Dodbrooke: Petrol in a Diesel Car? How Worried to Be
Probably less than you already are — provided nobody has started it. "Have I ruined it?" is the first question anyone around Dodbrooke asks, and the truthful answer is normally no, because petrol resting in a diesel tank hurts nothing until it's dragged through your 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. The rest of this page covers 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 again.
Inside the motor: what petrol in a diesel really does
Two tasks fall to diesel on its route round a motor. It burns, and before it burns it protects. Built to very fine clearances, the injectors and your pump depend on the diesel moving through them to keep their surfaces from wearing against one another.
The second job 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 precisely the reverse of what a diesel needs. On top of that it is thinner than diesel, it strips out the lubrication the system rests on, and any pump working on such a blend is wearing itself.
The shape of the problem is plain once you put those together. Not contact but circulation is what does the harm. Petrol in a tank is a fuel problem. After your pump has been running on that petrol, a mechanical problem has begun: anything shed by a pump that is grinding is carried downstream to the injectors with the fuel.
How serious is petrol in a diesel? Four scenarios we see around Dodbrooke
Fuelled up, never started. The best case there can be. On a forecourt, and really only there, that petrol is still confined to your tank — since everywhere else the car was driven to reach it. The job is draining and cleaning on the spot.
The ignition turned on, or a short start. With the fuel system primed, your lines and filter now hold petrol that came from that tank. Drain, flush, deal with your filter: still normally simple.
The pump now worked a couple of miles on diluted fuel — that's what driving the car does. How hard the car was driven counts as much as how far, and this work takes in your tank, the lines, the filter and fresh fuel through the entire circuit. On the school run to Kingsbridge Primary School, the mileage is short. Very different once more: a run to Plymouth, under 25 miles away, or some miles on the M5, under 50 miles from Dodbrooke, where the motor kept working hard.
Driven on till it complained — clattering, smoke, a lumpy idle, a soft throttle. That is your motor telling you its fuel no longer is behaving like diesel. Stop wherever you are — the verge on Church Street, a lay-by, a side street — and leave the vehicle where it is. Lasting damage is very unusual if a car is pulled over soon, and the drain and flush that still come first deal with it.
Myths Dodbrooke motorists hear about petrol in a diesel
It will not be fine. The myth: "Fill it the rest of the way with diesel and it will be." Nothing is removed by topping up — you are left with a bigger tank, still the same mix. Percentage isn't how a diesel fuel system tolerates petrol, whatever that guidance assumes.
Not so: a current diesel copes with a bit of petrol. Rather, the reverse. A modern diesel sends its fuel through more precise components at higher pressure, which makes the lubrication count more, not less.
Myth: "If it starts and drives, there's no harm done." This is the one that fools drivers. A petrol engine fed diesel normally will not run, and so the driver stops and the harm stops with them. A diesel fed petrol usually starts, ticks over and drives away as if nothing has happened, whilst your pump grinds. A running engine doesn't mean fine.
"A drop of two-stroke oil and drive it home" — a myth, taken from a fix from years ago, for a different fault. None of what petrol diluted gets put back by it — and afterwards, your tank still holds the petrol.
Myth: "Drain that tank yourself and you're sorted." After the engine has run, some of the petrol is no longer in the tank: it's in the fuel filter and your lines, and it goes straight back through your pump on the next start. It's also really hazardous to drain petrol into a can by the kerbside.
Why petrol in a diesel occurs so easily
Carelessness is seldom the cause, and nobody means to do it. A diesel nozzle mostly won't go into a petrol vehicle, but the narrower petrol nozzle goes into the filler of a diesel nearly without resistance — so forecourts make this one error simple, and only in one direction.
When routine and the vehicle stop matching, it takes place. Hire cars, courtesy cars, and vehicles that are new to you. One petrol and one diesel on the drive of the same household. Your ordinary forecourt, its pumps suddenly in a different order. A hurried fill en route to Ivybridge with a train to catch. A new-to-you diesel Renault Megane, its first fuelling, and a driver accustomed to petrol: precisely when it happens. With rain, a call coming in, or children to deal with, the hand simply does what it has always done.
Dodbrooke motorists: how to prevent petrol in a diesel next time
- Green for unleaded and black for diesel is usual in the UK — yet not on each forecourt. Go by the label on the pump, not the colour.
- In a car you do not know, look inside the flap over your filler or at the cap before the first fill: plenty of motors state the fuel there.
- A coloured fob or a sticker on your diesel's key achieves more than any amount of intending to remember, in a house with one of each.
- It sounds daft and it works: on your first fill in a new or hired car, say "diesel" aloud before you take the nozzle off the petrol pump.
- Tuck your phone away. This is an easy mistake to make while you're thinking about something else.
- Up to a point, a misfuel inhibitor helps: some diesels have a filler designed to refuse a petrol nozzle, and aftermarket devices are available for the remainder. Count it as a safety net, and keep checking the petrol pump.
- Stop the moment you notice. Less petrol inside that tank means a weaker mixture. It doesn't change what to do next, which is still not to fire it up.
Dodbrooke: already put petrol in a diesel?
The order of things is brief, then. Do not switch the ignition on, and do not start it. Ask the staff to help you roll it clear of the pump if you're still at the forecourt, whether that is Asda Express or anywhere else. What got in, roughly how much, and whether it's run: tell us that when you call 0333 366 0103.
Corrosion and deposits are the problem with AdBlue, whereas petrol means lost protection. So if it was AdBlue, say so — and read its own Dodbrooke page.
What makes one Dodbrooke petrol in a diesel job cost more than the next
An honest single price doesn't exist here: four scenarios, four separate jobs. The situation itself does most of the work of moving the cost. The share matters next, meaning how much of that tank is petrol, and then the location of the vehicle and whether getting to it is safe for our van.
That's why we ask three questions before quoting rather than after: what got in, how much, and if it's run. Those answers are what change a range into one firm number.
About Dodbrooke, for a moment
Dodbrooke is a suburban area situated on the banks of a river in Devon, with a mix of terraced housing and other residential properties. Dodbrooke lies near the towns of Kingsbridge and Westville, and is close to Ticket Wood, at an elevation of around 11 metres above sea level. Dodbrooke is located approximately 17 miles from Plymouth and 180 miles from London, making it a relatively small community in the South West region. Dodbrooke has a population of around 4539 people, living in a variety of homes, predominantly terraced in style.
Dodbrooke and Devon: where our fuel drain cover runs
Kingsbridge, Westville and Ticket Wood are among the locations around Dodbrooke that the same teams work, answering petrol in diesel calls across Dodbrooke's TQ postcode area. You need not bring the vehicle to us. Forecourts, supermarket car parks, lay-bys and your own drive are all places where we work.
At the pump in Dodbrooke, right now?
The best place there is, then — that is where you are. Switched off it stays; then ring.