How Worried Should You Be? Petrol in a Diesel Car in Thornhill
Likely less than you already are — as long as nobody has started it. Everyone in Thornhill starts with "have I wrecked it?", and the fair answer is usually no: petrol resting in the tank of any diesel remains harmless until priming, cranking or driving pulls it into the fuel system. Petrol in Diesel is who to ring, with your engine kept off, and so it remains that way. What petrol really does to a diesel, how to gauge how far it's travelled, and how to stop it from happening again: that's the rest of this page.
Inside your engine: what petrol in a diesel does
Diesel has two jobs on its way through a motor. It protects to begin with, and after that does it burn. Designed to extremely fine gaps, the fuel injectors and the pump depend on the diesel moving through them to stop their surfaces wearing against one another.
Petrol handles the first job badly and the second not at all. A pump running on a petrol mixture is wearing itself out, because petrol is runnier than diesel and takes away the protection the fuel system relies on. Petrol is also made to resist igniting under compression — the opposite of what a diesel needs from its fuel — and that's where any rattling starts.
Put those together and the shape of the problem is clear. The harm is done by circulation, not by contact. All a tank with petrol in it amounts to is a fuel problem. After your pump has been labouring on that petrol, a mechanical issue has started: anything shed by a pump that is wearing down is carried downstream to the injectors with your fuel.
How serious is petrol in a diesel? Four scenarios our engineers see around Thornhill
Fuelled but never started — the best it gets. That petrol is inside that tank and only the tank, and the job is a drain and a flush where your car sits. This is the one scenario that can only really happen at a forecourt, since anywhere else the vehicle has been driven to get there.
Ignition on, or started for a moment. Petrol has left your tank and got to the filter and your lines, because the fuel system has been bled. Drain, flush, see to your filter: still normally simple.
Some miles driven, and the pump has spent every one of them labouring on diluted fuel. How hard your car was driven matters as much as how far, and the work takes in your tank, the lines, the fuel filter and fresh fuel through the whole circuit. Short trips, such as the school run to the local primary school, are one thing. A run as far as Carlisle, under 50 miles away, is a very different job. So is any miles on the A74(M), under 15 miles from Thornhill, where the motor has been labouring hard the whole time.
It protested, and only then stopped: smoke, rattling, a throttle gone soft, an idle gone lumpy. The fuel isn't acting like diesel any more, and the engine is telling you. Pull up where you are — on the verge on New Street, at the kerb, down a side road — and don't move it again. Long-term damage is very unusual if a vehicle is pulled over quickly, and the fuel drain and flush that still come first take care of it.
Petrol in a diesel stories Thornhill people hear
It will not be fine. The myth: "Fill it the rest of the way with diesel and it will be." Nothing is removed by topping up — you're left with a bigger tank, still the same mix. The assumption behind the advice — that diesel fuel systems tolerate petrol by percentage — is wrong.
"Current diesels can handle a little petrol" — a myth, and nearer the opposite. At higher pressure, through smaller parts: that is how a modern diesel handles its fuel, and so the protection counts for more, not less.
Myth: "If it starts and drives, there is no harm done." This is the one that catches motorists. Any petrol motor fed diesel generally will not run, so the motorist stops and the damage stops with them. A diesel fed petrol normally starts, idles and drives away as if nothing has happened, whilst the pump grinds. Running is not the same as fine.
"A drop of two-stroke oil and drive it home" — a myth, borrowed from a fix from years ago, for a separate issue. It doesn't put back what petrol has thinned, and the petrol is still inside the tank afterwards.
"Drain it yourself and you're sorted" — a myth, because after it has been running some petrol sits in the filter and lines, waiting to go right back through the pump at the next start. And, a can of petrol filled by the roadside is truly risky.
Why petrol in a diesel takes place at all
On purpose? Never. Through carelessness? Rarely, if ever. The petrol nozzle is the smaller of the two and slips into a diesel filler with almost no resistance; a diesel nozzle mostly will not go into a petrol vehicle at all. The forecourt makes it easy, and the error runs one way.
When habit and the vehicle stop matching, it happens. A new vehicle, 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. Filling up in a rush on the way to Sanquhar, with a train to catch. Years of petrol motors behind you, a diesel Volkswagen Golf in front of you at the forecourt for its first tank — that's when. With rain, a call coming in, or children to deal with, your hand simply does what it has always done.
Thornhill motorists: how to prevent petrol in a diesel next time
- Read the pump, not the colour. In the UK unleaded handles are usually green and diesel black, yet not on every forecourt. The label is what counts.
- In a car you don't know, look inside the flap over your filler or at the cap before your first fill: plenty of cars print the fuel there.
- A coloured fob or a sticker on your diesel's key does more than any amount of intending to remember, in a household with one of each.
- Say it before you lift it. On your first fill in a new or hired car, say "diesel" out loud before you lift the nozzle off the pump. It seems daft and it works.
- Put your phone away. This is an easy mistake to make while you're thinking about something else.
- Add-on devices exist for vehicles without one, and some diesels come with a filler that won't accept a petrol nozzle. Useful — but a safety net at best, never a reason to stop checking the label.
- As soon as you realise, stop: less petrol inside the tank makes a thinner mix. What to do next doesn't change, though — still do not fire it up.
Already put petrol in a diesel around Thornhill?
In that case, there's just a short order of things. Do not switch the ignition on, and do not start it. Still at the forecourt, at the nearest petrol station or anywhere else? Ask the attendants to help you push the car clear of the petrol pump. Next, 0333 366 0103. We'll ask what got in, about how much, and if it has been run.
Say so if it was AdBlue rather than petrol: it's a different issue, with its own page for Thornhill, because AdBlue brings corrosion and deposits rather than lost protection.
What makes one Thornhill petrol in a diesel task cost more than the next
There's no honest single quote for this, because the four situations above are four separate jobs. Which of them you are in is mostly what shifts your cost. Where the vehicle is counts too, and whether a van can safely get to it, after the proportion of petrol to what your tank takes.
Ahead of any quote, not after, come three queries: your fuel that got in, the amount, and whether it's run. That's why. With the replies, you get a straight figure rather than a range.
About Thornhill and its setting
Thornhill is a village situated on the banks of a river in Dumfries and Galloway, with a mix of semi-detached housing and other types of homes. Thornhill sits at an elevation of 76 metres, near the settlements of Holmhill, Townhead, and Nithbank. Thornhill is located approximately 40 miles from Carlisle and is a relatively small community with a population of around 1377 people. Thornhill has a rural setting, typical of many villages in southern Scotland.
Thornhill and Dumfries and Galloway: where our fuel drain cover runs
Our vans answering petrol in diesel jobs in Thornhill, in the DG postcode area, equally work the places near it, Holmhill, Townhead and Nithbank included. No need to move the vehicle to us. Forecourts, supermarket car parks, lay-bys and your own drive are all spots where we work.
Thornhill: still at the pump?
Then you are in the best place there is. Keep it off. Phone.