Fordwich: Petrol in a Diesel Car? How Worried to Be
Provided it has not been started, you can worry far less than you probably are. Until the ignition primes the pump, your starter cranks, or the car is driven, petrol in a diesel tank simply rests there and does no harm. Which means the truthful reply to the first Fordwich question — "have I ruined it?" — usually no. To leave the vehicle like that, ring Petrol in Diesel then leave your engine switched off. The remainder of this page explains what petrol really does to a diesel, how to tell how far it has got, and how to make sure it doesn't happen to you a second time.
Petrol in a diesel: what does it do to the motor?
Two tasks fall to diesel on its route round a motor. Before it burns, it protects — then it combusts. What keeps the surfaces inside your high-pressure pump and the fuel injectors from grinding against each other is the diesel passing through them — they are designed to very fine clearances.
The second task petrol does not do at all, and the first it does poorly. The knocking comes from petrol being designed 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 depends on, and any pump running on that mixture is wearing itself.
Combined, those leave the shape of the issue clear. It is movement that does the damage, not contact. All a tank with petrol in it amounts to is a fuel issue. A pump that has been working on that petrol is the beginning of a mechanical one, and whatever a worn pump sheds travels on with the fuel to the injectors further on.
How serious is petrol in a diesel? Four situations our engineers see in Fordwich
The best case there can be: filled up, not once started. On a forecourt, and really only there, that petrol is still confined to your tank — because anywhere else the car was driven to get to it. The job is draining and purging on the spot.
Ignition on, or started for a second. Petrol has left the tank and reached your filter and the fuel lines, because the system has been bled. Normally little more than clearing, purging and sorting your filter, so still straightforward.
A couple of miles driven, and your pump has spent every one of them working on diluted fuel. Tank, lines, filter, then fresh fuel run through the entire circuit: that's the work, and the way your car was driven counts as much as the mileage. On the school run to Sturry Church of England Primary School, the mileage is short. Any distance on the M2, under 10 miles from Fordwich, means your engine has worked hard throughout, and a run to Canterbury, under 3 miles away, makes a very different job too.
Driven on until it protested — rattling, smoke, a lumpy idle, a soft throttle. What you are hearing is your engine reporting fuel that no longer runs like diesel. Whether it is the verge on High Street, a lay-by or a side street, stop where you are and leave it. The drain and flush still come first, and they take care of it: if a car is stopped soon, lasting damage is very unusual.
Stories Fordwich motorists hear about petrol in a diesel
Myth: topping up to full with diesel makes it fine. It does not. A bigger tank of the same mix is all it gives, since topping up removes nothing. The idea behind the advice — that diesel fuel systems tolerate petrol by percentage — is wrong.
If anything, the opposite holds. Myth: "A current diesel can cope with a bit of petrol." Smaller parts and higher pressure are the way a current diesel runs its fuel, and that makes the lubrication count more, not less.
This is the one that catches motorists. Myth: "If it starts and drives, there's no harm done." Diesel in a petrol motor generally means a motor that won't run: the driver stops, and so does the damage. Nothing seems to have happened when a diesel fed petrol fires up, ticks over and drives away, as it usually does; meanwhile your pump grinds. Running isn't the same as fine.
Not so: a two-stroke additive lets you to drive home. It was an old workaround, supposed for another fault. None of what petrol thinned is put back by it — and later, that tank still holds the petrol.
Once your engine has run, part of that petrol sits in the filter and your lines, not the tank — and your next start sends it right back through the pump. So the myth "drain the tank yourself and you're sorted" does not hold. And, a can of petrol drained at the roadside is genuinely hazardous.
How petrol ends up: petrol in a diesel
It is seldom carelessness, and no one does it on purpose. A diesel nozzle mostly will not go into a petrol motor, yet the narrower petrol nozzle goes into the filler of a diesel nearly without resistance — so forecourts make this one mistake straightforward, and just in one direction.
The moment routine stops matching the car is the moment it happens. Courtesy car, hire car, or a car that's brand new. One petrol and one diesel on the driveway of the same household. Your usual forecourt, its pumps now in a different order. A train to catch, and a hurried fill en route to Sturry. Precisely the moment it takes place: after years of driving petrol, a driver fills a diesel Volkswagen Golf for the first time. Your hand repeats what it has always done when you add rain, a phone call or a back seat full of children.
Next time you fill up around Fordwich: avoiding petrol in a diesel
- The label is what matters, and so check the petrol pump rather than the colour: in the UK unleaded handles are usually green and diesel black, yet not on every forecourt.
- In a motor you do not know, look inside the flap over your filler or at the cap before the first fill: many vehicles state the fuel type there.
- A coloured fob or a sticker on your diesel's key does more than any amount of intending to remember, for a household with one of each.
- "Diesel", out loud, before you lift the nozzle — every time a new or hired car needs its first tank. It seems daft. It works.
- Thinking about something else is when this becomes an easy mistake to make, so tuck the phone away then keep your mind on the petrol pump.
- Add-on devices are available for cars without one, and some diesels are built with a filler that won't accept a petrol nozzle. Helpful — but a backstop at best, never a reason to stop checking the label.
- The moment you notice, stop: less petrol inside your tank means a weaker mix. What to do next does not change, though — still do not fire it up.
Fordwich: already put petrol in a diesel?
Short and simple, then, is the order of things. Do not switch the ignition on, and do not start it. The staff at the forecourt — whether at Esso itself or wherever you filled up — will normally help roll it away from the pump if you ask. Next, 0333 366 0103. We will ask what went in, roughly how much, and if it's been run.
Say so if it was AdBlue instead of petrol: it is a different problem, with its own page for Fordwich, because AdBlue brings corrosion and deposits instead of lost protection.
One petrol in a diesel job around Fordwich costs more than another. Why?
A fair single price does not exist here: four scenarios, four separate jobs. Which of them you are in is mostly what shifts your cost. Where the car is matters too, and whether a van can safely get to it, after the share of petrol to what that tank holds.
What got in, how much, and if it has run — three queries we ask before quoting, not after, for exactly that reason. With the replies, there is a straight figure rather than a range.
About Fordwich, briefly
Fordwich is a small town situated on the lakeside in Kent, with a low elevation of around 5 metres. Fordwich lies close to the city of Canterbury, approximately 2.3 miles away, and is near other places such as Sturry and Westbere. Fordwich has a population of around 4791 people and predominantly consists of semi-detached housing. Fordwich is located within the South East region of England, about 56 miles from London.
Fuel drain cover across Kent, Fordwich included
Petrol in diesel jobs around Fordwich — part of the CT postcode area — go to teams that likewise cover the locations about it, Sturry, Scotland Hills and Westbere among them. Our engineers drain where your car is — your own driveway, a lay-by, a supermarket car park, a forecourt — so it does not have to come to us.
Still at the petrol pump around Fordwich?
Then you are in the best position there can be. Leave the car turned off, and ring.