Smoky Hole: Petrol in a Diesel Car? How Worried to Be
Unstarted? Then less anxious than you likely feel. Petrol sitting in a diesel tank does nothing to the engine until something draws it through your fuel system — your ignition priming the pump, the starter, or driving on its own. So the fair answer to the first question anyone in Smoky Hole asks, "have I ruined it?", is generally no. Keep it that way: leave the motor off and ring Petrol in Diesel. Below, you will find what petrol actually does inside a diesel, how far it may have got, and how to stop it happening to you again.
The engine and petrol in a diesel: what goes on
Diesel has two jobs on its way through an engine. Oiling comes before burning; it does both. Extremely fine tolerances are built into the fuel injectors and your high-pressure pump, and just the diesel running through stops those surfaces grinding together.
Of those two tasks, petrol handles the first badly and the second never. A pump working on a petrol mixture is wearing itself out, because petrol is thinner than diesel and takes away the protection the fuel system depends on. Petrol is also made to resist igniting under compression — the reverse of what a diesel wants from its fuel — and that's where any clattering starts.
Taken together, they make clear the shape the issue takes. The harm is done by movement, not by contact. Any tank with petrol in it is a fuel problem. The start of a mechanical one is a pump that has been working on that petrol — and whatever a worn pump sheds moves on with the fuel to your injectors downstream.
Smoky Hole, petrol in a diesel: four cases, from mild to serious
Fuelled but never started — the best it gets. Being at a forecourt is what makes this possible: elsewhere, the vehicle has been driven there to begin with. With that petrol held inside that tank alone, it's emptied and cleaned right where it stands, and nothing more is needed.
Started for a moment, or only your ignition on. Petrol has left your tank and reached the filter and the lines, because the fuel system has been bled. Normally nothing more than clearing, flushing and seeing to the filter, and so still straightforward.
The pump now worked a few miles on diluted fuel — that's what driving it does. Mileage is only half of it; how hard it was driven matters just as much. Either way the work includes the tank, your lines, the filter and fresh fuel through the entire circuit. Driving the kids to Peaslake Free School is one kind of trip. Very different again: a trip to Westminster, under 50 miles away, or any distance on the M25, under 10 miles from Smoky Hole, where the motor never stopped running hard.
Clattering, an uneven idle, smoke, a throttle gone soft: driven until it complained. The fuel isn't behaving like diesel any more, and the motor is saying so. Stop wherever you are — the verge on Burchets Hollow, a lay-by, a side street — then leave the vehicle where it is. The drain and flush still go first, and they take care of it: when a vehicle is pulled over early, long-term damage is very uncommon.
Myths Smoky Hole people hear about petrol in a diesel
False: topping up to full with diesel makes it fine. It does not. Nothing is removed by topping up — you are left with a bigger tank, still the same mixture. The idea behind that advice — that diesel fuel systems tolerate petrol by percentage — is wrong.
If anything, the reverse is true. Myth: "A modern diesel can cope with a bit of petrol." More precise components and higher pressure are how a current diesel runs its fuel, and that makes the protection matter more, not less.
This is the one that fools motorists. Myth: "If it starts and drives, there is no damage done." Feed diesel to a petrol motor and it normally won't run, so the driver stops — and the harm stops with them. Feed petrol to a diesel and it normally fires up, idles and drives away like nothing has happened — all the while its pump is wearing. Being able to run is not the same as being fine.
Not so: a two-stroke additive lets you to drive home. It is an old workaround, supposed for another problem. What petrol has diluted stays thinned, and that petrol stays inside that tank regardless.
"Drain it yourself and you are sorted" — a myth, since after it has been running some petrol sits in your filter and lines, ready to go right back through the pump on the next start. It is also genuinely hazardous to drain petrol into a can at the kerbside.
How it happens: petrol in a diesel
On purpose? Never. Through carelessness? Rarely, if ever. The forecourt makes it simple: the petrol nozzle is the narrower of the two, and it slides into a diesel filler with almost no resistance, while a diesel nozzle generally will not go into a petrol vehicle at all. So the mistake runs one way.
When routine and your car stop matching, it occurs. A vehicle that's new to you — hired, on loan as a courtesy car, or just bought. One petrol and one diesel on the drive of the same household. A familiar forecourt with the pumps in a different order. A train to catch, and a rushed fill en route to Gomshall. A new-to-you diesel Volkswagen Golf, its first fuelling, and a driver used to petrol: precisely when it occurs. Add a back seat full of kids, a phone call or rain, and habit takes over.
Smoky Hole motorists: how to avoid petrol in a diesel next time
- 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 only a clue.
- Check your filler flap. Plenty of vehicles state the fuel inside the flap or on the cap. Look at it on your first fill in a vehicle you do not know.
- One of each in the household? Mark your key to the diesel — a bright fob, a sticker — since intending to remember isn't enough.
- Before the nozzle leaves the petrol pump the first time you fill a hired or new car, say "diesel" out loud. Silly, yes, but it does the trick.
- Put the phone away. This is an easy mistake to make whilst you're thinking about something else.
- A misfuel inhibitor helps, up to a point. Some diesels come with a filler built to reject a petrol nozzle, and add-on devices exist for cars without one. They are a safety net, not a reason to stop reading the petrol pump.
- Noticing it mid-fill? Stop there and then. A thinner blend results from less petrol inside that tank, yet the next stage remains the same: don't fire it up.
Put petrol in a diesel in Smoky Hole already?
Then the order of things is brief. Do not start it, and don't turn your ignition on. Yet at the forecourt, at Esso or anywhere else? Ask the staff to help you roll it clear of the petrol pump. What was put in, about how much, and if it has run: tell us those when you call 0333 366 0103.
If it was AdBlue rather than petrol, say so. That is a separate issue — corrosion and deposits instead of lost protection — and it has its own page for Smoky Hole.
Smoky Hole petrol in a diesel tasks: why one costs more than another
A fair single price does not exist here: four situations, four separate tasks. The situation itself does most of the work of moving the cost. Where the car is counts too, and whether our van can safely get to it, after the share of petrol to what that tank takes.
Three queries come first, before quoting, rather than after — what was put in, how much, has it run — and that is the reason. The replies turn a range into a straight figure.
About Smoky Hole itself
Smoky Hole is a small suburban area in Surrey, situated on the riverside with an elevation of around 129 metres. Smoky Hole lies approximately 25 miles south-west of central London, near the villages of Peaslake and Sutton Abinger. Smoky Hole is characterized by its predominantly detached housing stock, reflecting the area's residential nature. Smoky Hole remains a relatively quiet and secluded community, despite its proximity to the capital.
Across Surrey and in Smoky Hole: fuel drain cover
Petrol in diesel jobs in Smoky Hole — part of the GU postcode area — go to vans that likewise cover the spots around it, Peaslake, Hoe and Sutton Abinger among them. The car doesn't need to move to us: we drain on a forecourt, in a supermarket car park, in a lay-by or on your own driveway.
In Smoky Hole and still at the petrol pump?
The best position there is, then — that's where you are. Leave the vehicle switched off, and ring.