Tain: Petrol in a Diesel Car? How Worried to Be
If it hasn't been started, worry far less than you likely are. "Have I wrecked it?" is the first thing anyone around Tain asks, and the truthful answer is usually no, since petrol left in a diesel tank harms nothing until it's drawn through the system — by ignition priming, by your starter, or by being driven. Leave the engine off and call Petrol in Diesel — that is how you keep it like that. The rest of this page sets out what petrol really does to a diesel, how to tell how far it has got, and how to make sure it does not happen to you a second time.
What petrol in a diesel does to the engine
On its way through a motor, diesel has two jobs. It burns, and before it ignites it lubricates. What stops the surfaces inside the high-pressure pump and your injectors from wearing against one another is your diesel passing through them — they are made to very fine clearances.
Poorly at the first, not at all at the second: that is petrol. The rattling comes from petrol being designed not to ignite when compressed, which is precisely the reverse of what a diesel needs. On top of that it is thinner than diesel, it strips out the lubrication the system hinges on, and any pump running on such a blend is wearing itself.
The shape of the issue is clear once you put those together. Contact doesn't do the harm — circulation does. All a tank with petrol in it amounts to is a fuel issue. After your pump has been labouring on that petrol, a mechanical fault has started: anything shed by a pump that's grinding is carried downstream to the injectors with your fuel.
Four situations our technicians see around Tain: how bad is petrol in a diesel?
Fuelled up, not once started. The best case there is. Being on a forecourt is what makes this possible: elsewhere, your car has been driven there to begin with. With that petrol kept inside your tank alone, it's cleared and rinsed right where it stands, and nothing more is needed.
A moment's running, or merely your ignition on. With your system primed, your lines and filter now contain petrol that came from your tank. Normally nothing more than draining, cleaning and sorting your filter, so still straightforward.
A few miles driven, and your pump has spent every one of them working on weakened fuel. Tank, lines, filter, then clean fuel run through the entire circuit: that is this work, and the way your car was driven matters as much as the mileage. On the school run to the local primary school, the mileage is small. Very different again: a trip to Inverness, under 25 miles away, or any miles on the M90, over 50 miles from Tain, where the motor kept running hard.
Driven till it complained. Clattering, a ragged idle, smoke, a throttle that has gone soft. That's your motor telling you its fuel no longer is acting like diesel. Whether it's the verge on King Street, a lay-by or a side road, stop there then leave it. A car pulled over early very seldom has permanent damage, because the drain and the flush, which still go first, deal with it.
Petrol in a diesel stories Tain drivers hear
False: topping up to full with diesel makes it fine. It doesn't. Nothing is removed when you top up — the tank just carries more of the same mixture. Percentage isn't how a diesel fuel system tolerates petrol, however much that guidance supposes.
Myth: "A current diesel can cope with a bit of petrol." If anything, the reverse. Finer components and higher pressure are the way a current diesel runs its fuel, and that makes the protection count more, not less.
Myth: "If it starts and drives, there's no damage done." This is the one that fools motorists. Any petrol engine fed diesel normally won't run, and so the driver stops and the harm stops with them. While your pump wears, a diesel fed petrol normally starts, ticks over and drives away as though nothing has happened. Fine and running aren't the same at all.
"A drop of two-stroke oil and drive it home" — a myth, taken from a fix from years ago, for a separate issue. That petrol is still in your tank afterwards, and whatever it has weakened isn't put back.
The next start draws petrol back round the pump out of the fuel lines and your filter, where some of it ends up after the motor has been run. That's why a DIY tank drain does not leave you sorted — a myth. On top of that, petrol emptied into a can by the road is genuinely dangerous.
How petrol ends up: petrol in a diesel
It's rarely 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, while a diesel nozzle generally will not go into a petrol motor at all. So the slip runs one way.
Habit and your car falling out of step is when it occurs. Any vehicle that is new to you — a hire car, on loan as a courtesy car, or just bought. A household with one petrol and one diesel on the driveway. The pumps in a different order on a well-known forecourt. Fuelling up in a rush on the way to the nearest station, with a train to catch. A new-to-you diesel BMW 3 Series, its first fuelling, and a motorist used to petrol: exactly when it happens. With rain, a call coming in, or a car full of children to deal with, the hand just does what it has always done.
How to avoid petrol in a diesel on your next fill-up around Tain
- Not every forecourt in the UK keeps to green for unleaded and black for diesel, even if most generally do. Read the petrol pump's label; the colour is only a hint.
- Many vehicles state the fuel inside the filler flap or on the cap, so check there on your first fill in any car you don't know.
- Good intentions do less than a sticker or a fob in a bright colour on the diesel's key when a household has one of each. So label it.
- Say it before you lift it. On the first fill in a new or hired car, say "diesel" out loud before you take the nozzle off the pump. It sounds silly and it does the trick.
- While you're thinking about something else, this is an easy mistake to make — so tuck the phone away.
- Add-on devices are available for cars without one, and some diesels are built with a filler that won't accept a petrol nozzle. Useful — but a backstop at best, never a reason to stop checking the label.
- Stop the moment you notice. Less petrol inside the tank means a thinner mixture. It does not change what to do next, which is still not to crank it.
Tain: already put petrol in a diesel?
Short and simple, then, is the order of things. Do not switch the ignition on, and don't start it. If you are still on the forecourt — Tesco or anywhere else — ask the staff to help you push the vehicle away from the petrol pump. What was put in, roughly how much, and whether it has run: tell us those when you call 0333 366 0103.
AdBlue, not petrol? Then say so. Corrosion and deposits, not lost lubrication, make it a separate problem — Tain has a page all for it.
Why one petrol in a diesel job around Tain costs more than another
Four separate tasks lie behind the four situations above — which is why there is no fair single quote. The situation itself does most of the work of moving the cost. The ratio matters next, meaning how much of your tank is petrol, followed by the location of your car and whether reaching it is safe for our van.
Ahead of any quote, not after, we ask three questions: the fuel that was put in, its quantity, and whether it has run. That's why. Given the answers, there is a straight figure rather than a range.
About Tain itself
Tain is a coastal town in the Highland county of Scotland, situated on the southern shore of the Dornoch Firth at an elevation of 26 metres. Tain lies approximately 23 miles north of Inverness and is surrounded by nearby places such as Knockbreck, Morangie, and Hilton. Tain has a population of around 3543 people and predominantly features semi-detached housing. Tain is located 462 miles northwest of London, making it a relatively remote town in the Scottish Highlands.
Fuel drain cover across Highland, Tain included
Knockbreck, Morangie and Hilton are among the spots around Tain that the same teams work, answering petrol in diesel calls across Tain's IV postcode area. No need to bring the vehicle to us. Forecourts, supermarket car parks, lay-bys and your own driveway are all spots we drain.
At the petrol pump around Tain, right now?
Nothing beats it: that's where you are. Keep it off. Phone.