How Worried Should You Be? Petrol in a Diesel Car in South Kensington
Probably less than you are now — provided no one has started the car. "Have I wrecked it?" is the first thing everyone around South Kensington asks, and the truthful answer is generally no, since petrol resting in a diesel tank harms nothing till it's dragged through the fuel system — by ignition priming, by your starter, or by being driven. Leave the engine off and phone Petrol in Diesel — that keeps it like that. Further down, you will find what petrol actually does inside a diesel, how far it may have got, and how to stop it happening to you again.
Petrol in a diesel: what does it do to the engine?
On its way through a motor, diesel has two tasks. It lubricates first, and after that does it burn. Your high-pressure pump and the fuel injectors are built to extremely fine gaps, and the diesel passing through them is what stops those surfaces from wearing against one another.
Of these two jobs, petrol handles the first badly and the second not at all. It's thinner than diesel and removes the lubrication your fuel system rests on, and so a pump running on a petrol mix is a pump wearing itself. And petrol is made to resist igniting under compression, which is the opposite of what a diesel needs from its fuel. That's where the clattering comes from.
Put those together and the shape of the issue is plain. The damage is done by movement, not by contact. Where that petrol is only inside the tank, it's a fault of fuel, nothing more. After the pump has been labouring on that petrol, a mechanical issue has started: whatever is shed by a pump that's wearing down travels downstream to the injectors with the fuel.
Petrol in a diesel around South Kensington: how bad is it? Four cases
The best case there is: filled up, not once started. Being on a forecourt is what makes this the case: elsewhere, your car has been driven there to begin with. With that petrol held in the tank alone, it is drained and cleaned on the spot, and nothing more is needed.
Ignition on, or started for a second. Once primed, the system has pulled petrol out of your tank up to the fuel filter and your lines. That's generally still a simple task — a drain, a flush, and your filter seen to.
Driven a couple of miles. Now the pump has spent those miles running on diluted fuel. How hard the vehicle was driven counts as much as how far, and the work covers the tank, the lines, your filter and fresh fuel through the whole system. On the school run to Our Lady of Victories RC Primary School, the mileage is short. A run as far as Westminster, under 3 miles away, is a very different task. So is any mileage on the M4, under 5 miles from South Kensington, where the engine has been running hard throughout.
Driven on until it protested — knocking, smoke, a lumpy idle, a dead throttle. What you are hearing is the engine reporting fuel that no longer behaves like diesel. Stop where you are — on the verge on Clareville Street, at the kerb, down a side road — and don't move it. The drain and flush-through still go first, and they deal with it: when a car is stopped quickly, long-term damage is very uncommon.
Petrol in a diesel stories South Kensington people hear
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 it gives, because topping up removes nothing. Percentage isn't how a diesel fuel system copes with petrol, whatever that guidance supposes.
If anything, the reverse is true. Myth: "A current diesel can cope with a bit of petrol." More precise parts and higher pressure are the way a modern diesel runs its fuel, and that makes the lubrication matter more, not less.
"It starts, it drives, so there is no harm" — the myth that trips up most drivers than any other. The driver of a petrol engine fed diesel usually has no choice but to stop, because it will not run, and the harm stops there. A diesel fed petrol normally starts, idles and drives away as though nothing has happened, whilst your pump wears. Being able to run is not proof of being fine.
"A drop of two-stroke oil and drive it home" — a myth, borrowed from a fix from years ago, for a distinct issue. None of what petrol weakened gets put back by it — and afterwards, the tank still contains the petrol.
Once your engine has been run, part of that petrol is in the filter and your lines, not your tank — and your next start pulls it straight back through the pump. So the myth "drain the tank yourself and you are sorted" doesn't stand up. On top of that, petrol cleared into a can by the road is truly dangerous.
How does petrol in a diesel occur?
No one does it on purpose, and it is rarely carelessness. One way only, since of the nozzles: the slimmer petrol one slips inside a diesel filler with almost no resistance, while the diesel one mostly won't fit a petrol motor. That's how the forecourt makes it easy.
The moment habit stops matching the vehicle is the moment it occurs. Courtesy car, hire car, or a vehicle that is new. A household with one petrol and one diesel on the drive. A forecourt you know, only with its pumps arranged differently. A hurried fill en route to West Brompton with a train to catch. Years of petrol motors behind you, a diesel Renault Megane in front of you on the forecourt for its first tank — that's when. With rain, a call arriving, or a car full of children to deal with, the hand simply does what it has always done.
How to avoid petrol in a diesel on your next fill-up in South Kensington
- The label is what counts, so read the pump instead of the colour: in the UK unleaded handles are normally green and diesel black, but not on each forecourt.
- In a car you don't know, look inside the flap over your filler or at the cap before the first fill: plenty of cars state the fuel type there.
- One of each in the house? Mark your key to the diesel — a coloured fob, a sticker — since intending to remember isn't enough.
- Before the nozzle comes off the pump the first time you fill a hired or new vehicle, say "diesel" out loud. Silly, yes, yet it does the trick.
- Mistakes like this are straightforward to make while your mind is on something else, so the phone goes away.
- Some diesels come with a filler designed to refuse a petrol nozzle, and devices you can add exist for cars without one. Such an inhibitor helps up to a point — as a safety net, not a reason to stop reading the petrol pump.
- Less petrol makes a weaker blend, and so stop the moment you realise — though remembering that your next stage is unchanged. It is still not to fire it up.
Put petrol in a diesel around South Kensington already?
The order of things is short, then. Leave it unstarted, with the ignition switched off as well. Yet at the forecourt, at Shell or anywhere else? Ask the attendants to help you push the car clear of the petrol pump. Then ring 0333 366 0103 and tell us what got in, about how much, and whether it has run.
Say so if it was AdBlue rather than petrol: it's a different fault, with its own page for South Kensington, since AdBlue brings corrosion and deposits instead of lost protection.
What makes one South Kensington petrol in a diesel task cost more than the next
The four situations above are four different jobs, so no single price for this would be honest. Mostly, the cost shifts with which one you're in. Where your car is counts too, and whether a technician can safely reach it, after the ratio of petrol to what your tank holds.
That is why we ask three questions before costing rather than after: what went in, how much, and whether it has run. Those answers change a range into a straight figure.
About South Kensington itself
South Kensington is a densely populated suburban area in central London, situated approximately 2.5 miles from the city centre. South Kensington sits near the Thames, at a low elevation of around 14 metres, and is bordered by nearby places such as Brompton and Knightsbridge. South Kensington is predominantly composed of flat dwellings, accommodating a sizable population of around 19,509 residents. South Kensington is also close to Westminster, being only 2.4 miles away from the city.
Across Greater London and in South Kensington: fuel drain cover
Petrol in diesel jobs around South Kensington — part of the SW postcode area — go to vans that likewise cover the locations round it, Brompton, West Brompton and Knightsbridge among them. We drain where your vehicle is — your own driveway, a lay-by, a supermarket car park, a forecourt — so it does not have to come to us.
South Kensington: still at the pump?
The best place there is, then — that is where you are. Keep the car switched off, and ring.