Tre-Ifor: Petrol in a Diesel Car? How Worried to Be
Far less than you probably are, if it hasn't been started. Everyone in Tre-Ifor begins with "have I ruined it?", and the honest answer is usually no: petrol left in the tank of a diesel stays harmless until priming, cranking or driving draws it into the fuel system. Petrol in Diesel is who to call, with your engine kept off, so it remains that way. Below, 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 again.
The motor and petrol in a diesel: what happens
On its way through a motor, diesel does two tasks. It burns, and before it ignites it lubricates. Designed to very fine clearances, the injectors and the pump depend on your diesel flowing through them to stop their surfaces wearing against one another.
Poorly at the first, not at all at the second: that is petrol. Being less viscous than diesel, petrol strips away the lubrication a fuel system needs, leaving a pump running on the blend wearing itself. It's equally made to resist igniting under compression — the opposite of what a diesel needs — which is why you get the knocking.
Seen together, they show the shape the issue has. The damage is done by circulation, not by contact. Where the petrol is only in that tank, it is a problem of fuel, nothing more. The beginning of a mechanical problem is a pump that has been working on that petrol — and whatever a worn pump sheds travels on with your fuel to the injectors downstream.
Petrol in a diesel around Tre-Ifor: how bad is it? Four situations
Fuelled, and never started: no case is better. Being at a forecourt is what makes this possible: elsewhere, the vehicle has been driven there to begin with. With that petrol held in the tank alone, it is drained and rinsed right where it stands, and nothing more is needed.
Started for a second, or just the ignition on. Petrol has left that tank and reached the filter and the lines, since the fuel system has been primed. Usually little more than emptying, flushing and sorting your filter, so still easy.
Your pump now worked a couple of miles on weakened fuel — that is what driving the car meant. How hard the car was driven matters as much as how far, and this work takes in the tank, the lines, the filter and clean fuel through the entire circuit. Driving the children to the local primary school is one sort of trip. Getting as far as Cardiff, under 25 miles away, makes a very different job — as does any miles on the M4, under 15 miles from Tre-Ifor, with your engine labouring hard the whole time.
Clattering, a ragged idle, smoke, a throttle gone soft: driven until it complained. The motor is telling you your fuel is no longer acting like diesel. Leave it where it has stopped: a lay-by, a side street, the verge on Plas Newydd Isa. Permanent damage is very uncommon when a vehicle is stopped soon, and the drain and flush that still come first deal with it.
Myths Tre-Ifor people hear about petrol in a diesel
"Top it up the rest of the way with diesel and it'll be fine" — a myth. It won't. A bigger tank of the same mix is all you get, because topping up removes nothing. A diesel fuel system doesn't accept petrol by percentage in the way that advice presumes.
If anything, the reverse holds. Myth: "A modern diesel can cope with a bit of petrol." Lubrication counts more on current diesels, not less, because their fuel passes through smaller components at higher pressure.
The myth that catches drivers out: if it starts and drives, it must be unharmed. Diesel in a petrol motor normally means a motor that will not run: the driver stops, and so does the damage. Nothing looks to have happened when a diesel fed petrol fires up, ticks over and drives away, as it usually will; meanwhile the pump grinds. Running does not mean fine.
"A drop of two-stroke oil and drive it home" — a myth, borrowed from a fix from years ago, for a different issue. It doesn't put back what petrol has diluted, and that petrol is still in your tank after that.
"Drain it yourself and you are sorted" — a myth, because after it's been running some petrol lies in your filter and lines, waiting to go straight back through your pump on your next start. It is also really dangerous to drain petrol into a can by the kerbside.
How petrol ends up: petrol in a diesel
On purpose? Never. Through carelessness? Seldom, if ever. The petrol nozzle is the slimmer of the two and slides into a diesel filler with almost no resistance; a diesel nozzle generally won't go into a petrol vehicle at all. The forecourt makes it simple, and the error runs one way.
Habit and your car getting out of step is how it occurs. A car that is new to you — a hire car, on loan as a courtesy car, or brand new. Households running one of each, petrol and diesel. The pumps in a different order on a familiar forecourt. Rushing for a train outside Aberdare and fuelling up en route. A new-to-you diesel Renault Clio, its first fuelling, and a motorist accustomed to petrol: precisely when it occurs. Your hand does what it has always done once you add rain, a phone call or a back seat full of kids.
Avoiding petrol in a diesel next time you fill up in Tre-Ifor
- Not every forecourt in the UK follows green for unleaded and black for diesel, even if most generally do. Read the pump's label; the colour is only a clue.
- Inspect your filler flap. Many motors state the fuel inside the flap or on the cap. Look at it on your first fill in a motor you do not know.
- A coloured fob or a sticker on the diesel's key achieves more than any amount of intending to remember, in a home with one of each.
- Say it before you lift it. On the first fill in a new or hired car, say "diesel" out loud before you lift the nozzle off the petrol pump. It sounds daft and it does the trick.
- Mistakes like this are easy to make whilst your mind is on something else, so the phone goes away.
- Add-on devices exist for motors without one, and some diesels come with a filler that will not take a petrol nozzle. Useful — but a backstop only, never a reason to stop checking the label.
- As soon as you realise, stop: less petrol inside the tank means a thinner blend. What to do next doesn't change, though — still don't crank it.
Already put petrol in a diesel around Tre-Ifor?
Then the order of things is short. Leave it unstarted, with your ignition off as well. Ask the attendants to help you push it away from the pump if you're still at the forecourt, whether that's Tesco or somewhere else. Then call 0333 366 0103 and tell us what went in, about how much, and if it's run.
If it was AdBlue rather than petrol, say so. That is a different issue — corrosion and deposits rather than lost lubrication — and it has its own page for Tre-Ifor.
Tre-Ifor petrol in a diesel jobs: why one costs more than another
A fair single quote doesn't exist here: four situations, four separate tasks. What moves your cost is chiefly which of them you're in. Next it's the share — how much petrol got in against how much that tank takes — and after that where the car is and whether a van can reach it safely.
That is why our engineers ask three questions before pricing rather than after: what got in, how much, and if it has run. A range becomes a straight figure when the replies are in.
About Tre-Ifor
Tre-Ifor is a small locality situated on the riverside in Rhondda Cynon Taf, with a mix of semi-detached housing and a population of around 554 residents. Tre-Ifor sits at an elevation of 228 metres, near the communities of Tre-Gibbon, Llwydcoed, and Penywaun. Tre-Ifor is located approximately 21.6 miles north of Cardiff, the capital city of Wales. Tre-Ifor is part of a wider area of south Wales that has undergone significant development over the years.
Fuel drain cover around Tre-Ifor and across Rhondda Cynon Taf
The vans answering petrol in diesel call-outs around Tre-Ifor, in the CF postcode area, also work the locations near it, Tre-Gibbon, Llwydcoed and Penywaun included. A forecourt, a supermarket car park, a lay-by or your own driveway are all places our engineers work, and the car doesn't need to come to us.
Tre-Ifor: still at the petrol pump?
In that case, you could not be in a better position. Turned off it stays; then ring.