Should You Worry? Petrol in a Diesel Car in Sling
Not started? Then less anxious than you probably feel. Until the ignition primes your pump, your starter turns, or your vehicle is driven, petrol in a diesel tank simply sits there and does nothing. Which makes the truthful reply to the first Sling question — "have I wrecked it?" — usually no. Leave your motor off and call Petrol in Diesel — that keeps it like that. The rest of this page explains what petrol really does to a diesel, how to judge how far it has got, and how to make sure it does not happen to you again.
Inside the motor: what petrol in a diesel does
On its way through a motor, diesel has two tasks. It burns, and before it ignites it lubricates. Designed to extremely fine tolerances, your injectors and your pump depend on your diesel moving through them to stop their surfaces wearing against one another.
The second task petrol does not do at all, and the first it does poorly. It is runnier than diesel and removes the protection your fuel system hinges 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 clattering comes from.
Combined, those make the shape of the issue plain. It's circulation that causes the damage, not contact. A tank with petrol in it is a fuel fault. Whatever a worn pump sheds travels on, carried by your fuel, into your injectors downstream, which is why a pump that has worked on that petrol is where a mechanical problem starts.
Four situations our engineers see in Sling: how serious is petrol in a diesel?
Fuelled but not once started — as good as it gets. Being on a forecourt is what makes this possible: elsewhere, the car has been driven there to begin with. With that petrol kept in your tank alone, it is cleared and flushed on the spot, and nothing more is needed.
A moment's running, or merely the ignition on. With the fuel system primed, the fuel lines and filter now hold petrol that came from the tank. Drain, flush, deal with your filter: still usually easy.
The pump now worked a couple of miles on thinned fuel — that is what driving the car does. The work is the tank, your lines, the filter and clean fuel through the entire system, and how hard your car was driven counts as much as how far. On the school run to Ellwood Primary School, the mileage is small. Any distance on the M5, under 15 miles from Sling, means the motor has worked hard throughout, and a run to Gloucester, under 25 miles away, makes a very different task too.
Driven till it protested. Knocking, a lumpy idle, smoke, a throttle that has gone soft. What you are hearing is the engine reporting fuel that no longer behaves like diesel. Leave it where it stops: a lay-by, a quiet street, the verge on Marsh Way. The drain and flush still come first, and they sort it out: if a vehicle is pulled over soon, permanent damage is very rare.
Stories Sling drivers 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. Nothing is removed when you top up — your tank simply holds more of the same mixture. A diesel fuel system doesn't tolerate petrol by percentage in the way that advice presumes.
Myth: a current diesel copes with a bit of petrol. If anything, the opposite. Lubrication counts more on modern diesels, not less, because their fuel passes through more precise components at higher pressure.
Myth: "If it starts and drives, there is no damage done." This is the one that catches motorists. Diesel in a petrol motor generally leaves a motor that will not run: the motorist stops, and so does the damage. Feed petrol to a diesel and it usually starts, ticks over and drives away as if nothing has happened — all while its pump wears. A running engine does not mean fine.
An outdated fix for a separate problem is behind this one. Myth: "Add some two-stroke oil and drive the car home." None of what petrol diluted gets put back by it — and afterwards, your tank still holds the petrol.
"Drain it yourself and you are sorted" — a myth, because after it has been running some petrol sits in the fuel filter and lines, waiting to go straight back through your pump at the next start. It is also really dangerous to drain petrol into a can at the roadside.
Petrol in a diesel: how does it occur?
It is seldom carelessness, and no one does it on purpose. The forecourt makes it simple: the petrol nozzle is the narrower of the two, and it slips into a diesel filler with almost no resistance, whilst a diesel nozzle mostly will not go into a petrol car at all. So the slip runs one way.
The moment habit stops matching the vehicle is the moment it happens. A new motor, a hire car or a courtesy car. Households running one of each, petrol and diesel. The pumps in a different order on a familiar forecourt. A train to catch, and a hurried fill en route to Lydney. The first fill-up in a diesel Volkswagen Passat after years of driving petrol is exactly the moment it takes place. Throw in rain, a phone call or a back seat full of kids, and the hand repeats what it has always done.
Avoiding petrol in a diesel next time you fill up around Sling
- Green for unleaded and black for diesel is normal in the UK — yet not on every forecourt. Trust the label on the pump, not the colour.
- The first fill in an unfamiliar vehicle is the time to check the filler flap — inside it, or on the cap, many cars state which fuel they take.
- A coloured fob or a sticker on the diesel's key achieves more than any amount of intending to remember, for 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 daft. It works.
- Mistakes like this are simple to make whilst your mind is on something else, and so your phone goes away.
- A misfuel inhibitor helps, up to a point. Some diesels come with a filler built to reject a petrol nozzle, and add-on devices exist for vehicles without one. They are a backstop, not a reason to stop checking the petrol pump.
- As soon as you notice, stop: less petrol in your tank makes a thinner mix. What to do next does not change, though — still do not fire it up.
Petrol already in a diesel in Sling? Start here
The order of things is short, then. Never crank it, and don't turn your ignition on. The attendants at the forecourt — whether at Texaco itself or wherever you filled up — will usually help roll it clear of the pump if you ask. Then call 0333 366 0103 and tell us what went in, about how much, and whether it's run.
AdBlue, not petrol? Then tell us. Corrosion and deposits, not lost protection, make it a different fault — Sling has a page all for it.
Why one petrol in a diesel task in Sling costs more than another
An honest single price doesn't exist here: four scenarios, four separate jobs. Mostly, the cost shifts with which one you're in. Where the vehicle is matters too, and whether a van can safely get to it, after the proportion of petrol to what that tank takes.
That is why our engineers ask three questions before quoting instead of after: what got in, how much, and whether it has run. Those replies turn a range into a straight figure.
About Sling itself
Sling is a small village in Gloucestershire, situated inland at an elevation of around 200 metres, with semi-detached housing being the predominant type of accommodation. Sling lies near several other small settlements, including Marsh Lane, Ellwood, and Clements End, and is approximately 16.7 miles from the city of Gloucester. Sling has a population of around 895 people and is located in the South West region of England, about 107.7 miles from London.
Across Gloucestershire and around Sling: fuel drain cover
Marsh Lane, Ellwood and Clements End are among the places around Sling that the same teams work, answering petrol in diesel calls across Sling's GL postcode area. A forecourt, a supermarket car park, a lay-by or your own driveway are all spots our engineers drain, and the vehicle doesn't need to come to us.
In Sling and still at the pump?
No position is better: that is where you are. Keep it switched off, and ring.