Should You Worry? Petrol in a Diesel Car in Laira
Far less than you probably are, if it hasn't been started. Petrol sitting in a diesel tank does nothing to your motor till something draws it through your fuel system — your ignition priming your pump, the starter, or the drive on its own. So the truthful answer to the first question anyone around Laira asks, "have I wrecked it?", is usually no. Petrol in Diesel is who to ring, with the motor kept off, so it stays that way. What petrol actually does to a diesel, how to judge how far it's travelled, and how to keep it from happening a second time: that is the rest of this page.
Petrol in a diesel: what does it do to your engine?
Diesel has two jobs on its way through an engine. It combusts, and before it combusts it protects. What stops the surfaces inside the high-pressure fuel pump and the injectors from grinding against one another is your diesel flowing through them — they're built to extremely fine tolerances.
Poorly at the first, not at all at the second: that is petrol. Being less viscous than diesel, petrol strips out the lubrication a fuel system needs, so a pump on the mixture to wear itself. It is equally made to resist igniting under compression — the opposite of what a diesel needs — which is why you hear the rattling.
Together, those leave the shape of the trouble clear. The damage is done by circulation, not by contact. Any tank with petrol in it is a fuel problem. A pump that has been working on that petrol is the beginning of a mechanical one, and whatever a worn pump sheds moves on with the fuel to the fuel injectors further on.
How bad is petrol in a diesel? Four scenarios our technicians see in Laira
Filled up, not once started. The best case there can be. Being at a forecourt is what makes this possible: elsewhere, your car has been driven there to begin with. With that petrol kept inside that tank alone, it is emptied and rinsed on the spot, and nothing more is needed.
The ignition turned on, or a brief start. The fuel system has been bled, and so petrol has left that tank and got to the filter and your lines. Still normally simple: drain, flush, and the fuel filter dealt with.
Driven a couple of miles. Now the pump has spent these miles running on thinned fuel. How hard your car was driven matters as much as how far, and this work takes in that tank, the fuel lines, the fuel filter and fresh fuel through the entire system. The school run to Laira Green Primary School is one thing. Any mileage on the M5, under 50 miles from Laira, means the engine working hard throughout, and a run to Plymouth, under 3 miles away, makes a very different job as well.
It protested, and only then stopped: smoke, rattling, a throttle gone soft, an idle gone lumpy. What you are hearing is the motor signalling fuel that no longer behaves like diesel. Leave it where it has stopped: a lay-by, a side street, the verge on Old Laira Road. Permanent damage is very unusual if a car is stopped early, and the drain and flush-through that still go first deal with it.
What Laira people get told about petrol in a diesel — and the myths in it
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 copes with petrol, however much that guidance supposes.
Myth: "A modern diesel can cope with a bit of petrol." If anything, the opposite. Smaller parts and higher pressure are the way a modern diesel runs its fuel, and that makes the protection count more, not less.
The myth that catches motorists off guard: if it starts and drives, it must be unharmed. The motorist of a petrol engine fed diesel usually stops, because it will not run, and the damage stops with them. Feed petrol to a diesel and it normally starts, idles and pulls away like nothing happened — all the while its pump wears. Fine and running are not the same at all.
An old fix for a distinct problem is behind this one. Myth: "Add some two-stroke oil and drive it home." That petrol is still inside the tank afterwards, and whatever it has weakened isn't put back.
If the motor has run, part of that petrol sits in your filter and the lines, not the tank — and your next start sends it right back through the pump. So the myth "drain that tank yourself and you are sorted" does not hold. And, a can of petrol filled at the kerbside is genuinely dangerous.
How petrol ends up: petrol in a diesel
On purpose? Never. Through carelessness? Rarely, if ever. 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 mistake runs one way.
When routine and the car stop matching, it takes place. Any motor that's new to you — a hire car, on loan as a courtesy car, or just bought. Two cars on one drive, one petrol, one diesel. A forecourt you know, only with its pumps laid out differently. A train to catch, and a rushed fill en route to Plymouth. Years of petrol cars 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 at your next fill-up around Laira
- Green for unleaded and black for diesel is normal in the UK — but not on every forecourt. Go by the label on the petrol pump, not the colour.
- Inspect your filler flap. Plenty of motors state the fuel type inside the flap or on the cap. Look at it on the first fill in any car you do not know.
- One of each in the household? Label your key to the diesel — a coloured fob, a sticker — because meaning to remember isn't enough.
- Say it before you lift it. On the first fill in a new or hired car, say "diesel" aloud before you lift the nozzle off the petrol pump. It seems silly and it does the trick.
- Mistakes like this are straightforward to make while your mind is on something else, so the phone goes away.
- Up to a point, a misfuel inhibitor helps: some diesels have a filler built to block a petrol nozzle, and aftermarket devices exist for the remainder. Count it as a backstop, and keep reading the petrol pump.
- Spotting it halfway? Stop there and then. A thinner blend follows from less petrol inside the tank, yet your next step remains the same: don't start it.
Laira: already put petrol in a diesel?
In that case, there is only a short order of things. Starting it is out, and so is turning on your ignition. The staff on the forecourt — whether at Esso itself or wherever you filled up — will normally help push it away from the pump if you ask. Then call 0333 366 0103 and tell us what was put in, about how much, and if it has run.
AdBlue, not petrol? Then tell us. Corrosion and deposits, not lost lubrication, make it a separate issue — Laira has a page just for it.
One petrol in a diesel task around Laira costs more than another. Why?
There's no honest single quote for this, since the four scenarios above are four separate jobs. The scenario itself does most of the work of moving the cost. The ratio matters next, meaning how much of your tank is petrol, and then the position of the car and whether getting to it is safe for our van.
Three questions come first, before any quote, rather than after — what went in, how much, has it run — and this is the reason. Their answers are what change a range into one firm number.
About Laira and where it is
Laira is a coastal suburban area in Devon, situated near the city of Plymouth and close to the neighbouring areas of Efford and Lipson Vale. Laira lies at an elevation of around 25 metres, with semi-detached housing being the predominant type of accommodation in the area. Laira is located approximately 1.8 miles from Plymouth, making it a convenient residential location for those working in the city. Laira has a population of around 6851 residents, according to approximate estimates.
Fuel drain cover across Devon, Laira included
Our vans answering petrol in diesel jobs around Laira, in the PL postcode area, also work the spots around it, Efford, Lipson Vale and Mount Gould among them. The car does not need to come to us: our engineers drain at a forecourt, in a supermarket car park, in a lay-by or on your own drive.
At the pump around Laira, still?
Then you are in the best position there can be. Ring, and keep it turned off.