Petrol in a Diesel Car in South Darenth: How Worried Should You Be?
Probably less than you already are — as long as nobody has started it. Everyone in South Darenth starts with "have I wrecked it?", and the fair answer is generally no: petrol resting inside that tank of a diesel remains harmless until priming, cranking or driving draws it into the fuel system. To leave the vehicle that way, call Petrol in Diesel then leave the engine alone. 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 does not happen to you again.
The engine and petrol in a diesel: what happens
Passing through an engine, diesel is doing two jobs at once. It burns, and before it burns it lubricates. The high-pressure pump and the fuel injectors are designed to extremely fine clearances, and your diesel passing through them is what stops those surfaces from wearing against one another.
Badly at the first, not at all at the second: that is petrol. Being less viscous than diesel, petrol strips away the protection a fuel system needs, so a pump on the mixture to wear itself. It is also made to resist igniting under compression — the reverse of what a diesel needs — which is where you hear the knocking.
Put those together and the shape of the trouble is clear. It's movement that causes the harm, not contact. Petrol in the tank is a fuel issue. A pump that has been labouring on that petrol is the beginning of a mechanical one, and whatever a worn pump sheds moves on with your fuel to the fuel injectors downstream.
How serious is petrol in a diesel? Four scenarios our engineers see around South Darenth
Filled up, and never started: no case is better. Being at a forecourt is what makes this the case: elsewhere, the car has been driven there to begin with. With that petrol held inside that tank alone, it's drained and cleaned on the spot, and nothing more is needed.
Ignition on, or started for a moment. The fuel system has been bled, and so petrol has left that tank and got to the filter and the fuel lines. Drain, flush, deal with the filter: still usually straightforward.
Those few miles driven were the pump running on fuel thinned by petrol the whole way. Mileage is only half of that; how hard it was driven counts just as much. Either way the work runs to the tank, the lines, the fuel filter and clean fuel through the entire system. The school run to Horton Kirby Church of England Primary School is one matter. Getting as far as London, under 25 miles away, makes a very different task — as does any distance on the M25, under 3 miles from South Darenth, with the motor working hard the whole time.
Driven till it complained. Rattling, an uneven idle, smoke, a throttle that has gone soft. The motor is telling you the fuel is no longer acting like diesel. Leave it where it has stopped: a lay-by, a side street, the verge on Holmesdale Road. Long-term damage is very uncommon when a car is pulled over quickly, and the fuel drain and flush that still come first sort it out.
What South Darenth drivers get told about petrol in a diesel — and the myths in it
"Top it up the rest of the way with diesel and it will be fine" — a myth. It won't. Topping up takes out nothing; it gives you a bigger tank of the same mix. Percentage is not how a diesel fuel system tolerates petrol, whatever that advice presumes.
Myth: a current diesel copes with a bit of petrol. If anything, the opposite. A newer diesel sends its fuel through smaller components at higher pressure, which makes the protection count more, not less.
This is the one that catches motorists. Myth: "If it starts and drives, there is no damage done." The motorist of a petrol engine fed diesel usually has no choice but to stop, since it will not run, and the damage stops with them. A diesel fed petrol normally starts, idles and drives away as if nothing has happened, while the pump wears. Fine and running are not the same at all.
"A drop of two-stroke oil and drive it home" — a myth, borrowed from a fix from years ago, for a separate issue. None of what petrol weakened is put back by it — and later, that tank still contains the petrol.
If the engine has run, part of that petrol is in the fuel filter and the fuel lines, not your tank — and the next start sends it straight back through your pump. So the myth "drain your tank yourself and you are sorted" does not stand up. It's also really dangerous to drain petrol into a can by the roadside.
Why petrol in a diesel occurs at all
It's seldom carelessness, and nobody does it on purpose. The petrol nozzle is the slimmer of the two and slips into a diesel filler with almost no resistance; a diesel nozzle generally won't go into a petrol motor at all. The forecourt makes it easy, and the error runs one way.
When routine and your car stop matching, it happens. Any vehicle that's new to you — hired, on loan as a courtesy car, or brand new. A household with one petrol and one diesel on the drive. The pumps in a different order on a well-known forecourt. Fuelling up in a rush en route to Farningham Road, with a train to catch. A new-to-you diesel Volkswagen Passat, its first fuelling, and a driver used to petrol: exactly when it happens. Your hand does what it has always done when you add rain, a phone call or a back seat full of children.
How to prevent petrol in a diesel on your next fill-up around South Darenth
- The label is what counts, so read the petrol pump instead of the colour: in the UK unleaded handles are normally green and diesel black, yet not on every forecourt.
- Check your filler flap. Many motors state the fuel inside the flap or on the cap. Look at it on your first fill in a vehicle you don't 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 meaning to remember.
- Before the nozzle leaves the petrol pump the first time you fuel a hired or new vehicle, say "diesel" out loud. Daft, yes, yet it does the trick.
- Mistakes like this are straightforward to make while your mind is on something else, so your phone goes away.
- A misfuel inhibitor helps, up to a point. Some diesels have a filler built to reject a petrol nozzle, and add-on devices are available for cars without one. They are a safety net, not a reason to stop checking the petrol pump.
- Noticing it mid-fill? Stop at once. A thinner blend results from less petrol inside your tank, yet the next stage stays the same: don't fire it up.
Petrol already in a diesel in South Darenth? Start here
Then, there is only a short order of things. Don't crank it, and don't turn the ignition on. Still on the forecourt, at Harvest Energy or anywhere else? Ask the staff to help you roll the vehicle away from the petrol pump. Next, 0333 366 0103. We'll ask what was put in, about how much, and if it's been run.
Corrosion and deposits are the trouble with AdBlue, where petrol brings lost protection. So if it was AdBlue, say so — and see its own South Darenth page.
Why one petrol in a diesel job around South Darenth costs more than another
Four separate tasks sit behind the four scenarios above — which is why there is no fair single quote. Chiefly, the cost shifts with which one you are in. Two things come after that: the petrol that was put in as a share of what your tank takes, then the place the car is in and whether a van can reach it safely.
Three queries come first, before any quote, instead of after — what was put in, how much, has it run — and this is the reason. The answers turn a range into a straight figure.
About South Darenth
South Darenth is a village situated on the River Darent in Kent, with a mix of terraced housing and other residential properties. South Darenth sits at an elevation of around 24 metres, close to the nearby villages of St Margarets, Sutton at Hone, and Horton Kirby. South Darenth is located near the southern outskirts of London, approximately 17.7 miles from the city centre. South Darenth has a population of around 2509 people, living in a range of housing types, predominantly terraced homes.
Across Kent and around South Darenth: fuel drain cover
South Darenth sits in the DA postcode area, and the vans that answer petrol in diesel call-outs there work the locations around it as well — St Margarets, Sutton at Hone and Horton Kirby among them. A forecourt, a supermarket car park, a lay-by or your own drive are all spots our engineers work, and your car doesn't need to come to us.
Still at the petrol pump in South Darenth?
Nothing beats it: that is where you now are. Keep it off. Call.