Finsbury Park: Petrol in a Diesel Car? How Worried to Be
Far less than you likely are, provided it has not been started. "Have I wrecked it?" is the first question anyone around Finsbury Park asks, and the honest answer is generally no, since petrol left in a diesel tank hurts nothing till it is dragged through your fuel system — by ignition priming, by the starter, or by driving. To keep the car that way, ring Petrol in Diesel then leave the motor alone. Below, you will find what petrol actually does inside a diesel, how far it might have got, and how to stop it happening to you a second time.
Inside the motor: what petrol in a diesel really does
Passing through a motor, diesel does two things at the same time. It ignites, and before it combusts it protects. The high-pressure fuel pump and the injectors are designed to very fine gaps, and the diesel passing through them is what keeps those surfaces from wearing against each other.
Petrol handles the first task poorly and the second not at all. The clattering comes from petrol being made not to ignite when compressed, which is exactly the reverse of what a diesel needs. On top of that it is thinner than diesel, it strips away the protection your system rests on, and any pump running on that mix is wearing itself.
Put those together and the shape of the trouble is plain. Not contact but circulation is what causes the damage. All a tank with petrol in it amounts to is a fuel issue. Once your pump has been running on that petrol, a mechanical issue has begun: anything shed by a pump that's grinding is carried downstream to your injectors with your fuel.
Finsbury Park, petrol in a diesel: four situations, from mild to serious
The best case there is: filled up, not once started. At a forecourt, and truly only there, the petrol is still limited to the tank — since everywhere else the car was driven to reach it. The job is draining and rinsing on the spot.
Ignition on, or started for a moment. The system has been primed, and so petrol has left your tank and reached your filter and the fuel lines. Still generally straightforward: drain, flush, and the fuel filter dealt with.
Driven a few miles. Now your pump has spent those miles working on thinned fuel. How hard the vehicle was driven matters as much as how far, and the work takes in that tank, your lines, the filter and fresh fuel through the entire circuit. Short trips, such as the school run to Pooles Park Primary School, are one matter. Getting as far as London, under 5 miles away, makes a very different job — as does any mileage on the M1, under 10 miles from Finsbury Park, with the engine labouring hard all the way.
It protested, and only then stopped: smoke, knocking, a throttle gone soft, an idle gone uneven. The motor is telling you the fuel is no longer behaving like diesel. Whether it is the verge on Biggerstaff Street, a lay-by or a side road, stop where you are then leave it. The fuel drain and flush-through still come first, and they take care of it: if a car is stopped early, permanent damage is very unusual.
Stories Finsbury Park 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 will be." A fuller tank of the same mixture is all you get, since topping up takes out nothing. Percentage isn't how a diesel fuel system copes with petrol, whatever that advice presumes.
Myth: "A newer diesel can cope with a bit of petrol." If anything, the reverse. A current diesel sends its fuel through finer parts at higher pressure, which makes the protection matter more, not less.
One myth that catches motorists off guard: if it starts and drives, it must be unharmed. Any petrol engine fed diesel normally will not run, and so the driver stops and the damage stops with them. Nothing looks to have happened when a diesel fed petrol fires up, ticks over and drives away, as it usually will; meanwhile the pump grinds. Being able to run isn't proof of being fine.
Myth: "Add some two-stroke oil and drive the vehicle home." It's an old fix for a separate issue. The petrol is still inside your tank afterwards, and whatever it has thinned isn't put back.
"Drain it yourself and you are sorted" — a myth, since after it has been running some petrol lies in the fuel filter and lines, waiting to go straight back through your pump on the next start. Besides, petrol emptied into a can by the road is genuinely dangerous.
Why petrol in a diesel happens so easily
Nobody does it on purpose, and it's rarely carelessness. The forecourt makes it easy: the petrol nozzle is the slimmer of the two, and it slides into a diesel filler with almost no resistance, whilst a diesel nozzle mostly won't go into a petrol motor at all. So the error runs one way.
When routine and the vehicle stop matching, it occurs. Courtesy car, hire car, or a vehicle that's new. A household with one petrol and one diesel on the drive. The pumps in a different order on a familiar forecourt. A rushed fill en route to the nearest station with a train to catch. A new-to-you diesel Volkswagen Passat, its first fuelling, and a driver used to petrol: precisely when it happens. Throw in rain, a phone call or a back seat full of kids, and the hand does what it has always done.
Next time you fill up in Finsbury Park: avoiding petrol in a diesel
- Green for unleaded and black for diesel is normal in the UK — but not on every forecourt. Go by the label on the petrol pump, not the colour.
- Check your filler flap. Many motors state the fuel inside the flap or on the cap. Look at it on the first fill in any car you don't know.
- One of each in the house? Label the key to your diesel — a coloured fob, a sticker — because meaning to remember is not enough.
- "Diesel", out loud, before you lift the nozzle — each time a new or hired car needs its first tank. It seems daft. It works.
- Tuck the phone away. This is an easy mistake to make whilst you're thinking about something else.
- A misfuel inhibitor helps, up to a point. Some diesels have a filler built to reject a petrol nozzle, and add-on devices are available for motors without one. They are a backstop, not a reason to stop checking the petrol pump.
- Noticing it mid-fill? Stop there and then. A thinner mixture results from less petrol inside your tank, but the next step stays the same: do not fire it up.
Put petrol in a diesel around Finsbury Park already?
The order of things is short, then. Leave it unstarted, with your ignition off as well. If you're still on the forecourt — Texaco or anywhere else — ask the staff to help you roll the vehicle away from the pump. Next, 0333 366 0103. We will ask what got in, roughly how much, and if it has been run.
If it was AdBlue rather than petrol, say so. That's a separate issue — corrosion and deposits and not lost protection — and it has its own page for Finsbury Park.
One petrol in a diesel job in Finsbury Park costs more than another. Why?
There is no honest single price for this, because the four situations above are four different jobs. Which of them you are in is mostly what moves your cost. Where the car is matters too, and whether a van can safely reach it, after the ratio of petrol to what that tank takes.
What got in, how much, and whether it has run — three queries our engineers ask before quoting, not after, for precisely that reason. With the replies, there is a straight figure rather than a range.
About Finsbury Park itself
Finsbury Park is a suburban area in north London, situated approximately 4 miles from the city centre. Finsbury Park sits at an elevation of 34 metres, surrounded by other residential areas such as Brownswood Park, Holloway, and Stroud Green. Finsbury Park is predominantly composed of flat dwellings, housing a population of around 22,955 residents. Finsbury Park is well connected to central London, being just 3.5 miles from the city.
Across Greater London and in Finsbury Park: fuel drain cover
Finsbury Park sits in the N postcode area, and our vans that answer petrol in diesel jobs there work the places around it as well — Brownswood Park, Holloway and Stroud Green among them. The car does not need to come to us: we drain on a forecourt, in a supermarket car park, in a lay-by or on your own drive.
Still at the pump in Finsbury Park?
The best position there is, then — that is where you are. Switched off it remains; then call.