Holloway: Petrol in a Diesel Car? How Worried to Be
Less than you likely are, provided it hasn't been started. Everyone in Holloway starts with "have I wrecked it?", and the honest answer is generally no: petrol resting inside that tank of any diesel remains harmless until priming, cranking or driving pulls it into the system. Petrol in Diesel is who to phone, with the motor kept off, so it remains that way. The rest of this page sets out what petrol really does to a diesel, how to judge how far it has got, and how to make sure it does not happen to you again.
The engine and petrol in a diesel: what goes on
Two jobs fall to diesel on its journey through a motor. Oiling comes before burning; it does both. What keeps the surfaces inside the high-pressure fuel pump and the injectors from wearing against each other is your diesel passing through them — they are built to very fine gaps.
Petrol does the first task badly and the second not at all. Being less viscous than diesel, petrol strips out the lubrication a fuel system needs, so a pump on the blend to wear itself. It is equally made to resist igniting under compression — the reverse of what a diesel needs — which is why you hear the knocking.
Seen together, they show what shape the issue takes. Not contact but circulation is what causes the harm. Any tank with petrol in it is a fuel issue. Whatever a worn pump sheds travels on, borne by your fuel, into the fuel injectors further along, which is why a pump that has worked on the petrol is where a mechanical problem starts.
Four scenarios our technicians see in Holloway: how bad is petrol in a diesel?
Filled up, not once started. The best case there is. The petrol is inside the tank and just your tank, and the job is a drain and a flush where the vehicle stands. This is the one scenario that can only truly happen at a forecourt, because anywhere else the vehicle has been driven to get there.
Ignition on, or started for a second. Once primed, the system has drawn petrol from your tank up to the fuel filter and the lines. Drain, flush, see to the fuel filter: still usually easy.
Driven a few miles. Now your pump has spent those miles labouring on diluted fuel. The work is that tank, the lines, your filter and fresh fuel through the whole system, and how hard the vehicle was driven matters as much as how far. Driving the children to Grafton Primary School is one sort of trip. Very different again: a run to London, under 5 miles away, or some miles on the M1, under 5 miles from Holloway, where the engine kept working hard.
Rattling, an uneven idle, smoke, a throttle gone soft: driven until it complained. The engine is telling you the fuel is no longer acting like diesel. Whether it is the verge on Holloway Road, a lay-by or a side street, stop where you are then leave it. What goes first is still the drain and flush-through, and that deals with it, with permanent damage very rare if a car is stopped soon.
What Holloway drivers get told about petrol in a diesel — and the myths in it
"Top it up the rest of the way with diesel and it'll be fine" — a myth. It won't. Nothing is removed by topping up — you are left with a fuller tank, still the same mixture. That advice supposes a diesel fuel system handles petrol by percentage. It doesn't.
"Current diesels can handle a little petrol" — a myth, and nearer the reverse. More precise components and higher pressure are the way a modern diesel runs its fuel, and that makes the protection matter more, not less.
One myth that catches drivers off guard: if it starts and drives, it must be unharmed. Diesel in a petrol motor generally leaves a motor that won't run: the motorist stops, and so does the damage. Nothing seems to have happened when a diesel fed petrol fires up, ticks over and drives away, which it usually does; meanwhile your pump wears. Being able to run isn't proof of being fine.
An old fix for a different issue is behind this one. Myth: "Add some two-stroke oil and drive it home." None of what petrol thinned gets put back by it — and afterwards, the tank still holds the petrol.
The next start sends petrol back round the pump from the fuel lines and your filter, where some of it sits after the engine has been run. That is why a DIY tank drain doesn't sort it — a myth. Also, a can of petrol filled at the kerbside is truly dangerous.
Petrol in a diesel: how does it happen?
Carelessness is seldom the cause, and nobody means to do it. A diesel nozzle generally will not fit a petrol vehicle, but the slimmer petrol nozzle goes into the filler of a diesel nearly without resistance — so forecourts make this one mistake simple, and just in one direction.
When routine and the car stop matching, it occurs. A vehicle that's new to you — hired, on loan as a courtesy car, or brand new. A household with one petrol and one diesel on the driveway. A familiar forecourt with the pumps in a different order. A rushed fill en route to Drayton Park with a train to catch. Exactly the moment it occurs: after years of driving petrol, someone fills a diesel Volkswagen Golf for the first time. With rain, a call arriving, or children to deal with, your hand just does what it has always done.
Next time you fill up in Holloway: preventing petrol in a diesel
- Read the pump, not the colour. In the UK unleaded handles are usually green and diesel black, but not on every forecourt. The label is what counts.
- Many vehicles state the fuel type inside the filler flap or on the cap, and so check there on your first fill in a motor you do not know.
- A coloured fob or a sticker on the diesel's key does more than any amount of meaning to remember, in a home with one of each.
- It sounds daft and it does the trick: on your first fill in a new or hired car, say "diesel" out loud before you lift the nozzle off the pump.
- Tuck the phone away. This is an easy mistake to make while you are thinking about something else.
- A misfuel inhibitor helps, up to a point. Some diesels come with a filler built to refuse a petrol nozzle, and add-on devices exist for motors without one. They are a safety net, not a reason to stop reading the petrol pump.
- Spotting it mid-fill? Stop at once. A thinner blend follows from less petrol in your tank, yet your next step stays the same: don't fire it up.
Already put petrol in a diesel around Holloway?
Then the order of things is short. Starting it is out, and so is switching on your ignition. Ask the staff to help you roll it away from the petrol pump if you are still on the forecourt, whether that is Esso or anywhere else. What got in, roughly how much, and whether it's run: tell us those when you phone 0333 366 0103.
Say so if it was AdBlue rather than petrol: it's a different fault, with its own page for Holloway, because AdBlue brings corrosion and deposits rather than lost protection.
Holloway petrol in a diesel jobs: why one costs more than another
There is no honest single price for this, because the four situations above are four different tasks. Which of them you are in is chiefly what moves the cost. Where the car is counts too, and whether our van can safely get to it, after the ratio of petrol to what the tank takes.
Three questions come first, before quoting, instead of after — what got in, how much, has it run — and that is the reason. The answers change a range into a straight figure.
About Holloway itself
Holloway is a densely populated suburban area in north London, situated approximately 3.5 miles from the city centre. Holloway sits at an elevation of around 34 metres, with its predominant housing stock consisting of flats. Holloway is surrounded by other notable areas, including Tufnell Park, Lower Holloway, and Finsbury Park, and is home to a diverse population of around 23,351 residents.
Across Greater London and around Holloway: fuel drain cover
Holloway waits in the N postcode area, and our teams that answer petrol in diesel calls there work the places around it as well — Tufnell Park, Lower Holloway and Finsbury Park among them. You need not bring your car to us. Forecourts, supermarket car parks, lay-bys and your own driveway are all places where we work.
Still at the pump around Holloway?
Then you're in the best position there is. Phone, and leave it switched off.