Should You Worry? Petrol in a Diesel Car in Slyne
Less than you probably are, if it has not been started. Until your ignition primes the pump, your starter cranks, or your car is driven, petrol in a diesel tank just sits there and does no harm. Which makes the truthful reply to that first Slyne query — "have I wrecked it?" — normally no. Petrol in Diesel is who to call, with the engine kept off, so it remains that way. What petrol actually does to a diesel, how to gauge how far it has travelled, and how to keep it from happening again: that's the remainder of this page.
Petrol in a diesel: what does it do to the engine?
Two jobs fall to diesel on its route through a motor. Before it ignites, it lubricates — and then it ignites. Very fine clearances go into your injectors and the high-pressure fuel pump, and only your diesel flowing through keeps those surfaces from grinding together.
The second task petrol does not do at all, and the first it does badly. The rattling comes from petrol being made not to ignite when compressed, which is exactly the opposite of what a diesel needs. On top of that it is runnier than diesel, it strips away the lubrication the system rests on, and any pump working on such a mix is wearing itself.
Put those together and the shape of the trouble is clear. The harm is done by circulation, not by contact. All a tank with petrol in it amounts to is a fuel fault. Whatever a worn pump sheds travels on, carried by the fuel, into your injectors further along, which is why a pump that has been working on that petrol is where a mechanical issue starts.
How serious is petrol in a diesel? Four scenarios our engineers see in Slyne
Filled but not once started — as good as it gets. Only your tank has petrol in it, and so the job is draining the tank and flushing your system where the car stands. This situation can only really happen on a forecourt: anywhere else, your car got there by being driven.
Ignition on, or started for a moment. With the fuel system primed, the lines and filter now hold petrol that has come from that tank. Still normally simple: drain, flush, and the filter sorted.
Driven a few miles. Now your pump has spent these miles labouring on weakened fuel. Tank, lines, filter, then clean fuel run through the whole system: that is this work, and the way your car was driven matters as much as the mileage. On the school run to Slyne-with-Hest, St Luke's, Church of England Primary School, the distance is short. Getting as far as Lancaster, under 3 miles away, makes a very different task — as does any distance on the M6, under 3 miles from Slyne, with your engine working hard all the way.
Driven on till it complained — knocking, smoke, an uneven idle, a soft throttle. What you are hearing is the engine signalling fuel that no longer acts like diesel. Whether it is the verge on Main Road, a lay-by or a side road, stop where you are then leave it. The drain and flush still come first, and they deal with it: when a vehicle is pulled over early, lasting damage is very unusual.
Stories Slyne motorists hear about petrol in a diesel
It will not be fine. The myth: "Fill it the rest of the way with diesel and it will be." A fuller tank of the same mix is all you get, because topping up takes out nothing. Percentage is not how a diesel fuel system tolerates petrol, however much that guidance presumes.
Not so: a newer diesel copes with a bit of petrol. If anything, the reverse. Protection counts more on newer diesels, not less, because their fuel passes through smaller components at higher pressure.
"It starts, it drives, so there is no harm" — the myth that catches most motorists than any other. Feed diesel to a petrol motor and it usually won't run, and so the driver stops — and the harm stops with them. Whilst the pump grinds, a diesel fed petrol normally starts, ticks over and drives away as though nothing has happened. Fine and running are not the same thing.
An outdated workaround for a separate fault 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, that tank still contains the petrol.
Myth: "Drain that tank yourself and you are sorted." After the motor has run, some of that petrol is no longer in your tank: it's in the fuel filter and your lines, and it goes right back through your pump at the next start. And, a can of petrol drained by the kerbside is genuinely hazardous.
How it happens: petrol in a diesel
A careless moment is rarely the cause, and nobody means to do it. The petrol nozzle is the smaller of the two and slides into a diesel filler with almost no resistance; a diesel nozzle generally won't go into a petrol motor at all. The forecourt makes it simple, and the error runs one way.
The moment habit stops matching your car is the moment it takes place. A new vehicle, a hire car or a courtesy car. A household with one petrol and one diesel on the driveway. The pumps in a different order on a familiar forecourt. A rushed fill en route to Bare Lane with a train to catch. Years of petrol cars behind you, a diesel Volkswagen Golf in front of you at the forecourt for its first tank — that is when. Throw in rain, a phone call or a back seat full of children, and your hand does what it has always done.
Next time you fill up around Slyne: avoiding petrol in a diesel
- Not every forecourt in the UK keeps to green for unleaded and black for diesel, though most generally do. Check the petrol pump's label; the colour is just a clue.
- Check the filler flap. Plenty of cars state the fuel inside the flap or on the cap. Look at it on the first fill in a vehicle you don't know.
- A coloured fob or a sticker on your diesel's key achieves more than any amount of meaning to remember, in a household with one of each.
- "Diesel", aloud, before you pick up the nozzle — every time a new or hired car needs its first tank. It seems daft. It does the trick.
- Mistakes like this are easy to make whilst your mind is on something else, so your phone goes away.
- A misfuel inhibitor helps, up to a point. Some diesels come with a filler designed to reject a petrol nozzle, and add-on devices are available for motors without one. They are a safety net, not a reason to stop reading the pump.
- The moment you realise, stop: less petrol in that tank makes a weaker mix. What to do next doesn't change, though — still don't start the car.
Put petrol in a diesel in Slyne already?
Short and simple, then, is the order of things. Starting it is out, and so is switching on your ignition. Ask the attendants to help you roll it clear of the petrol pump if you are still on the forecourt, whether that's Esso or anywhere else. Next, 0333 366 0103. We'll ask what was put in, about how much, and if it has been run.
Say so if it was AdBlue rather than petrol: it's a separate fault, with its own page for Slyne, because AdBlue brings corrosion and deposits rather than lost lubrication.
Why one petrol in a diesel job around Slyne costs more than another
The four scenarios above are four different jobs, so no single price for this would be honest. Which of them you are in is mostly what moves the cost. Where the vehicle is matters too, and whether a technician can safely get to it, after the proportion of petrol to what that tank takes.
That's why we ask three queries before costing instead of after: what got in, how much, and if it has run. A range turns into a straight figure when those replies are in.
About Slyne, briefly
Slyne is a small village in Lancashire, situated near the coast and approximately 2.6 miles from Lancaster. Slyne sits at an elevation of around 45 metres, overlooking the surrounding countryside and the nearby coastline. Slyne has a mix of housing types, but semi-detached homes are the most common, and its population is around 582 residents. Slyne is close to other local places, including Hest Bank and Bolton-le-Sands.
Slyne and Lancashire: where our fuel drain cover runs
Petrol in diesel call-outs in Slyne — part of the LA postcode area — go to teams that likewise cover the locations about it, Hest Bank, Bolton Town End and Bolton-le-Sands included. The vehicle does not need to come to us: our engineers drain on a forecourt, in a supermarket car park, in a lay-by or on your own drive.
At the pump around Slyne, still?
No position is better: that is where you are. Ring, and leave it switched off.