How Worried Should You Be? Petrol in a Diesel Car in Chalkwell
If it has not been started, worry less than you probably are. Petrol sitting in a diesel tank does nothing to your motor until something draws it through the system — the ignition priming the pump, your starter, or the drive itself. So the honest answer to the first query anyone around Chalkwell asks, "have I wrecked it?", is normally no. Keep it like that: leave your motor off and phone Petrol in Diesel. The rest of this page explains what petrol actually does to a diesel, how to judge how far it has got, and how to make sure it doesn't happen to you again.
The engine and petrol in a diesel: what happens
On its way through an engine, diesel does two tasks. Before it combusts, it protects — and then it combusts. What keeps the surfaces inside the high-pressure pump and the injectors from wearing down against one another is your diesel passing through them — they're made to very fine gaps.
Badly at the first, not at all at the second: that is petrol. A pump working on a petrol mix is wearing itself out, because petrol is runnier than diesel and takes away the lubrication the fuel system depends on. Petrol is also made to resist igniting under compression — the reverse of what a diesel wants from its fuel — and that's where the clattering comes.
Taken together, they make clear the shape the trouble has. The harm is done by movement, not by contact. Where the petrol is only inside the tank, it's a fault of fuel, nothing more. The beginning of a mechanical problem is a pump that has been working on that petrol — and whatever a worn pump sheds moves on with your fuel to the fuel injectors beyond it.
Four scenarios our engineers see around Chalkwell: how serious is petrol in a diesel?
Filled up, and never started: no case is better. The petrol is in the tank and only the tank, and the task is a drain and a flush where your car stands. This is the one situation that can only truly occur on a forecourt, because anywhere else the car has been driven to get there.
The ignition turned on, or a short start. Petrol has come out of the tank and got to your filter and the fuel lines, because your system has been bled. That is generally still a straightforward job — a drain, a flush, and the filter seen to.
Those few miles driven meant the pump working on fuel weakened by petrol the whole way. Tank, lines, filter, then fresh fuel run through the entire circuit: that's this work, and the way the car was driven counts as much as the distance. Short trips, like the school run to Westlands Primary School, are one matter. A run as far as Southend-on-Sea, under 15 miles away, is a very different job. So is any mileage on the M2, under 3 miles from Chalkwell, where the engine has been running hard the whole time.
It complained, and only then stopped: smoke, knocking, a throttle gone soft, an idle gone lumpy. The fuel isn't behaving like diesel any more, and your motor is saying so. Pull up wherever you are — the verge on Staplehurst Road, a lay-by, a side street — then leave it there. The drain and flush still go first, and they take care of it: when a car is stopped quickly, permanent damage is very rare.
Chalkwell motorists and that petrol in a diesel stories they hear
"Top it up the rest of the way with diesel and it will be fine" — a myth. It won't. Topping up removes nothing; it gives you a fuller tank of the same mixture. Percentage isn't how a diesel fuel system tolerates petrol, however much that guidance assumes.
If anything, the opposite holds. Myth: "A modern diesel can cope with a bit of petrol." Lubrication matters more on modern diesels, not less, since their fuel passes through more precise parts at higher pressure.
The myth that catches drivers off guard: if it starts and drives, it must be unharmed. The motorist of a petrol motor fed diesel usually has no choice but to stop, since it will not run, and the damage stops there. A diesel fed petrol usually starts, idles and drives away as if nothing has happened, whilst your pump grinds. Running is not the same as fine.
Myth: "Add some two-stroke oil and drive the car home." It's an outdated fix for a different problem. None of what petrol thinned gets put back by it — and afterwards, the tank still contains the petrol.
"Drain it yourself and you are sorted" — a myth, since after it's been running some petrol sits in your filter and lines, waiting to go right back through your pump on the next start. On top of that, petrol cleared into a can by the road is genuinely hazardous.
How does petrol in a diesel occur?
Nobody does it on purpose, and it's seldom carelessness. A diesel nozzle generally won't go into a petrol car, but the smaller petrol nozzle goes into the filler of a diesel nearly without resistance — so forecourts make this one mistake straightforward, and only in one direction.
The moment habit stops matching the car is the moment it happens. Courtesy car, hire car, or a vehicle that's new. One petrol and one diesel on the drive of the same household. Your usual forecourt, its pumps suddenly in a different order. Fuelling up in a rush on the way to Sittingbourne, with a train to catch. The first fill-up in a diesel Volkswagen Passat after years of driving petrol is precisely the moment it takes place. Add rain, a phone call or a back seat full of children, and your hand does what it has always done.
Next time you fill up around Chalkwell: avoiding petrol in a diesel
- Green for unleaded and black for diesel is normal in the UK — but not on every forecourt. Trust the label on the petrol pump, not the colour.
- Check your filler flap. Plenty of cars state the fuel inside the flap or on the cap. Look at it on the first fill in a vehicle you don't know.
- Good intentions count for less than a sticker or a fob in a bright colour on your diesel's key when a household has one of each. So mark it.
- "Diesel", out loud, before you pick up the nozzle — every time a new or hired car needs its first tank. It sounds daft. It does the trick.
- Thinking about something else is when this becomes an easy mistake to make, so tuck the phone away and keep your mind on the petrol pump.
- A misfuel inhibitor helps, up to a point. Some diesels come with a filler designed to reject a petrol nozzle, and add-on devices exist for motors without one. They are a safety net, not a reason to stop reading the pump.
- As soon as you realise, stop: less petrol in that tank makes a thinner blend. What to do next doesn't change, though — still don't crank it.
Petrol already in a diesel in Chalkwell? Start here
Then the order of things is brief. Starting it is out, and so is turning on your ignition. The attendants at the forecourt — whether at Esso itself or wherever you filled up — will usually help roll it clear of the petrol pump if you ask. Then ring 0333 366 0103 and tell us what was put in, roughly how much, and whether it's run.
AdBlue, not petrol? Then tell us. Corrosion and deposits, not lost lubrication, make it a different fault — Chalkwell has a page just for it.
Chalkwell petrol in a diesel tasks: why one costs more than another
Four separate tasks lie behind the four scenarios above — which is why there's no honest single quote. Which of them you are in is mostly what moves your cost. Where the car is matters too, and whether a technician can safely get to it, after the share of petrol to what that tank takes.
Ahead of any quote, not after, we ask three questions: the fuel that went in, the volume, and whether it has run. That is why. The answers change a range into a straight figure.
About Chalkwell
Chalkwell is a suburban area in Kent, situated on the coast near the mouth of the Thames estuary. Chalkwell has a relatively low elevation of 22 metres and is located approximately 38 miles from London. Chalkwell is characterized by its semi-detached housing stock and is close to nearby places such as Grove Park and Key Street. Chalkwell is also near the town of Sittingbourne and the city of Southend-on-Sea, which is 13.5 miles away.
Across Kent and around Chalkwell: fuel drain cover
Chalkwell sits in the ME postcode area, and our teams that answer petrol in diesel calls there work the spots near it as well — Grove Park, Key Street and Sittingbourne among them. Our engineers drain wherever your car is — your own drive, a lay-by, a supermarket car park, a forecourt — so it does not have to come to us.
Chalkwell: still at the petrol pump?
In that case, you could not be in a better place. Phone, and keep it switched off.