Petrol in a Diesel Car in Falconwood: How Worried Should You Be?
If it has not been started, you can worry far less than you likely are. "Have I wrecked it?" is the first thing anyone in Falconwood asks, and the truthful answer is generally no, since petrol left in a diesel tank hurts nothing until it's dragged through your fuel system — by ignition priming, by your starter, or by being driven. Keep it like that: leave your engine off then phone Petrol in Diesel. The rest of this page explains what petrol actually does to a diesel, how to tell how far it has got, and how to make sure it does not happen to you again.
Inside the engine: what petrol in a diesel really does
Diesel does two jobs on its way through a motor. Before it burns, it protects — then it burns. The high-pressure pump and the injectors are designed to very fine gaps, and the diesel passing through them is what stops those surfaces from wearing down against each other.
Petrol handles the first job poorly and the second not at all. It is thinner than diesel and removes the lubrication your fuel system rests on, and so a pump running on a petrol mixture is a pump wearing itself. And petrol is made to resist igniting under compression, which is the opposite of what a diesel needs from its fuel. That's where the knocking comes from.
Together, those leave the shape of the problem clear. It is circulation that does the harm, not contact. All a tank with petrol in it amounts to is a fuel issue. A pump that has been running on that petrol is the beginning of a mechanical one, and whatever a worn pump sheds travels on with the fuel to the injectors downstream.
Four situations our technicians see in Falconwood: how bad is petrol in a diesel?
Filled up, and never started: no case is better. At a forecourt, and truly only there, that petrol is still confined to that tank — since everywhere else the car was driven to reach it. The task is draining and purging on the spot.
Started for a second, or only the ignition on. Once primed, the system has drawn petrol out of your tank as far as your filter and your lines. That's generally still a simple task — a drain, a flush, and your filter dealt with.
The pump has worked a couple of miles on weakened fuel — that's what driving the vehicle meant. How hard the vehicle was driven counts as much as how far, and this work takes in that tank, your lines, your filter and clean fuel through the whole system. Short trips, such as the school run to Bishop Ridley Church of England VA Primary School, are one matter. A run as far as London, under 10 miles away, is a very different task. So is any distance on the M20, under 10 miles from Falconwood, where the motor has been labouring hard the whole time.
Rattling, a lumpy idle, smoke, a throttle gone soft: driven till it complained. The motor is telling you your fuel is no longer behaving like diesel. Stop wherever you are — the verge on Northumberland Avenue, a lay-by, a side street — then leave the car there. Lasting damage is very unusual if a vehicle is stopped quickly, and the fuel drain and flush-through that still go first deal with it.
Stories Falconwood people hear about petrol in a diesel
"Top it up the rest of the way with diesel and it will be fine" — a myth. It won't. Nothing comes out when you top up — your tank simply holds more of the same mixture. The idea behind that guidance — that diesel fuel systems accept petrol by percentage — is wrong.
"Modern diesels can handle a little petrol" — a myth, and closer to the opposite. Smaller parts and higher pressure are how a current diesel runs its fuel, and that makes the protection count more, not less.
"It starts, it drives, so there is no harm" — the myth that catches most motorists than any other. Diesel in a petrol motor normally means a motor that won't run: the motorist stops, and so does the damage. A diesel fed petrol usually starts, ticks over and drives away as though nothing has happened, whilst the pump wears. Fine and running are not the same thing.
Myth: "Add some two-stroke oil and drive the vehicle home." It is an outdated workaround for a different fault. That petrol is still in your tank afterwards, and what it has weakened isn't put back.
Myth: "Drain the tank yourself and you are sorted." Once the engine has been run, some of that petrol is no longer in the tank: it's in the filter and the fuel lines, and it goes right back through your pump on the next start. Draining petrol into a can at the roadside is also truly dangerous.
How it happens: petrol in a diesel
It is seldom carelessness, and no one does it on purpose. The petrol nozzle is the slimmer of the two and slides into a diesel filler with almost no resistance; a diesel nozzle generally won't go into a petrol car at all. The forecourt makes it easy, and the mistake runs one way.
When routine and your car stop matching, it happens. Any car that is new to you — hired, on loan as a courtesy car, or brand new. One petrol and one diesel on the driveway of the same household. Your usual forecourt, its pumps suddenly in a different order. A train to catch, and a hurried fill en route to the nearest station. A new-to-you diesel Volkswagen Passat, its first fuelling, and a driver accustomed to petrol: precisely when it occurs. Throw in a back seat full of children, a phone call or rain, and habit takes over.
Next time you fill up in Falconwood: avoiding petrol in a diesel
- Check the petrol pump, not the colour. In the UK unleaded handles are normally green and diesel black, yet not on each forecourt. The label is what matters.
- Plenty of vehicles state the fuel inside the filler flap or on the cap, and so check there on the first fill in a car you do not know.
- Mark your key. In a house with one of each, a coloured fob or a sticker on your diesel's key does more than any amount of intending to remember.
- It sounds silly and it works: on the first fill in a new or hired car, say "diesel" aloud before you lift the nozzle off the petrol pump.
- While you are thinking about something else, this is an easy mistake to make — so put the phone away.
- Up to a point, a misfuel inhibitor helps: some diesels have a filler designed to reject a petrol nozzle, and aftermarket devices exist for the rest. Count it as a safety net, then keep checking the petrol pump.
- Less petrol makes a weaker mixture, so stop the moment you realise — while remembering that the next step is unchanged. It's still not to fire it up.
Put petrol in a diesel around Falconwood already?
The order of things is brief, then. Leave it unstarted, with your ignition off as well. Still on the forecourt, at Shell or anywhere else? Ask the staff to help you roll it away from the pump. Call 0333 366 0103 next, with three answers — your fuel, the rough amount, and if it's run.
Say so if it was AdBlue rather than petrol: it is a separate issue, with its own page for Falconwood, because AdBlue brings corrosion and deposits instead of lost lubrication.
One petrol in a diesel job in Falconwood costs more than another. Why?
The four situations above are four separate tasks, so no single price for this would be fair. Which of them you are in is chiefly what moves your cost. Next it's the share — how much petrol got in against how much your tank holds — and after that where the car is and whether a technician can reach it safely.
Three questions come first, before any quote, rather than after — what went in, how much, has it run — and that is the reason. Their answers are what turn a range into one firm number.
About Falconwood, briefly
Falconwood is a suburban area in southeast London, situated near the River Thames and close to the borders of Kent. Falconwood has a mix of housing types, but semi-detached homes are particularly prevalent in the area. Falconwood is located near several other suburban areas, including East Wickham, Welling, and Avery Hill, and is about 9.9 miles from central London.
Falconwood and Greater London: where our fuel drain cover runs
Our teams answering petrol in diesel jobs around Falconwood, in the DA postcode area, equally work the places near it, East Wickham, Welling and Avery Hill included. You need not move the vehicle to us. Forecourts, supermarket car parks, lay-bys and your own drive are all locations where we work.
Still at the pump around Falconwood?
No position is better: that's where you now are. Keep the car switched off, and ring.