Littlemore: Petrol in a Diesel Car? How Worried to Be
Likely less than you already are — as long as nobody has started the vehicle. Everyone around Littlemore starts with "have I ruined it?", and the honest answer is usually no: petrol left in your tank of any diesel remains harmless till priming, cranking or driving pulls it into your fuel system. Leave the motor off then ring Petrol in Diesel — that keeps it that way. Read on for three things: the effect petrol has inside a diesel motor, the signs of how far it has got, and ways to make sure you never do it again.
Petrol in a diesel: what does it do to the engine?
On its way through a motor, diesel does two tasks. Before it burns, it lubricates — and then it combusts. Your high-pressure pump and your injectors are designed to very fine gaps, and your diesel passing through them is what stops those surfaces from grinding against one another.
The second task petrol doesn't do at all, and the first it does poorly. A pump running on a petrol mix is wearing itself out, because petrol is runnier than diesel and strips out the protection the fuel system relies on. Petrol is also designed to resist igniting under compression — the opposite of what a diesel needs from its fuel — and that's where the clattering starts.
Together, those leave the shape of the trouble clear. It is circulation that does the damage, not contact. All a tank with petrol in it amounts to is a fuel problem. Whatever a worn pump sheds travels on, carried by your fuel, into the injectors downstream, which is why a pump that has worked on that petrol is where a mechanical fault begins.
How bad is petrol in a diesel? Four scenarios our engineers see in Littlemore
Fuelled, and not started: no case is better. The petrol is in that tank and just the tank, and the job is a drain and a flush where the vehicle stands. This is the one situation that can only truly take place at a forecourt, as anywhere else the vehicle has been driven to get there.
A moment's running, or just your ignition on. The system has been primed, so petrol has left your tank and got to your filter and the fuel lines. Drain, flush, see to the fuel filter: still normally straightforward.
The pump has spent a few miles on thinned fuel — that's what driving it does. Tank, lines, filter, then fresh fuel run through the whole circuit: that's this work, and the way the car was driven matters as much as the mileage. Short trips, like the school run to John Henry Newman Academy, are one thing. Very different again: a run to Oxford, under 3 miles away, or some miles on the Wheatley Spur, under 10 miles from Littlemore, where your engine never stopped working hard.
Driven till it protested. Rattling, a ragged idle, smoke, a throttle that has gone soft. That is your motor telling you its fuel has stopped behaving like diesel. Leave it where it has stopped: a lay-by, a quiet street, the verge on Cowley Road. A car stopped soon very seldom has permanent damage, since the drain and the flush, which still go first, deal with it.
Myths Littlemore people hear about petrol in a diesel
Myth: "Fill it the rest of the way with diesel and it will be fine." It will not. Nothing comes out when you top up — your tank just carries more of the same mixture. A diesel fuel system does not tolerate petrol by percentage in the way that guidance assumes.
"Current diesels can handle a little petrol" — a myth, and nearer the reverse. A newer diesel sends its fuel through finer components at higher pressure, which makes the protection matter more, not less.
"It starts, it drives, so no harm done" — the myth that catches most motorists than any other. Feed diesel to a petrol engine and it generally will not run, so the driver stops — and the harm stops with them. Feed petrol to a diesel and it generally fires up, ticks over and pulls away as if nothing has happened — all the while its pump wears. Running is not the same as fine.
An outdated fix for a different fault is behind this one. Myth: "Add some two-stroke oil and drive it home." None of what petrol diluted is put back by it — and afterwards, your tank still holds the petrol.
Myth: "Drain that tank yourself and you're sorted." Once the engine has run, some of the petrol is no longer inside your tank: it is in the fuel filter and your lines, and it goes right back through your pump on your next start. Clearing petrol into a can by the kerbside is also truly dangerous.
How does petrol in a diesel take place?
Nobody does it on purpose, and it is seldom carelessness. A diesel nozzle generally won't go into a petrol vehicle, yet the narrower petrol nozzle goes into the filler of a diesel almost without resistance — so forecourts make this one mistake easy, and only in one direction.
The moment routine stops matching the vehicle is the moment it happens. A new vehicle, a hire car or a courtesy car. One petrol and one diesel on the driveway of the same household. A forecourt you know, but with its pumps arranged differently. Fuelling up in a hurry en route to Radley, with a train to catch. Exactly the moment it happens: after years of driving petrol, someone fills a diesel Skoda Octavia for the first time. With rain, a call coming in, or a car full of children to deal with, the hand simply does what it always has.
Avoiding petrol in a diesel next time you fill up around Littlemore
- Not every forecourt in the UK follows green for unleaded and black for diesel, though most usually do. Read the pump's label; the colour is just a clue.
- In a car you do not know, look inside the flap over your filler or at the cap before the first fill: many vehicles print the fuel type there.
- Good intentions do less than a sticker or a fob in a bright colour on your diesel's key if a house has one of each. So mark it.
- Before the nozzle comes off the petrol pump the first time you fuel a hired or new car, say "diesel" out loud. Silly, perhaps, but it works.
- While you are thinking about something else, this is an easy mistake to make — so tuck your 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 are available for cars without one. They are a safety net, not a reason to stop reading the pump.
- Less petrol means a weaker mixture, and so stop the moment you realise — though remembering that your next stage is unchanged. It's still not to fire it up.
Littlemore: already put petrol in a diesel?
The order of things is short, then. Never crank it, and do not turn the ignition on. If you're still at the forecourt — Sainsbury's or anywhere else — ask the staff to help you push the car away from the pump. What was put in, roughly how much, and whether it's run: tell us those when you phone 0333 366 0103.
AdBlue, not petrol? Then say so. Corrosion and deposits, not lost protection, make it a different problem — Littlemore has a page just for it.
Why one petrol in a diesel job around Littlemore costs more than another
Four separate jobs lie behind the four scenarios above — which is why there is no honest single quote. What moves your cost is mostly which of them you are in. The share counts next, meaning how much of the tank is petrol, and then the position of the vehicle and whether reaching it is safe for our van.
That's why we ask three questions before costing rather than after: what got in, how much, and if it's run. Those replies are what turn a range into one firm number.
About Littlemore
Littlemore is a suburban area located on the River Thames, approximately 2.6 miles from Oxford city centre. Littlemore sits at an elevation of 72 metres, with semi-detached housing being the predominant type of accommodation in the area. Littlemore is close to nearby places such as Rose Hill, Iffley, and Sandford-on-Thames, and is situated within the South East region of England. Littlemore has a population of around 8585 people and is about 49.2 miles from London.
Across Oxfordshire and around Littlemore: fuel drain cover
The teams answering petrol in diesel calls in Littlemore, in the OX postcode area, also work the spots near it, Rose Hill, Iffley and Sandford-on-Thames among them. You need not move your car to us. Forecourts, supermarket car parks, lay-bys and your own driveway are all locations we drain.
In Littlemore and still at the pump?
Then, you could not be in a better spot. Keep it off. Ring.