Scothern: Petrol in a Diesel Car? How Worried to Be
Less than you probably are, provided it hasn't been started. Until your ignition primes the pump, the starter cranks, or your vehicle is driven, petrol in a diesel tank simply waits there and does nothing. Which makes the honest reply to the first Scothern query — "have I ruined it?" — usually no. To keep it like that, call Petrol in Diesel then leave the motor switched off. The remainder of this page covers 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 a second time.
Petrol in a diesel: what does it do to the motor?
Diesel does two tasks on its way through a motor. It lubricates to begin with, and only then does it burn. Your high-pressure pump and the fuel injectors are built to extremely fine gaps, and your diesel passing through them is what keeps those surfaces from wearing down against one another.
Of those two jobs, petrol manages the first poorly and the second never. Being less viscous than diesel, petrol strips away the lubrication a fuel system needs, so a pump running on that mixture wearing itself. It's also made to resist igniting under compression — the reverse of what a diesel needs — which is where you get the rattling.
Seen together, they make clear the shape the issue takes. Contact doesn't do the damage — circulation does. All a tank with petrol in it amounts to is a fuel issue. Whatever a worn pump sheds goes on, borne by your fuel, into the injectors downstream, which is why a pump that has been working on the petrol is where a mechanical fault begins.
Scothern, petrol in a diesel: four situations, from mild to significant
Fuelled but never started — the best it gets. Just your tank has petrol in it, and so the task is emptying the tank and rinsing the system where your car stands. This situation can only truly take place on a forecourt: anywhere else, your car got there by being driven.
A brief spell of running, or just your ignition on. With the system primed, the fuel lines and filter already hold petrol that came from your tank. Drain, flush, deal with your filter: still normally straightforward.
The pump has worked a couple of miles on weakened fuel — that's what driving the vehicle meant. How hard the car was driven matters as much as how far, and the work covers that tank, the fuel lines, the filter and fresh fuel through the whole circuit. Driving the children to Ellison Boulters Church of England Primary School is one kind of trip. A run as far as Lincoln, under 10 miles away, is a very different job. So is any miles on the M180, under 25 miles from Scothern, where the motor has been running hard throughout.
It protested, and only then stopped: smoke, knocking, a throttle gone soft, an idle gone ragged. What you are hearing is the engine signalling fuel that no longer acts like diesel. Whether it is the verge on Craypool Lane, a lay-by or a side street, stop where you are and leave it. A car pulled over early very seldom has lasting damage, since the drain and the flush, which still come first, sort it out.
Myths Scothern people hear about petrol in a diesel
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 are left with a bigger tank, still the same mixture. Percentage is not how a diesel fuel system tolerates petrol, whatever that advice assumes.
Not so: a modern diesel copes with a bit of petrol. If anything, the opposite. At higher pressure, through more precise parts: that is how a newer diesel handles its fuel, so the lubrication matters for more, not less.
This is the one that catches drivers. Myth: "If it starts and drives, there is no damage done." Feed diesel to a petrol engine and it normally won't run, so the driver stops — and the damage stops with them. A diesel fed petrol generally starts, ticks over and drives away as if nothing has happened, whilst your pump grinds. Fine and running aren't the same thing.
Myth: "Add some two-stroke oil and drive the car home." It's an old workaround for a distinct issue. That petrol is still in your tank afterwards, and what it has weakened is not put back.
Myth: "Drain that tank yourself and you're sorted." Once the motor has run, some of the petrol is no longer in the tank: it's in the filter and the lines, and it goes straight back through your pump on your next start. It's also really hazardous to drain petrol into a can by the kerbside.
Petrol in a diesel: how does it happen?
Nobody does it on purpose, and it is seldom carelessness. The forecourt makes it easy: the petrol nozzle is the slimmer of the two, and it slips into a diesel filler with almost no resistance, whilst a diesel nozzle generally will not go into a petrol vehicle at all. So the slip runs one way.
Routine and the car falling out of step is when it happens. Courtesy car, hire car, or a vehicle that's new. One petrol and one diesel on the drive of the same household. A forecourt you know, but with its pumps laid out differently. Filling up in a hurry en route to Lincoln Central, with a train to catch. Years of petrol vehicles behind you, a diesel Volkswagen Golf in front of you on the forecourt for its first tank — that's when. Throw in a back seat full of kids, a phone call or rain, and the hand wins.
How to avoid petrol in a diesel on your next fill-up in Scothern
- Not every forecourt in the UK follows green for unleaded and black for diesel, even if most usually do. Read the petrol pump's label; the colour is just a clue.
- The first fill in a strange vehicle is the time to check your filler flap — inside it, or on the cap, many vehicles state the 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 home with one of each.
- "Diesel", aloud, before you pick up the nozzle — each time a new or hired car gets its first tank. It seems daft. It does the trick.
- Tuck your phone away. This is an easy mistake to make whilst you're thinking about something else.
- Add-on devices are available for motors without one, and some diesels come with a filler that won't accept a petrol nozzle. Helpful — but a safety net only, never a reason to stop checking the label.
- Spotting it halfway? Stop there and then. A weaker blend results from less petrol in the tank, but the next step remains the same: don't start the vehicle.
Put petrol in a diesel in Scothern already?
Short and simple, then, is the order of things. Never start the vehicle, and don't switch your ignition on. The attendants at the forecourt — whether at UK itself or wherever you filled up — will normally help push it clear of the pump if you ask. Then call 0333 366 0103 and tell us what went in, about how much, and if it's run.
AdBlue, not petrol? Then tell us. Corrosion and deposits, not lost protection, make it a separate issue — Scothern has a page just for it.
What makes one Scothern petrol in a diesel job cost more than the next
The four scenarios above are four different tasks, so no single price for this would be fair. Which of them you are in is chiefly what moves the cost. Where the vehicle is matters too, and whether a van can safely get to it, after the ratio of petrol to what the tank takes.
Before any quote, not after, come three questions: your fuel that was put in, its volume, and whether it's run. That's why. Given the answers, there is a straight figure rather than a range.
About Scothern and where it is
Scothern is a small village in Lincolnshire, situated near the River Witham and close to the city of Lincoln. Scothern has a low elevation of around 15 metres, and its riverside setting provides a distinctive character to the village. Scothern is home to approximately 975 residents, who mostly live in detached houses, and is located near other local places such as Sudbrooke and Dunholme.
Fuel drain cover around Scothern and across Lincolnshire
Sudbrooke, Sudbrooke Park and Dunholme are among the locations near Scothern that the same teams work, answering petrol in diesel call-outs across Scothern's LN postcode area. You need not bring the car to us. Forecourts, supermarket car parks, lay-bys and your own drive are all locations we drain.
Scothern: still at the petrol pump?
In that case, you couldn't be in a better place. Keep it off. Phone.