Kingsmead: Petrol in a Diesel Car? How Worried to Be
Provided it has not been started, you can worry less than you probably are. Till your ignition primes the pump, your starter cranks, or your car is driven, petrol in a diesel tank just sits there and does nothing. Which makes the honest reply to the first Kingsmead question — "have I wrecked it?" — usually no. Petrol in Diesel is who to call, with the engine kept off, and so it remains that way. The rest of this page sets out what petrol actually does to a diesel, how to tell how far it has got, and how to make sure it does not happen to you a second time.
What petrol in a diesel does to the engine
On its way through an engine, diesel does two jobs. Before it combusts, it lubricates — then it burns. The high-pressure pump and your injectors are designed to extremely fine tolerances, and your diesel passing through them is what stops those surfaces from wearing against one another.
The second task petrol does not do at all, and the first it does badly. 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 runnier than diesel, it strips out the protection the fuel system rests on, and any pump running on that mixture is wearing itself.
Combined, those leave the shape of the issue clear. Not contact but movement is what does the harm. Petrol in a tank is a fuel issue. Whatever a worn pump sheds travels on, carried by your fuel, into the injectors further along, which is why a pump that has worked on that petrol is where a mechanical fault starts.
Kingsmead, petrol in a diesel: four cases, from mild to serious
Filled but not once started — as good as it gets. Only your tank has petrol in it, and so the task is emptying that tank and rinsing the system where the car sits. This situation can only really occur on a forecourt: anywhere else, the car got there by being driven.
Started for a moment, or just the ignition on. Once primed, the system has drawn petrol out of that tank as far as the fuel filter and your lines. That is normally still an easy task — a drain, a flush, and the filter seen to.
Those few miles driven meant your pump labouring on fuel thinned by petrol throughout. Miles is only half of it; how hard it was driven counts just as much. Either way this work runs to your tank, the lines, the fuel filter and clean fuel through the whole system. A school run to Oldfield Park Infant School is one thing. Very different a second time: a trip to Bath, under a mile away, or some mileage on the M4, under 10 miles from Kingsmead, where the motor never stopped working hard.
Driven until it protested. Rattling, a lumpy idle, smoke, a throttle that has gone soft. The engine is telling you your fuel is no longer behaving like diesel. Leave it wherever it has stopped: a lay-by, a quiet street, the verge on Green Park. Permanent damage is very unusual when a vehicle is stopped quickly, and the drain and flush-through that still go first take care of it.
Petrol in a diesel stories Kingsmead drivers hear
Myth: "Fill it the rest of the way with diesel and it'll be fine." It will not. Topping up takes out nothing; it gives you a fuller tank of the same mix. A diesel fuel system doesn't accept petrol by percentage in the way that guidance presumes.
"Modern diesels can handle a little petrol" — a myth, and nearer the reverse. Smaller components and higher pressure are the way a modern diesel runs its fuel, and that makes the lubrication matter more, not less.
This is the one that catches drivers. Myth: "If it starts and drives, there's no damage done." Any petrol motor fed diesel usually will not run, and so the motorist stops and the damage stops with them. Feed petrol to a diesel and it usually starts, idles and pulls away as if nothing has happened — all the while its pump is wearing. Running is not the same as fine.
Myth: "Add some two-stroke oil and drive it home." It is an outdated fix for a separate fault. It doesn't put back what petrol has diluted, and the petrol is still in your tank afterwards.
The next start sends petrol back round the pump out of the lines and the filter, where some of that ends up once the engine has been run. That is why draining your tank yourself does not sort it — a myth. It is also truly risky to drain petrol into a can at the kerbside.
How it happens: petrol in a diesel
On purpose? Never. Through carelessness? Rarely, if ever. The petrol nozzle is the slimmer of the two and slips into a diesel filler with almost no resistance; a diesel nozzle generally will not go into a petrol vehicle at all. The forecourt makes it simple, and the error runs one way.
Routine and your car falling out of step is how it takes place. Hire cars, courtesy cars, and vehicles that are new to you. Households running one of each, petrol and diesel. The pumps in a different order on a familiar forecourt. A train to catch, and a rushed fill on the way to Bath Spa. Exactly the moment it occurs: after years of driving petrol, a driver fills a diesel Volkswagen Golf for the first time. With rain, a call arriving, or a car full of children to deal with, your hand just does what it has always done.
Kingsmead people: how to prevent petrol in a diesel next time
- Green for unleaded and black for diesel is normal in the UK — yet not on every forecourt. Go by the label on the pump, not the colour.
- The first fill in a new motor is the time to check the filler flap — on it, or on the cap, many cars state which fuel they take.
- Mark your key. In a household with one of each, a coloured fob or a sticker on the diesel's key does more than any amount of intending to remember.
- "Diesel", out loud, before you pick up the nozzle — every time a new or hired car gets its first tank. It sounds daft. It works.
- Thinking about something else is when this becomes an easy mistake to make, so put your phone away and keep your mind on the pump.
- Some diesels have a filler designed to reject a petrol nozzle, and devices you can add are available for motors without one. Such an inhibitor helps up to a point — as a backstop, not a reason to stop reading the petrol pump.
- Less petrol makes a thinner mixture, so stop as soon as you realise — while remembering that your next step is unchanged. It is still not to start the car.
Already put petrol in a diesel in Kingsmead?
The order of things is short, then. Starting it is out, and so is turning on your ignition. The staff on the forecourt — whether at Esso itself or wherever you filled up — will normally help roll it clear of the petrol pump if you ask. What got in, roughly how much, and whether it has run: tell us those when you phone 0333 366 0103.
Corrosion and deposits are the trouble with AdBlue, whereas petrol brings lost lubrication. So if it was AdBlue, say so — and read its own Kingsmead page.
Why one petrol in a diesel job around Kingsmead costs more than another
An honest single price doesn't exist here: four scenarios, four separate tasks. Which of them you're in is mostly what shifts the cost. Where the vehicle is matters too, and whether our van can safely get to it, after the ratio of petrol to what your tank holds.
Before any quote, not after, come three queries: your fuel that got in, its volume, and if it's run. That's why. A range turns into a straight figure when the answers are in.
About Kingsmead itself
Kingsmead is a suburban area located on the riverside in Somerset, with a relatively low elevation of 22 metres. Kingsmead sits adjacent to the city of Bath, with which it is closely associated, and is near other nearby places such as Westmoreland and Beechen Cliff. Kingsmead is characterized by a high proportion of flat housing, reflecting its urban setting. Kingsmead is also within easy reach of larger cities, being around 97 miles from London.
Across Somerset and around Kingsmead: fuel drain cover
Kingsmead rests in the BA postcode area, and the teams that answer petrol in diesel call-outs there work the places near it as well — Westmoreland, Bath and Beechen Cliff among them. A forecourt, a supermarket car park, a lay-by or your own drive are all places our technicians work, and the vehicle does not need to come to us.
In Kingsmead and still at the pump?
The best position there is, then — that is where you are. Keep it off. Ring.