Petrol in a Diesel Car in Coalpit Hill: How Worried Should You Be?
Provided it hasn't been started, you can worry less than you likely are. Everyone in Coalpit Hill starts with "have I ruined it?", and the honest answer is usually no: petrol left in that tank of any diesel remains harmless till priming, cranking or driving draws it into your fuel system. Leave the motor off and ring Petrol in Diesel — that keeps it like that. The remainder of this page covers what petrol really does to a diesel, how to tell how far it has got, and how to make sure it doesn't happen to you a second time.
The engine and petrol in a diesel: what happens
On its way through an engine, diesel has two tasks. Oiling comes before burning; it does both. Your high-pressure pump and the injectors are designed to extremely fine clearances, and the diesel passing through them is what stops those surfaces from grinding against one another.
Of those two jobs, petrol handles the first poorly and the second never. It is thinner than diesel and removes the protection the fuel system rests on, and so a pump running on a petrol blend is a pump wearing itself. And petrol is designed to resist igniting under compression, which is the opposite of what a diesel needs from its fuel. That's where the knocking comes from.
The shape of the problem is plain once you put those together. The damage is done by circulation, not by contact. Petrol in a tank is a fuel issue. A pump that has been labouring on that petrol is the start of a mechanical one, and whatever a worn pump sheds moves on with your fuel to the fuel injectors further on.
How bad is petrol in a diesel? Four situations our engineers see around Coalpit Hill
Filled 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 the petrol held in the tank alone, it is drained and cleaned right where it stands, and nothing more is needed.
Ignition on, or started for a second. With your system primed, the lines and filter already hold petrol that has come from that tank. Usually little more than emptying, flushing and seeing to your filter, and so still simple.
The pump now worked a couple of miles on weakened fuel — that's what driving it meant. Tank, lines, filter, then clean fuel run through the entire system: that is the work, and the way the vehicle was driven matters as much as the distance. On the school run to St Saviour's CofE Academy, the miles is short. Driving as far as Stoke-on-Trent, under 10 miles away, makes a very different job — as does any miles on the M6, under 5 miles from Coalpit Hill, with your engine labouring hard the whole time.
It protested, and only then stopped: smoke, knocking, a throttle gone soft, an idle gone lumpy. The engine is telling you your fuel is no longer behaving like diesel. Leave it where it stops: a lay-by, a side street, the verge on Milton Crescent. Lasting damage is very uncommon if a vehicle is stopped early, and the fuel drain and flush that still come first deal with it.
What Coalpit Hill drivers get told about petrol in a diesel — and the stories in it
False: topping up to full with diesel makes it fine. It does not. A bigger tank of the same mixture is all it gives, because topping up takes out nothing. The assumption behind the advice — that diesel fuel systems accept petrol by percentage — is wrong.
Not so: a current diesel copes with a bit of petrol. Rather, the reverse. Protection matters more on newer diesels, not less, because their fuel runs through smaller parts at higher pressure.
Myth: "If it starts and drives, there's no harm done." This is the one that catches people. The motorist of a petrol engine fed diesel usually stops, since it will not run, and the damage stops with them. Feed petrol to a diesel and it usually fires up, idles and drives away like nothing has happened — all while its pump wears. Fine and running are not the same thing.
Myth: "Add some two-stroke oil and drive the car home." It's an outdated fix for a separate issue. It does not put back what petrol has weakened, and that petrol is still in the tank later on.
If your engine has run, part of that petrol sits in the fuel filter and the lines, not the tank — and the next start pulls it straight back through your pump. So the myth "drain that tank yourself and you are sorted" does not hold. Besides, petrol emptied into a can by the road is truly risky.
How does petrol in a diesel happen?
On purpose? Never. Through carelessness? Seldom, if ever. The forecourt makes it simple: the petrol nozzle is the slimmer 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 vehicle at all. So the slip runs one way.
The moment habit stops matching your car is the moment it takes place. Hire cars, courtesy cars, and cars that are new to you. Households running one of each, petrol and diesel. A forecourt you know, but with its pumps arranged differently. Fuelling up in a rush en route to Kidsgrove, with a train to catch. The first fill-up in a diesel Volkswagen Tiguan after years of driving petrol is exactly the moment it takes place. Add a back seat full of children, a phone call or rain, and habit takes over.
Coalpit Hill drivers: how to avoid petrol in a diesel next time
- Green for unleaded and black for diesel is usual in the UK — yet not on each forecourt. Go by the label on the pump, not the colour.
- Plenty of motors state the fuel inside the filler flap or on the cap, so check it on the first fill in any motor you don't know.
- One of each in the home? Label your key to the diesel — a coloured fob, a sticker — since meaning to remember is not enough.
- Say it before you lift it. On the first fill in a new or hired car, say "diesel" aloud before you lift the nozzle off the petrol pump. It seems silly and it does the trick.
- Mistakes like this are easy to make while your mind is on something else, and so your phone goes away.
- Up to a point, a misfuel inhibitor helps: some diesels have a filler built to refuse a petrol nozzle, and add-on devices are available for the remainder. Count it as a backstop, then keep reading the petrol pump.
- Stop the moment you realise. Less petrol inside that tank makes a thinner mix. It doesn't change what to do next, which is still not to crank it.
Already put petrol in a diesel around Coalpit Hill?
Then, there's just a short order of things. Leave it unstarted, with your ignition off too. Ask the staff to help you push it away from the pump if you are still at the forecourt, whether that's Tesco or anywhere else. Next, 0333 366 0103. We'll ask what got in, about how much, and if it's been run.
Say so if it was AdBlue rather than petrol: it's a separate issue, with its own page for Coalpit Hill, because AdBlue brings corrosion and deposits rather than lost lubrication.
Coalpit Hill petrol in a diesel tasks: why one costs more than another
An honest single price does not exist here: four situations, four separate jobs. What moves your cost is chiefly which of them you're in. Where the vehicle is matters too, and whether a van can safely get to it, after the ratio of petrol to what that tank holds.
That is why we ask three queries before pricing rather than after: what was put in, how much, and whether it has run. With those replies, there is a straight figure rather than a range.
About Coalpit Hill and its setting
Coalpit Hill is a locality in Staffordshire, situated inland at an elevation of 198 metres, approximately 5.4 miles from Stoke-on-Trent. Coalpit Hill is characterised by its predominantly detached housing stock, reflecting its residential nature. Coalpit Hill sits near several nearby places, including Talke, Hollins, and Butt Lane, in the West Midlands region.
Across Staffordshire and in Coalpit Hill: fuel drain cover
Coalpit Hill sits in the ST postcode area, and our teams that answer petrol in diesel calls there work the locations near it as well — Talke, Hollins and Butt Lane among them. A forecourt, a supermarket car park, a lay-by or your own driveway are all spots our engineers work, and the vehicle doesn't need to move to us.
In Coalpit Hill and still at the pump?
The best place there is, then — that is where you are. Turned off it stays; then phone.