Launceston: Petrol in a Diesel Car? How Worried to Be
Unstarted? Then less anxious than you probably are. Everyone in Launceston starts with "have I ruined it?", and the honest answer is normally no: petrol left inside that tank of a diesel remains harmless till priming, cranking or driving pulls it into the system. To keep it that way, ring Petrol in Diesel and leave the motor switched off. Further down, you will find what petrol actually does inside a diesel, how far it may have gone, and how to stop it happening to you a second time.
The engine and petrol in a diesel: what happens
Passing through a motor, diesel is doing two things at the same time. Before it ignites, it lubricates — and then it burns. Very fine clearances go into the injectors and the high-pressure fuel pump, and only your diesel running through stops their surfaces grinding together.
Poorly at the first, not at all at the second: that is petrol. A pump running on a petrol blend is wearing itself out, because petrol is runnier than diesel and takes away the lubrication your fuel system relies on. Petrol is also made to resist igniting under compression — the reverse of what a diesel needs from its fuel — and that is where any knocking starts.
Put these together and the shape of the trouble is clear. The harm is done by movement, not by contact. Where the petrol is only inside your tank, it is a fault of fuel, nothing more. 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 that petrol is where a mechanical issue starts.
Petrol in a diesel around Launceston: how serious is it? Four situations
Fuelled up, never started. The best case there can be. At a forecourt, and truly only there, the petrol is still confined to your tank — because everywhere else the car was driven to reach it. The job is emptying and purging on the spot.
Started for a second, or just your ignition on. With the system primed, your lines and filter now contain petrol that has come from your tank. Normally little more than draining, cleaning and seeing to the filter, and so still straightforward.
Driven a couple of miles. Now your pump has spent these miles working on diluted fuel. How hard the vehicle was driven matters as much as how far, and the work covers that tank, the lines, your filter and clean fuel through the whole circuit. A school run to Windmill Hill Academy is one matter. Very different a second time: a trip to Plymouth, under 25 miles away, or some mileage on the M5, under 50 miles from Launceston, where the engine kept working hard.
Driven on until it protested — knocking, smoke, an uneven idle, a soft throttle. The motor is telling you the fuel is no longer behaving like diesel. Pull up on the spot — on the verge on Windmill Hill, at the kerb, down a side road — and don't move it again. What goes first is still the drain and flush-through, and that takes care of it, with lasting damage very unusual if a vehicle is stopped soon.
Stories Launceston drivers hear about petrol in a diesel
False: topping up to full with diesel makes it fine. It doesn't. A bigger tank of the same mix is all it gives, because topping up takes out nothing. The idea behind that advice — that diesel fuel systems tolerate petrol by percentage — is wrong.
Not so: a newer diesel copes with a bit of petrol. Rather, the reverse. A current diesel runs its fuel through smaller parts at higher pressure, which makes the lubrication matter more, not less.
The myth that catches motorists off guard: if it starts and drives, it must be unharmed. The motorist of a petrol motor fed diesel usually stops, since it will not run, and the harm stops with them. Whilst your pump grinds, a diesel fed petrol normally starts, idles and drives away as if nothing has happened. A running engine does not mean fine.
"A drop of two-stroke oil and drive it home" — a myth, borrowed from a fix from years ago, for a separate problem. None of what petrol weakened gets put back by it — and afterwards, your tank still contains that petrol.
The next start draws petrol back round your pump out of your lines and your filter, where some of that ends up once the motor has been run. That's why a DIY tank drain doesn't sort it — a myth. Draining petrol into a can by the kerbside is also truly dangerous.
How does petrol in a diesel take place?
On purpose? Never. Through carelessness? Seldom, if ever. A diesel nozzle generally will not go into a petrol vehicle, but the narrower petrol nozzle goes into the filler of a diesel almost without resistance — so forecourts make this one mistake straightforward, and just in that direction.
Routine and the vehicle getting out of step is how it occurs. Courtesy car, hire car, or a motor that is brand new. Households running one of each, petrol and diesel. A forecourt you know, but with its pumps laid out differently. Fuelling up in a rush on the way to Gunnislake, with a train to catch. Years of petrol cars behind you, a diesel Volkswagen Golf in front of you on the forecourt for its first tank — that's when. Add rain, a phone call or a back seat full of children, and the hand does what it has always done.
Launceston drivers: how to prevent petrol in a diesel next time
- Green 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.
- Plenty of cars state the fuel inside your filler flap or on the cap, so check it on your first fill in a vehicle you don't know.
- Good intentions count for less than a sticker or a fob in a bright colour on the diesel's key when a home has one of each. So label it.
- Before the nozzle comes off the pump the first time you fuel a hired or new motor, say "diesel" out loud. Daft, yes, but it works.
- Mistakes like this are easy to make while your mind is on something else, and so your phone goes away.
- Some diesels have a filler designed to reject a petrol nozzle, and devices you can add exist for motors without one. Such an inhibitor helps up to a point — as a backstop, not a reason to stop reading the petrol pump.
- Spotting it mid-fill? Stop at once. A thinner mixture results from less petrol inside your tank, yet the next stage remains the same: do not fire it up.
Already put petrol in a diesel around Launceston?
Then, there is just a short order of things. Leave it unstarted, with your ignition switched off as well. Yet on the forecourt, at the nearest petrol station or anywhere else? Ask the attendants to help you roll the car clear of the petrol pump. Then ring 0333 366 0103 and tell us what went in, about how much, and whether it has run.
If it was AdBlue instead of petrol, say so. That is a different issue — corrosion and deposits instead of lost protection — and it has its own page for Launceston.
What makes one Launceston petrol in a diesel job cost more than the next
There is no fair single price for this, because the four situations above are four different tasks. Chiefly, the cost shifts with which one you're in. After that it's the proportion — how much petrol went in against how much that tank holds — and then where the vehicle is and whether our van can reach it safely.
That's why our technicians ask three queries before pricing instead of after: what was put in, how much, and if it's run. Their replies are what change a range into one firm number.
About Launceston, briefly
Launceston is a town in Cornwall, situated on the banks of the River Kensey, with a mix of terraced housing and other buildings. Launceston sits at an elevation of around 135 metres, overlooking the surrounding countryside. Launceston is close to several nearby places, including Chapel, St Thomas, and Kensey Valley Meadow, and is approximately 20 miles from Plymouth. Launceston has a population of around 9626 people, making it a significant urban centre in the region.
Fuel drain cover across Cornwall, Launceston included
Petrol in diesel jobs around Launceston — part of the PL postcode area — go to teams that also cover the locations around it, Chapel, St Thomas and Kensey Valley Meadow included. A forecourt, a supermarket car park, a lay-by or your own driveway are all spots our technicians work, and the vehicle does not need to move to us.
At the petrol pump around Launceston, right now?
Then, you couldn't be in a better spot. Keep it off. Ring.