fuel, into the fuel injectors further along, which is why a pump that has worked on that petrol is where a mechanical issue starts.
Four situations our engineers see around Lower Clicker: how bad is petrol in a diesel?
Fuelled, and never started: nothing beats it. That petrol is in your tank and only your tank, and the task is a drain and a flush where the vehicle stands. This is the one situation that can only truly occur on a forecourt, because anywhere else the car has been driven to get there.
A moment's running, or just the ignition on. Once primed, the fuel system has pulled petrol out of your tank up to the filter and your lines. Still normally easy: drain, flush, and the fuel filter sorted.
Your pump now worked a couple of miles on diluted fuel — that is what driving the vehicle meant. The work is the tank, your lines, the fuel filter and fresh fuel through the whole system, and how hard the car was driven counts as much as how far. Driving the children to Menheniot Primary School is one sort of trip. Any mileage on the M5, under 50 miles from Lower Clicker, means your engine has worked hard throughout, and a run to Plymouth, under 15 miles away, is a very different job too.
It protested, and only then stopped: smoke, rattling, a throttle gone soft, an idle gone lumpy. The fuel isn't behaving like diesel any more, and the motor is saying so. Whether it is the verge on Lower Clicker Road, a lay-by or a side street, stop where you are then leave it. A car pulled over early very seldom has lasting damage, because the drain and the flush, which still go first, deal with it.
Lower Clicker motorists and that petrol in a diesel myths they 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're left with a bigger tank, still the same mix. Percentage is not how a diesel fuel system copes with petrol, whatever that advice supposes.
Myth: "A modern diesel can cope with a bit of petrol." If anything, the reverse. At higher pressure, through finer parts: that is how a newer diesel handles its fuel, so the lubrication counts more, not less.
"It starts, it drives, so there is no harm" — the myth that catches most people than any other. The driver of a petrol engine fed diesel normally has no choice but to stop, because it will not run, and the damage stops with them. Feed petrol to a diesel and it generally starts, idles and drives away as if nothing has happened — all the while its pump wears. A running engine doesn't mean fine.
Not so: a two-stroke additive makes it safe to drive home. It is an old workaround, supposed for another problem. That petrol is still in the tank afterwards, and whatever it has thinned isn't put back.
The next start sends petrol back round your pump from the lines and the fuel filter, where some of it sits once the motor has run. That's why draining your tank yourself doesn't leave you sorted — a myth. Besides, petrol cleared into a can by the road is truly dangerous.
How it happens: petrol in a diesel
On purpose? Never. Through carelessness? Seldom, if ever. The forecourt makes it easy: the petrol nozzle is the narrower of the two, and it slides into a diesel filler with almost no resistance, while a diesel nozzle generally won't go into a petrol motor at all. So the slip runs one way.
The moment routine stops matching the vehicle is the moment it occurs. A new motor, a hire car or a courtesy car. Two motors on one driveway, one petrol, one diesel. Your usual forecourt, its pumps now in a different order. Rushing for a train at Menheniot and fuelling up en route. The first fill-up in a diesel Renault Megane after years of driving petrol is exactly the moment it occurs. Your hand does what it has always done once you add rain, a phone call or a back seat full of children.
Lower Clicker drivers: how to avoid petrol in a diesel next time
- Not every forecourt in the UK keeps to green for unleaded and black for diesel, even if most generally do. Check the petrol pump's label; the colour is just a clue.
- The first fill in an unfamiliar car is the time to check your filler flap — inside it, or on the cap, many vehicles state which fuel to use.
- A coloured fob or a sticker on your diesel's key achieves more than any amount of intending to remember, in a home with one of each.
- "Diesel", out loud, before you lift the nozzle — every time a new or hired car gets its first tank. It sounds silly. It works.
- Mistakes like this are straightforward to make whilst your mind is on something else, and so your phone goes away.
- Some diesels have a filler designed to block a petrol nozzle, and devices you can add are available for cars without one. Such an inhibitor helps up to a point — as a backstop, not a reason to stop checking the petrol pump.
- Noticing it halfway? Stop there and then. A thinner mix follows from less petrol inside the tank, yet the next stage stays the same: do not fire it up.
Petrol already in a diesel in Lower Clicker? Start here
Then the order of things is brief. Do not crank it, and don't turn the ignition on. If you're still at the forecourt — Morrisons or anywhere else — ask the attendants to help you roll the vehicle clear of the petrol pump. Ring 0333 366 0103 next, with three answers — your fuel, the rough amount, and whether it has run.
Say so if it was AdBlue rather than petrol: it is a different issue, with its own page for Lower Clicker, since AdBlue brings corrosion and deposits rather than lost lubrication.
One petrol in a diesel task in Lower Clicker costs more than another. Why?
The four scenarios above are four separate tasks, so no single quote for this would be honest. Which of them you're in is chiefly what shifts your cost. Where the car is counts too, and whether our van can safely get to it, after the ratio of petrol to what your tank takes.
Ahead of any quote, not after, come three questions: your fuel that was put in, the amount, and if it's run. That's why. Those answers are what change a range into one firm number.
About Lower Clicker and where it is
Lower Clicker is a small hamlet situated on the riverside in Cornwall, with a relatively low elevation of around 80 metres. Lower Clicker lies near several other small settlements, including Horningtops, Menheniot, and Doddycross, and is approximately 12 miles from Plymouth. Lower Clicker has a population of around 560 people, predominantly living in detached houses.
Fuel drain cover across Cornwall, Lower Clicker included
Petrol in diesel jobs in Lower Clicker — part of the PL postcode area — go to vans that also cover the locations around it, Horningtops, Menheniot and Doddycross among them. Our technicians drain wherever the vehicle is — your own drive, a lay-by, a supermarket car park, a forecourt — so it never needs to come to us.
Still at the pump around Lower Clicker?
In that case, you couldn't be in a better position. Leave the vehicle switched off, and ring.