Hackney: Petrol in a Diesel Car? How Worried to Be
Probably less than you are now — as long as no one has started the vehicle. "Have I ruined it?" is the first question anyone around Hackney asks, and the truthful answer is normally no, since petrol left in a diesel tank hurts nothing till it is drawn through the system — by ignition priming, by your starter, or by driving. Petrol in Diesel is who to ring, with your motor left off, so it remains that way. The rest of this page explains 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.
Your engine and petrol in a diesel: what happens
Two tasks fall to diesel on its route through a motor. Before it burns, it lubricates — then it burns. Very fine tolerances go into your injectors and the high-pressure pump, and just the diesel flowing through stops those surfaces grinding together.
The second task petrol doesn't do at all, and the first it does poorly. Being less viscous than diesel, petrol strips out the protection a fuel system needs, so a pump running on the blend wearing itself. It is equally made to resist igniting under compression — the opposite of what a diesel needs — which is why you get the clattering.
The shape of the problem is clear once you put those together. The harm is done by movement, not by contact. Petrol in the tank is a fuel issue. The start of a mechanical problem is a pump that has been running on that petrol — and whatever a worn pump sheds travels on with your fuel to the fuel injectors beyond it.
Four situations we see in Hackney: how serious is petrol in a diesel?
The best case there is: filled up, never started. Being on a forecourt is what makes this possible: elsewhere, your car has been driven there to begin with. With the petrol held in your tank alone, it is emptied and flushed right where it stands, and nothing more is needed.
Started for a moment, or just the ignition on. Petrol has left that tank and reached your filter and your lines, because the fuel system has been bled. Drain, flush, see to the filter: still normally easy.
A few miles driven, and your pump has spent each of them running on weakened fuel. Mileage is only half of that; how hard it was driven counts equally. Either way the work includes the tank, your lines, your filter and fresh fuel through the whole circuit. The school run to Morningside Primary School is one thing. A run as far as London, under 3 miles away, is a very different task. So is any distance on the M11, under 5 miles from Hackney, where the motor has been working hard the whole time.
Rattling, a ragged idle, smoke, a throttle gone soft: driven till it complained. The motor is telling you your fuel is no longer behaving like diesel. Stop wherever you are — the verge on Mare Street, a lay-by, a side street — and leave it there. A car pulled over early very seldom has long-term damage, as the fuel drain and the flush-through, which still go first, sort it out.
What Hackney motorists get told about petrol in a diesel — and the stories in it
It will not be fine. The myth: "Fill it the rest of the way with diesel and it will be." Nothing is removed when you top up — that tank simply carries more of the same mixture. A diesel fuel system doesn't tolerate petrol by percentage in the way that guidance presumes.
If anything, the reverse holds. Myth: "A modern diesel can cope with a bit of petrol." Lubrication counts more on current diesels, not less, since their fuel passes through smaller components at higher pressure.
"It starts, it drives, and so there is no harm" — the myth that catches most motorists than any other. Any petrol motor fed diesel normally won't run, and so the driver stops and the harm stops with them. Whilst the pump wears, a diesel fed petrol normally starts, idles and drives away as if nothing has happened. Being able to run isn't proof of being fine.
Myth: a two-stroke additive makes it safe to drive home. It is an old workaround, supposed for another issue. None of what petrol weakened gets put back by it — and afterwards, that tank still holds the petrol.
"Drain it yourself and you're sorted" — a myth, since after it's been running some petrol lies in the filter and lines, waiting to go straight back through your pump at your next start. Besides, petrol emptied into a can by the road is truly hazardous.
How it happens: petrol in a diesel
Nobody does it on purpose, and it is rarely carelessness. A diesel nozzle mostly won't go into a petrol vehicle, yet the slimmer petrol nozzle goes into the filler of a diesel nearly without resistance — so forecourts make this one error easy, and only in that direction.
When routine and the vehicle stop matching, it occurs. Hire cars, courtesy cars, and vehicles that are new to you. Two motors on one drive, one petrol, one diesel. A forecourt you know, but with its pumps laid out differently. Filling up in a rush on the way to Hackney Central, with a train to catch. A new-to-you diesel Renault Megane, its first fuelling, and a motorist used to petrol: exactly when it happens. Add a back seat full of kids, a phone call or rain, and habit wins.
Hackney people: how to prevent petrol in a diesel next time
- Not every forecourt in the UK keeps to green for unleaded and black for diesel, even if most usually do. Check the petrol pump's label; the colour is only a clue.
- In a motor you do not know, look inside the flap over your filler or at the cap before the first fill: plenty of cars state the fuel there.
- One of each in the home? Label the key to the diesel — a coloured fob, a sticker — because meaning to remember isn't enough.
- "Diesel", aloud, before you lift the nozzle — each time a new or hired car gets its first tank. It sounds silly. It works.
- Whilst you're thinking about something else, this is an easy mistake to make — so tuck the phone away.
- A misfuel inhibitor helps, up to a point. Some diesels come with a filler designed to block a petrol nozzle, and add-on devices exist for cars without one. They are a safety net, not a reason to stop checking the petrol pump.
- The moment you realise, stop: less petrol inside your tank makes a weaker mix. What to do next does not change, though — still don't start it.
Petrol already in a diesel around Hackney? Start here
Short and simple, then, is the order of things. Starting it is out, and so is switching on the ignition. Ask the attendants to help you push it clear of the pump if you are still on the forecourt, whether that is Valero or anywhere else. Phone 0333 366 0103 next, with three facts — your fuel, the approximate amount, and whether it has run.
If it was AdBlue instead of petrol, say so. That is a different problem — corrosion and deposits rather than lost lubrication — and it has its own page for Hackney.
Hackney petrol in a diesel jobs: why one costs more than another
There's no honest single quote for this, since the four scenarios above are four different jobs. Which of them you are in is mostly what moves the cost. Two things follow that: the petrol that went in as a share of what that tank takes, then the place the vehicle is in and whether a van can get to it safely.
What went in, how much, and whether it's run — three questions we ask before costing, not after, for precisely that reason. A range turns into a straight figure when the replies are in.
About Hackney
Hackney is a locality in East London, situated approximately 4 miles northeast of central London. Hackney sits at a low elevation of around 20 metres above sea level, and is characterized by a high proportion of flat dwellings. Hackney is close to nearby places such as Hackney Central, South Hackney, and Dalston, and is home to a diverse population of around 13,100 people. Hackney is also a short distance from the city of London, with the nearest point being around 2.6 miles away.
Across Greater London and in Hackney: fuel drain cover
Hackney Central, South Hackney and Dalston are among the places near Hackney that the same teams work, answering petrol in diesel jobs across Hackney's E postcode area. Our engineers drain wherever your vehicle is — your own driveway, a lay-by, a supermarket car park, a forecourt — so it never needs to come to us.
Still at the petrol pump in Hackney?
Then you're in the best place there can be. Leave the car turned off, and ring.