Greylees: Petrol in a Diesel Car? How Worried to Be
Far less than you likely are, if it has not been started. Till the ignition primes your pump, the starter turns, or your car is driven, petrol in a diesel tank just waits there and does no harm. Which makes the truthful reply to the first Greylees question — "have I wrecked it?" — normally no. Leave your motor off then phone Petrol in Diesel — that keeps it that way. What petrol actually does to a diesel, how to judge how far it has travelled, and how to stop it from happening again: that is the remainder of this page.
Inside your engine: what petrol in a diesel really does
On its way through an engine, diesel does two jobs. Oiling comes before burning; it does both. Extremely fine tolerances go into your injectors and your high-pressure pump, and just your diesel running through stops those surfaces grinding together.
The second job petrol does not do at all, and the first it does poorly. Being less viscous than diesel, petrol strips out the protection a fuel system needs, so a pump on the mixture wearing itself. It is equally made to resist igniting under compression — the reverse of what a diesel needs — which is where you get the knocking.
The shape of the trouble is plain once you put those together. It is circulation that causes the damage, not contact. A tank with petrol in it is a fuel fault. Whatever a worn pump sheds goes on, borne by your fuel, into the fuel injectors further along, which is why a pump that has worked on that petrol is where a mechanical issue starts.
How serious is petrol in a diesel? Four scenarios our technicians see in Greylees
The best case there can be: filled up, never started. On a forecourt, and really only there, the petrol is still limited to that tank — since anywhere else the car was driven to reach it. The job is draining and cleaning on the spot.
The ignition switched on, or a short start. Petrol has come out of the tank and reached the filter and your lines, because your system has been primed. Still usually straightforward: drain, flush, and the fuel filter seen to.
Your pump now worked a couple of miles on weakened fuel — that is what driving the car does. Tank, lines, filter, then clean fuel put through the entire system: that's this work, and the way your car was driven counts as much as the miles. Short trips, such as the school run to St Botolph's C of E Primary School, are one matter. A run as far as Lincoln, under 25 miles away, is a very different task. So is any mileage on the Great North Road, under 50 miles from Greylees, where the engine has been labouring hard throughout.
Knocking, a ragged idle, smoke, a throttle gone soft: driven till it complained. The motor is telling you your fuel is no longer acting like diesel. Whether it's the verge on Willoughby Road, a lay-by or a side street, stop there then leave it. What goes first is still the fuel drain and flush-through, and that sorts it out, with permanent damage very unusual when a vehicle is pulled over soon.
Petrol in a diesel myths Greylees drivers hear
Myth: "Fill it the rest of the way with diesel and it will be fine." It will not. Topping up removes nothing; it gives you a fuller tank of the same mixture. The assumption behind that guidance — that diesel fuel systems accept petrol by percentage — is wrong.
Not so: a newer diesel copes with a bit of petrol. If anything, the opposite. A modern diesel runs its fuel through smaller components at higher pressure, which makes the lubrication count more, not less.
This is the one that catches drivers. Myth: "If it starts and drives, there's no damage done." Diesel in a petrol motor normally leaves a motor that will not run: the motorist stops, and so does the damage. Whilst your pump grinds, a diesel fed petrol usually starts, ticks over and drives away as if nothing has happened. Running isn't the same as fine.
Myth: a two-stroke additive lets you to drive home. It was an old fix, supposed for another problem. None of what petrol diluted is put back by it — and afterwards, that tank still contains the petrol.
"Drain it yourself and you are sorted" — a myth, because after it's been running some petrol lies in your filter and lines, waiting to go straight back through your pump on your next start. It is also truly dangerous to drain petrol into a can by the kerbside.
Why petrol in a diesel happens at all
Carelessness is rarely the cause, and no one means to do it. The forecourt makes it simple: the petrol nozzle is the slimmer of the two, and it slides into a diesel filler with almost no resistance, whilst a diesel nozzle mostly will not go into a petrol motor at all. So the error runs one way.
When routine and your car stop matching, it takes place. Hire cars, courtesy cars, and motors that are new to you. One petrol and one diesel on the driveway of the same household. The pumps in a different order on a well-known forecourt. Rushing for a train at Rauceby and filling up en route. Precisely the moment it happens: after years of driving petrol, someone fills a diesel Volkswagen Golf for the first time. With rain, a call arriving, or a car full of children to deal with, your hand simply does what it has always done.
Avoiding petrol in a diesel next time you fill up in Greylees
- Green for unleaded and black for diesel is normal in the UK — yet not on every forecourt. Trust the label on the pump, not the colour.
- Check the filler flap. Plenty of motors state the fuel type inside the flap or on the cap. Look at it on your first fill in any motor you don't know.
- Label your key. In a house with one of each, a coloured fob or a sticker on the diesel's key does more than any amount of meaning to remember.
- It sounds daft and it works: on the first fill in a new or hired car, say "diesel" out loud before you lift the nozzle off the petrol pump.
- Tuck the phone away. This is an easy mistake to make while you are thinking about something else.
- A misfuel inhibitor helps, up to a point. Some diesels have a filler built to block a petrol nozzle, and add-on devices are available for vehicles without one. They are a backstop, not a reason to stop reading the pump.
- Less petrol means a weaker blend, so stop the moment you notice — though remembering that your next stage is unchanged. It's still not to fire it up.
Already put petrol in a diesel in Greylees?
Then the order of things is short. Do not turn the ignition on, and don't fire it up. Ask the attendants to help you roll it clear of the pump if you are still on the forecourt, whether that is Murco or somewhere else. Next, 0333 366 0103. We will ask what went in, about how much, and if it has been run.
AdBlue, not petrol? Then say so. Corrosion and deposits, not lost protection, make it a separate problem — Greylees has a page all for it.
What makes one Greylees petrol in a diesel job cost more than the next
There is no honest single price for this, because the four situations above are four separate jobs. What moves your cost is chiefly which of them you're in. Two things come after that: the petrol that got in as a proportion of what the tank takes, then the place the car is in and whether our van can reach it safely.
What got in, how much, and whether it has run — three queries our technicians ask before quoting, not after, for exactly that reason. With the replies, there is a straight figure instead of a range.
About Greylees and where it is
Greylees is a village in Lincolnshire, situated on the riverside at an elevation of 27 metres, with detached housing being the predominant type of accommodation. Greylees lies near the villages of South Rauceby, New Quarrington, and Quarrington, and is approximately 17.8 miles from the city of Lincoln. Greylees has a population of around 847 people, and its location near the river gives it a unique character. Greylees is also relatively close to major cities, being around 102.8 miles from London.
Greylees and Lincolnshire: where our fuel drain cover runs
South Rauceby, New Quarrington and Quarrington are among the places near Greylees that the same vans work, answering petrol in diesel jobs across Greylees's NG postcode area. The vehicle does not need to move to us: our technicians drain at a forecourt, in a supermarket car park, in a lay-by or on your own drive.
At the pump around Greylees, still?
Then you're in the best spot there can be. Ring, and leave it turned off.