How Worried Should You Be? Petrol in a Diesel Car in Madron
Provided it has not been started, you can worry far less than you likely are. Till your ignition primes the pump, the starter turns, or your car is driven, petrol in a diesel tank just rests there and does nothing. Which makes the truthful reply to the first Madron question — "have I ruined it?" — usually no. Leave the motor off then phone Petrol in Diesel — that keeps it like that. The remainder of this page sets out 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.
The motor and petrol in a diesel: what happens
Two tasks fall to diesel on its route round a motor. It protects to begin with, and after that does it burn. Designed to very fine clearances, the injectors and your pump rely on your diesel flowing through them to keep their surfaces from wearing against one another.
Of these two jobs, petrol handles the first badly and the second not at all. The rattling 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 system rests on, and any pump running on such a mixture is wearing itself.
Seen together, they show the shape the issue has. The harm is done by circulation, not by contact. Any tank with petrol in it is a fuel issue. Whatever a worn pump sheds goes on, borne by your fuel, into the injectors downstream, which is why a pump that has worked on that petrol is where a mechanical issue starts.
Petrol in a diesel in Madron: how bad is it? Four situations
Fuelled but not once started — the best it gets. That petrol is inside the tank and just the tank, and the task is a drain and a flush where the car sits. This is the one situation that can only really happen on a forecourt, since anywhere else the vehicle has been driven to get there.
The ignition switched on, or a brief start. Your system has been bled, and so petrol has left the tank and got to your filter and your lines. Normally little more than clearing, flushing and seeing to your filter, and so still easy.
The pump has spent a few miles on diluted fuel — that is what driving the car meant. Mileage is only half of it; how hard it was driven matters equally. Either way the work runs to that tank, the fuel lines, the fuel filter and fresh fuel through the whole circuit. On the school run to Madron Daniel CofE (VA) School, the distance is small. A run as far as Truro, under 25 miles away, is a very different task. So is any miles on the M5, over 50 miles from Madron, where the motor has been labouring hard the whole time.
Driven on till it complained — rattling, smoke, an uneven idle, a soft throttle. The fuel isn't acting like diesel any more, and the motor is telling you. Whether it's the verge on Trelawney Estate, a lay-by or a side street, stop there then leave it. What goes first is still the drain and flush-through, and that sorts it out, with lasting damage very rare if a car is pulled over early.
What Madron drivers get told about petrol in a diesel — and the myths in it
Myth: topping up to full with diesel makes it fine. It doesn't. Nothing is removed when you top up — that tank just carries more of the same mixture. Percentage is not how a diesel fuel system tolerates petrol, however much that guidance assumes.
Myth: "A newer diesel can cope with a bit of petrol." If anything, the reverse. A modern diesel runs its fuel through more precise parts at higher pressure, which makes the lubrication count more, not less.
"It starts, it drives, and so no harm done" — the myth that catches most people than any other. A petrol engine fed diesel usually will not run, so the driver stops and the damage stops with them. A diesel fed petrol usually starts, ticks over and drives away as if nothing has happened, whilst your pump grinds. Fine and running are not the same thing.
Myth: "Add some two-stroke oil and drive it home." It's an old fix for a distinct fault. What petrol has thinned remains thinned, and the petrol stays inside the tank regardless.
Myth: "Drain that tank yourself and you're sorted." Once your engine has been run, some of the petrol is no longer in that tank: it is in the filter and the fuel lines, and it goes straight back through the pump on the next start. It's also really dangerous to drain petrol into a can by the kerbside.
Why petrol in a diesel happens at all
It is rarely carelessness, and no one does it on purpose. The forecourt makes it simple: the petrol nozzle is the narrower of the two, and it slips into a diesel filler with almost no resistance, while a diesel nozzle mostly will not go into a petrol motor at all. So the mistake runs one way.
When routine and your car stop matching, it occurs. Any motor that is new to you — hired, on loan as a courtesy car, or brand new. Households running one of each, petrol and diesel. A forecourt you know, but with its pumps laid out differently. A train to catch, and a hurried fill on the way to Penzance. Exactly the moment it takes place: after years of driving petrol, a driver fills a diesel Volkswagen Passat for the first time. With rain, a call arriving, or children to deal with, the hand just does what it has always done.
Madron people: how to avoid 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.
- Inspect your filler flap. Many vehicles state the fuel type inside the flap or on the cap. Look at it on your first fill in any car you don't know.
- One of each in the household? Label your key to your diesel — a coloured fob, a sticker — since meaning to remember is not enough.
- It sounds daft and it does the trick: on your first fill in a new or hired car, say "diesel" out loud before you take the nozzle off the petrol pump.
- While you're thinking about something else, this is an easy mistake to make — so put the phone away.
- Some diesels have a filler designed to block a petrol nozzle, and devices you can add exist for vehicles without one. Such an inhibitor helps up to a point — as a safety net, not a reason to stop reading the pump.
- Noticing it halfway? Stop at once. A thinner mix follows from less petrol in the tank, yet your next stage stays the same: do not start the vehicle.
Madron: already put petrol in a diesel?
Short and simple, then, is the order of things. Never fire it up, and don't turn the ignition on. Yet on the forecourt, at Texaco or anywhere else? Ask the attendants to help you push it away from the pump. What was put in, about how much, and whether it's run: tell us that when you ring 0333 366 0103.
Say so if it was AdBlue instead of petrol: it is a different problem, with its own page for Madron, because AdBlue brings corrosion and deposits instead of lost lubrication.
Madron petrol in a diesel jobs: why one costs more than another
An honest single price doesn't exist here: four situations, four separate tasks. Mostly, the cost moves with which one you're in. Two things follow that: the petrol that was put in as a proportion of what your tank takes, then the spot your car is in and whether a van can get to it safely.
What was put in, how much, and whether it has run — three queries our engineers ask before costing, not after, for exactly that reason. With the replies, there is a straight figure rather than a range.
About Madron and where it is
Madron is a small village in Cornwall, situated on the coastal side of the Penwith peninsula, with an elevation of around 127 metres. Madron lies near several nearby settlements, including Heamoor, Boswarthen, and Tremethick Cross, and is approximately 24 miles from the city of Truro. Madron has a population of around 664 people, predominantly living in semi-detached housing. Madron is also relatively distant from London, at around 256 miles away.
Across Cornwall and around Madron: fuel drain cover
Heamoor, Boswarthen and Tremethick Cross are among the locations around Madron that the same teams work, answering petrol in diesel call-outs across Madron's TR postcode area. No need to bring the car to us. Forecourts, supermarket car parks, lay-bys and your own driveway are all locations where we work.
Madron: still at the pump?
The best position there is, then — that's where you are. Keep it off. Phone.