Four Marks: Petrol in a Diesel Car? How Worried to Be
Not started? Then less worried than you probably are. Till the ignition primes your pump, your starter cranks, or your car is driven, petrol in a diesel tank simply sits there and does no harm. Which means the truthful reply to that first Four Marks query — "have I ruined it?" — normally no. Leave your motor off then phone Petrol in Diesel — that keeps it like that. Keep reading for three things: the effect petrol has inside a diesel motor, the clues of how far it has got, and ways to make sure you don't do it again.
The engine and petrol in a diesel: what goes on
Two jobs fall to diesel on its journey through a motor. It protects first, and only then does it burn. Made to very fine clearances, the fuel injectors and the pump depend on your diesel moving through them to stop their surfaces wearing against one another.
Of these two tasks, petrol manages the first badly and the second never. The clattering comes from petrol being made not to ignite when compressed, which is exactly the opposite of what a diesel needs. On top of that it is thinner than diesel, it strips out the protection the system depends on, and any pump working on that blend is wearing itself.
Seen together, they make clear what shape the trouble has. The harm is done by movement, not by contact. Any tank with petrol in it is a fuel issue. Whatever a worn pump sheds goes on, carried by your fuel, into the injectors further along, which is why a pump that has worked on that petrol is where a mechanical issue begins.
Petrol in a diesel around Four Marks: how serious is it? Four cases
Fuelled but not once started — as good as it gets. On a forecourt, and genuinely only there, that petrol is still confined to that tank — because anywhere else your car was driven to reach it. The task is emptying and cleaning on the spot.
Started for a moment, or only the ignition on. With the system primed, your lines and filter now hold petrol that came from the tank. That's usually still an easy task — a drain, a flush, and the filter dealt with.
Driven a few miles. Now your pump has spent these miles working on diluted fuel. Tank, lines, filter, then fresh fuel run through the whole circuit: that is the work, and the way your car was driven matters as much as the mileage. A school run to Four Marks Church of England Primary School is one matter. Very different a second time: a trip to Winchester, under 15 miles away, or any miles on the M3, under 10 miles from Four Marks, where your engine never stopped labouring hard.
Driven on until it complained — clattering, smoke, a ragged idle, a soft throttle. What you are hearing is the motor reporting fuel that no longer acts like diesel. Pull up wherever you are — the verge on Station Approach, a lay-by, a side street — then leave it where it is. What goes first is still the fuel drain and flush, and that deals with it, with permanent damage very rare when a car is pulled over early.
Petrol in a diesel stories Four Marks motorists hear
False: topping up to full with diesel makes it fine. It does not. Topping up removes nothing; it gives you a fuller tank of the same mix. The idea behind the guidance — that diesel fuel systems tolerate petrol by percentage — is wrong.
Myth: a current diesel copes with a bit of petrol. Rather, the opposite. More precise parts and higher pressure are how a current diesel runs its fuel, and that makes the lubrication count more, not less.
This is the one that catches people. Myth: "If it starts and drives, there's no damage done." Feed diesel to a petrol motor and it usually will not run, and so the motorist stops — and the damage stops with them. A diesel fed petrol normally starts, ticks over and drives away as if nothing has happened, whilst the pump wears. 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 distinct issue. What petrol has weakened stays thinned, and the petrol stays in the tank anyway.
"Drain it yourself and you're sorted" — a myth, because after it has been running some petrol lies in the filter and lines, ready to go right back through the pump at your next start. It is also genuinely risky to drain petrol into a can by the roadside.
How does petrol in a diesel occur?
It is seldom carelessness, and no one does it on purpose. One way only, since of the nozzles: the smaller petrol one slides inside a diesel filler with almost no resistance, whereas the diesel one generally will not fit a petrol car. That's how the forecourt makes it straightforward.
When routine and the car stop matching, it happens. Hire cars, courtesy cars, and cars that are new to you. One petrol and one diesel on the drive of the same household. The pumps in a different order on a well-known forecourt. A rushed fill en route to Alton with a train to catch. The first fill-up in a diesel Renault Megane after years of driving petrol is exactly the moment it occurs. Add rain, a phone call or a back seat full of children, and the hand does what it has always done.
Four Marks people: how to avoid petrol in a diesel next time
- A green handle for unleaded and black for diesel is normal in the UK — but not on every forecourt. Go by the label on the pump, not the colour.
- The first fill in an unfamiliar car is the time to check your filler flap — inside it, or on the cap, many cars state which fuel they take.
- A coloured fob or a sticker on your diesel's key achieves more than any amount of meaning to remember, for a house with one of each.
- It seems daft and it works: on the first fill in a new or hired car, say "diesel" aloud before you take the nozzle off the petrol pump.
- Thinking about something else is when this becomes an easy mistake to make, so tuck your phone away then keep your mind on the pump.
- Up to a point, a misfuel inhibitor helps: some diesels have a filler designed to reject a petrol nozzle, and aftermarket devices are available for the rest. Treat it as a safety net, then keep checking the pump.
- Stop the moment you notice. Less petrol inside the tank makes a thinner blend. It does not change what to do next, which is still not to fire it up.
Petrol already in a diesel around Four Marks? Start here
Then the order of things is brief. Starting it is out, and so is turning on the ignition. If you're still at the forecourt — BP or anywhere else — ask the attendants to help you roll it away from the petrol pump. Then phone 0333 366 0103 and tell us what got in, about how much, and if it's run.
Say so if it was AdBlue rather than petrol: it is a different fault, with its own page for Four Marks, since AdBlue brings corrosion and deposits instead of lost protection.
One petrol in a diesel task in Four Marks costs more than another. Why?
Four different tasks lie behind the four situations above — which is why there is no fair single price. Chiefly, your cost moves with which situation you're in. Where the car is matters too, and whether our van can safely reach it, after the ratio of petrol to what your tank holds.
That is why we ask three questions before quoting instead of after: what went in, how much, and whether it's run. Their replies are what turn a range into one firm number.
About Four Marks
Four Marks is a locality in Hampshire, situated inland at an elevation of 207 metres, approximately 12 miles from Winchester and 48 miles from London. Four Marks is characterized by its predominantly detached housing stock, reflecting its development as a residential area. Four Marks sits near other small places such as Hawthorn, South Town, and Soldridge, and has a population of around 1590 residents.
Fuel drain cover in Four Marks and across Hampshire
Four Marks rests in the GU postcode area, and the teams that answer petrol in diesel calls there work the spots near it as well — Hawthorn, South Town and Soldridge among them. A forecourt, a supermarket car park, a lay-by or your own drive are all places our technicians drain, and the car does not need to come to us.
Four Marks: still at the petrol pump?
In that case, you could not be in a better position. Leave the car turned off, then ring.