Highgate: Petrol in a Diesel Car? How Worried to Be
Not started? Then less worried than you likely feel. Everyone in Highgate starts with "have I ruined it?", and the fair answer is generally no: petrol resting in your tank of any diesel stays harmless till priming, cranking or driving draws it into the system. Keep it like that: leave your engine off then phone Petrol in Diesel. Below, this page sets out what petrol really does inside a diesel, how far it might have got, and how to stop it happening to you a second time.
The engine and petrol in a diesel: what happens
Passing through an engine, diesel does two jobs at the same time. Before it combusts, it protects — and then it combusts. Extremely fine clearances are built into the fuel injectors and the high-pressure fuel pump, and just your diesel flowing through stops those surfaces grinding together.
Of these two tasks, petrol manages the first poorly and the second never. The rattling comes from petrol being made 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 away the protection the system rests on, and any pump working on such a blend is wearing itself.
Combined, those make the shape of the problem clear. Not contact but circulation is what causes the harm. A tank with petrol in it is a fuel issue. A pump that has been running on that petrol is the start of a mechanical one, and whatever a worn pump sheds travels on with your fuel to the fuel injectors further on.
Highgate, petrol in a diesel: four cases, from mild to significant
Filled up, not once started. The best case there can be. Being on a forecourt is what makes this the case: elsewhere, the vehicle has been driven there to begin with. With that petrol held in that tank alone, it's emptied and cleaned right where it stands, and nothing more is needed.
Ignition on, or started for a second. Once primed, your system has drawn petrol out of your tank up to the fuel filter and the fuel lines. Drain, flush, deal with the filter: still usually easy.
A few miles driven, and the pump has spent every one of them working on thinned fuel. The work is the tank, your lines, the filter and clean fuel through the whole circuit, and how hard the vehicle was driven matters as much as how far. Driving the kids to Highgate Primary Academy is one kind of trip. Getting as far as Doncaster, under 10 miles away, makes a very different task — as does any mileage on the A1(M), under 5 miles from Highgate, with the motor labouring hard the whole time.
Knocking, a lumpy idle, smoke, a throttle gone soft: driven until it complained. The engine is telling you the fuel is no longer acting like diesel. Stop on the spot — on the verge on Barnsley Road, at the kerb, down a side road — and don't move it again. What comes first is still the fuel drain and flush, and that sorts it out, with lasting damage very uncommon if a car is pulled over soon.
Myths Highgate drivers hear about petrol in a diesel
It will not be fine. The myth: "Fill it the rest of the way with diesel and it'll be." Nothing is removed by topping up — you're left with a fuller tank, still the same mix. A diesel fuel system does not tolerate petrol by percentage in the way that advice supposes.
Myth: "A newer diesel can cope with a bit of petrol." If anything, the reverse. Smaller parts and higher pressure are the way a modern diesel runs its fuel, and that makes the protection matter more, not less.
Myth: "If it starts and drives, there is no harm done." This is the one that catches people. Diesel in a petrol motor usually leaves a motor that won't run: the motorist stops, and so does the damage. Whilst the pump grinds, a diesel fed petrol usually starts, idles and drives away as though nothing has happened. Running is not the same as fine.
An old workaround for a different fault lies behind this one. Myth: "Add some two-stroke oil and drive it home." What petrol has thinned stays diluted, and that petrol stays inside that tank anyway.
"Drain it yourself and you are sorted" — a myth, since after it's been running some petrol lies in your filter and lines, ready to go right back through your pump on the next start. It is also truly dangerous to drain petrol into a can at the roadside.
How petrol ends up: petrol in a diesel
A careless moment is seldom the cause, and no one means to do it. 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 mostly will not go into a petrol motor at all. So the slip runs one way.
It takes place when routine and your car stop matching. Courtesy car, hire car, or a motor that's new. Households running one of each, petrol and diesel. A forecourt you know, but with its pumps laid out differently. A train to catch, and a hurried fill en route to Goldthorpe. The first fill-up in a diesel Renault Megane after years of driving petrol is precisely the moment it takes place. Your hand does what it has always done once you add rain, a phone call or a back seat full of kids.
Highgate people: how to avoid petrol in a diesel next time
- The label is what counts, so read the petrol pump rather than the colour: in the UK unleaded handles are normally green and diesel black, but not on each forecourt.
- The first fill in a new car is the time to check your filler flap — inside it, or on the cap, plenty of cars state the fuel to use.
- A coloured fob or a sticker on the diesel's key achieves more than any amount of intending to remember, in a household with one of each.
- "Diesel", out loud, before you lift the nozzle — each time a new or hired car needs its first tank. It seems silly. It does the trick.
- Mistakes like this are straightforward to make while your mind is on something else, and so the phone goes away.
- Add-on devices are available for motors without one, and some diesels come with a filler that will not accept a petrol nozzle. Useful — but a safety net only, never a reason to stop checking the label.
- Noticing it halfway? Stop there and then. A weaker blend results from less petrol in your tank, but your next step remains the same: don't fire it up.
Petrol already in a diesel around Highgate? Begin here
Then the order of things is brief. Do not turn your ignition on, and don't start it. Yet on the forecourt, at BP or anywhere else? Ask the staff to help you push the car clear of the pump. Next, 0333 366 0103. We will ask what got in, roughly how much, and if it's been run.
Corrosion and deposits form the trouble with AdBlue, where petrol brings lost lubrication. So if it was AdBlue, say so — and read its own Highgate page.
One petrol in a diesel job in Highgate costs more than another. Why?
A fair single price doesn't exist here: four scenarios, four separate jobs. What moves the cost is mostly which of them 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 holds.
What went in, how much, and if it has run — three questions our technicians ask before pricing, not after, for precisely that reason. Their replies are what change a range into one firm number.
About Highgate
Highgate is a suburban area in South Yorkshire, situated near the banks of a river at an elevation of around 45 metres. Highgate lies approximately 7.7 miles from Doncaster and is close to nearby places such as Goldthorpe, Thurnscoe, and Billingley. Highgate has a population of around 2500 people and is characterised by predominantly detached housing.
Fuel drain cover around Highgate and across South Yorkshire
Highgate waits in the S postcode area, and the teams that answer petrol in diesel jobs there work the spots around it as well — Goldthorpe, Thurnscoe and Billingley among them. No need to bring the car to us. Forecourts, supermarket car parks, lay-bys and your own drive are all spots we drain.
Highgate: still at the petrol pump?
Then you're in the best position there is. Keep it off. Phone.