Wem: Petrol in a Diesel Car? How Worried to Be
Less than you probably are, if it has not been started. Till the ignition primes the pump, your starter turns, or your vehicle is driven, petrol in a diesel tank simply waits there and does nothing. Which makes the honest reply to the first Wem question — "have I wrecked it?" — usually no. Leave your engine off and call Petrol in Diesel — that keeps it that way. The rest of this page explains what petrol actually does to a diesel, how to judge how far it has got, and how to make sure it doesn't happen to you again.
What petrol in a diesel does to your engine
On its way through a motor, diesel has two jobs. It ignites, and before it burns it protects. Extremely fine tolerances are built into the injectors and the high-pressure fuel pump, and only your diesel running through keeps their surfaces from grinding together.
The second task petrol does not do at all, and the first it does badly. A pump working on a petrol mixture is wearing itself out, since petrol is thinner than diesel and takes away the protection your fuel system depends on. Petrol is also made to resist igniting under compression — the reverse of what a diesel needs from its fuel — and that's where any clattering comes.
Combined, those make the shape of the trouble plain. Not contact but movement is what does the harm. Where that petrol is only inside the tank, it is an issue of fuel, nothing more. Whatever a worn pump sheds travels on, carried by your fuel, into the fuel injectors further along, which is why a pump that has worked on the petrol is where a mechanical issue begins.
Four scenarios our technicians see in Wem: how serious is petrol in a diesel?
Filled up, and never started: nothing beats it. The petrol is in your tank and just the tank, and the task is a drain and a flush where the vehicle stands. This is the one scenario that can only truly occur on a forecourt, as anywhere else the car has been driven to get there.
Your ignition switched on, or a short start. Petrol has left that tank and got to your filter and your lines, because your system has been bled. Still usually simple: drain, flush, and the fuel filter sorted.
Those few miles driven were the pump labouring on fuel diluted by petrol the whole way. Mileage is only half of that; how hard it was driven matters equally. Either way the work includes the tank, the lines, the filter and fresh fuel through the whole system. On the school run to St Peter's CofE Primary School, the distance is short. Very different once more: a run to Wrexham, under 25 miles away, or any mileage on the M54, under 15 miles from Wem, where your engine kept working hard.
Driven on until it complained — knocking, smoke, an uneven idle, a soft throttle. What you are hearing is the engine signalling fuel that no longer runs like diesel. Pull up wherever you are — the verge on Leek Street, a lay-by, a side street — and leave the car where it is. What goes first is still the fuel drain and flush, and that sorts it out, with permanent damage very rare when a car is stopped quickly.
Petrol in a diesel stories Wem people hear
It will not be fine. The myth: "Fill it the rest of the way with diesel and it'll be." Nothing is removed by topping up — you're left with a fuller tank, still the same mix. Percentage isn't how a diesel fuel system tolerates petrol, whatever that guidance assumes.
If anything, the reverse is true. Myth: "A current diesel can cope with a bit of petrol." At higher pressure, through smaller parts: that's how a modern diesel handles its fuel, and so the lubrication counts for more, not less.
"It starts, it drives, and so there is no harm" — the myth that catches most drivers than any other. The driver of a petrol motor fed diesel normally has no choice but to stop, since it will not run, and the damage stops there. While the pump grinds, a diesel fed petrol normally starts, ticks over and drives away as if nothing has happened. Fine and running are not the same at all.
An old workaround for a separate problem is behind this one. Myth: "Add some two-stroke oil and drive the vehicle home." None of what petrol weakened gets put back by it — and later, the tank still holds that petrol.
"Drain it yourself and you're sorted" — a myth, since after it has been running some petrol sits in your filter and lines, waiting to go straight back through the pump on your next start. It is also genuinely hazardous to drain petrol into a can at the roadside.
How does petrol in a diesel take place?
On purpose? Never. Through carelessness? Rarely, if ever. The petrol nozzle is the slimmer of the two and slips into a diesel filler with almost no resistance; a diesel nozzle mostly will not go into a petrol car at all. The forecourt makes it easy, and the slip runs one way.
When routine and the vehicle stop matching, it happens. A new motor, a hire car or a courtesy car. A household with one petrol and one diesel on the driveway. A forecourt you know, only with its pumps arranged differently. Rushing for a train at the nearest station and filling up en route. Years of petrol motors behind you, a diesel Renault Megane in front of you on the forecourt for its first tank — that's when. Your hand repeats what it has always done once you add rain, a phone call or a back seat full of kids.
Next time you fill up in Wem: preventing petrol in a diesel
- A green handle for unleaded and black for diesel is usual in the UK — but not on every forecourt. Go by the label on the petrol pump, not the colour.
- In a vehicle you don't know, look inside the flap over your filler or at the cap before the first fill: many vehicles print the fuel type there.
- Good intentions do less than a sticker or a fob in a bright colour on your diesel's key if a home has one of each. So label it.
- "Diesel", aloud, before you pick up the nozzle — every time a new or hired car needs its first tank. It sounds daft. It works.
- Tuck the phone away. This is an easy mistake to make while you are thinking about something else.
- Some diesels come with a filler designed to reject a petrol nozzle, and devices you can add exist for vehicles without one. Such an inhibitor helps up to a point — as a backstop, not a reason to stop reading the pump.
- The moment you realise, stop: less petrol in your tank makes a weaker blend. What to do next does not change, though — still do not crank it.
Wem: already put petrol in a diesel?
Short and simple, then, is the order of things. Leave it unstarted, with your ignition off as well. If you're still at the forecourt — Valero or anywhere else — ask the staff to help you push it clear of the pump. Phone 0333 366 0103 next, with three answers — your fuel, the rough quantity, and if it has run.
AdBlue, not petrol? Then say so. Corrosion and deposits, not lost lubrication, make it a separate fault — Wem has a page just for it.
One petrol in a diesel job in Wem costs more than another. Why?
An honest single quote does not exist here: four situations, four separate tasks. What moves your cost is mostly which of them you're in. Beyond that it is the ratio — how much petrol got in against how much your tank takes — and then where the car is and whether a van can reach it safely.
Before any quote, not after, we ask three queries: your fuel that was put in, the quantity, and whether it has run. That is why. A range turns into a straight figure once those replies are in.
About Wem
Wem is a small town in Shropshire, situated on the banks of the River Roden at an elevation of around 83 metres. Wem lies near the villages of Tilley, Tilley Green, and Barkers Green, and is approximately 17 miles from Wrexham. Wem has a population of around 6659 people, predominantly living in detached houses. Wem is located in the West Midlands region, about 144 miles northwest of London.
Fuel drain cover around Wem and across Shropshire
Petrol in diesel calls in Wem — part of the SY postcode area — go to teams that likewise cover the locations around it, Tilley, Tilley Green and Barkers Green among them. No need to move the car to us. Forecourts, supermarket car parks, lay-bys and your own drive are all places we drain.
Still at the pump in Wem?
In that case, you could not be in a better position. Keep it off. Ring.