Boxted Cross: Petrol in a Diesel Car? How Worried to Be
Probably less than you already are — provided no one has started it. Till your ignition primes the pump, your starter turns, or the car is driven, petrol in a diesel tank simply waits there and does no harm. Which means the honest reply to that first Boxted Cross question — "have I ruined it?" — usually no. Leave the motor off then call Petrol in Diesel — that keeps it that way. The remainder of this page sets out 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.
What petrol in a diesel does to your engine
Two jobs fall to diesel on its journey through a motor. Before it burns, it lubricates — then it ignites. Very fine gaps go into your injectors and your high-pressure pump, and just your diesel flowing through stops their surfaces grinding together.
Badly at the first, not at all at the second: that is petrol. It is thinner than diesel and strips away the protection your fuel system rests on, and so a pump running on a petrol mixture is a pump wearing itself. And petrol is designed to resist igniting under compression, which is the opposite of what a diesel needs from its fuel. That's where the clattering comes from.
Combined, those make the shape of the problem clear. It's movement that causes the damage, not contact. Petrol in the tank is a fuel fault. A pump that has been running on that petrol is the start of a mechanical one, and whatever a worn pump sheds moves on with the fuel to the injectors further on.
Four scenarios we see around Boxted Cross: how bad is petrol in a diesel?
Fuelled, and not started: nothing beats it. On a forecourt, and really only there, the petrol is still limited to the tank — because everywhere else the vehicle was driven to get to it. The task is draining and flushing on the spot.
Ignition on, or started for a second. With the fuel system primed, your lines and filter now hold petrol that has come from the tank. That's generally still a simple task — a drain, a flush, and the filter dealt with.
Driven a few miles. Now your pump has spent those miles running on diluted fuel. How hard the car was driven counts as much as how far, and the work takes in your tank, the fuel lines, your filter and fresh fuel through the entire circuit. Driving the children to Boxted St Peter's Church of England School is one kind of trip. Any miles on the M11, under 50 miles from Boxted Cross, means the engine working hard throughout, and a run to Colchester, under 5 miles away, is a very different task as well.
It complained, and only then stopped: smoke, clattering, a throttle gone soft, an idle gone ragged. The engine is telling you the fuel is no longer acting like diesel. Leave it where it stops: a lay-by, a side street, the verge on Boxted Straight Road. What comes first is still the drain and flush-through, and that sorts it out, with permanent damage very uncommon when a vehicle is pulled over early.
What Boxted Cross motorists get told about petrol in a diesel — and the stories in it
"Top it up the rest of the way with diesel and it'll be fine" — a myth. It will not. A fuller tank of the same mixture is all you get, since topping up takes out nothing. The idea behind the advice — that diesel fuel systems accept petrol by percentage — is wrong.
Myth: "A modern diesel can cope with a bit of petrol." If anything, the opposite. At higher pressure, through more precise parts: that is how a current diesel handles its fuel, so the lubrication matters more, not less.
This is the one that fools drivers. Myth: "If it starts and drives, there's no harm done." The driver of a petrol motor fed diesel usually has no choice but to stop, because it will not run, and the damage stops there. While your pump wears, a diesel fed petrol normally starts, ticks over and drives away as if nothing has happened. Being able to run is not proof of being fine.
Myth: "Add some two-stroke oil and drive the car home." It's an old fix for a different fault. None of what petrol diluted is put back by it — and afterwards, the tank still contains the petrol.
"Drain it yourself and you are sorted" — a myth, since after it has been running some petrol sits in the fuel filter and lines, ready to go straight back through the pump at the next start. Besides, petrol cleared into a can by the road is genuinely risky.
How does petrol in a diesel happen?
On purpose? Never. Through carelessness? Rarely, if ever. A diesel nozzle mostly will not fit a petrol vehicle, yet the narrower petrol nozzle goes into the filler of a diesel nearly without resistance — so forecourts make this one mistake easy, and just in one direction.
Habit and the car getting out of step is when it takes place. Courtesy car, hire car, or a vehicle that's new. Households running one of each, petrol and diesel. The pumps in a different order on a well-known forecourt. A train to catch, and a rushed fill on the way to Colchester. Years of petrol cars behind you, a diesel Volkswagen Golf in front of you on the forecourt for its first tank — that's when. Throw in rain, a phone call or a back seat full of children, and the hand does what it has always done.
Boxted Cross drivers: how to avoid petrol in a diesel next time
- Green for unleaded and black for diesel is normal in the UK — yet not on every forecourt. Go by the label on the pump, not the colour.
- In a car you don't know, look inside the flap over the filler or at the cap before your first fill: plenty of motors print the fuel type there.
- Good intentions do less than a sticker or a fob in a bright colour on the diesel's key when a household has one of each. So mark it.
- Before the nozzle leaves the pump the first time you fill a hired or new vehicle, say "diesel" aloud. Silly, yes, but it does the trick.
- Put the phone away. This is an easy mistake to make while you're thinking about something else.
- A misfuel inhibitor helps, up to a point. Some diesels come with a filler designed to reject a petrol nozzle, and add-on devices exist for vehicles without one. They are a backstop, not a reason to stop checking the petrol pump.
- Less petrol makes a weaker mix, and so stop as soon as you notice — while remembering that your next stage is unchanged. It is still not to start it.
Already put petrol in a diesel in Boxted Cross?
The order of things is brief, then. Do not crank it, and don't turn the ignition on. Ask the staff to help you roll it clear of the pump if you are still at the forecourt, whether that's Shell or somewhere else. What was put in, about how much, and if it's run: tell us that when you ring 0333 366 0103.
AdBlue, not petrol? Then say so. Corrosion and deposits, not lost protection, make it a separate issue — Boxted Cross has a page just for it.
One petrol in a diesel job around Boxted Cross costs more than another. Why?
Four separate tasks lie behind the four situations above — which is why there's no fair single price. Which of them you're in is chiefly what moves your cost. Beyond that it is the ratio — how much petrol went in against how much the tank takes — and after that where the vehicle is and whether a van can reach it safely.
Ahead of any quote, not after, we ask three queries: your fuel that was put in, its amount, and if it has run. That's why. A range turns into a straight figure once the replies are in.
About Boxted Cross, for a moment
Boxted Cross is a village in Essex, situated near the River Colne and close to the nearby villages of Boxted and Langham Moor. Boxted Cross sits at an elevation of 47 metres, with detached housing being the predominant type of accommodation in the area. Boxted Cross is located near Colchester, which is approximately 4.5 miles away, and is around 54.4 miles from London.
Across Essex and in Boxted Cross: fuel drain cover
Boxted Cross sits in the CO postcode area, and the teams that answer petrol in diesel call-outs there work the locations near it as well — Boxted, Workhouse Hill and Langham Moor among them. You need not move the vehicle to us. Forecourts, supermarket car parks, lay-bys and your own drive are all places where we work.
In Boxted Cross and still at the pump?
Then you're in the best position there is. Switched off it remains; then ring.