Should You Worry? Petrol in a Diesel Car in Turvey
Not started? Then less worried than you probably feel. Everyone around Turvey begins with "have I ruined it?", and the fair answer is normally no: petrol resting in the tank of any diesel remains harmless until priming, cranking or driving draws it into the system. To leave the car that way, ring Petrol in Diesel then leave your engine alone. Read on for three things: the effect petrol has inside a diesel engine, the clues of how far it has spread, and the way to make sure you never do it again.
Petrol in a diesel: what does it do to the motor?
Diesel does two jobs on its way through an engine. Lubricating comes before burning; it does both. Built to extremely fine clearances, the injectors and your pump rely on your diesel flowing through them to keep their surfaces from wearing against one another.
Badly at the first, not at all at the second: that is petrol. A pump working on a petrol mix is wearing itself out, since petrol is thinner than diesel and takes away the lubrication the fuel system relies on. Petrol is also made to resist igniting under compression — the reverse of what a diesel wants from its fuel — and that is where the clattering comes.
The shape of the trouble is clear when you put those together. Contact doesn't do the damage — circulation does. Where the petrol is only inside that tank, it's a fault of fuel, nothing more. After your pump has been running on that petrol, a mechanical problem has started: whatever is shed by a pump that's wearing down is carried onward to the injectors with your fuel.
Four situations we see in Turvey: how bad is petrol in a diesel?
Filled up, and not started: no case is better. Being on a forecourt is what makes this possible: elsewhere, your car has been driven there to begin with. With the petrol kept in that tank alone, it's emptied and rinsed on the spot, and nothing more is needed.
Started for a moment, or only the ignition on. Petrol has left the tank and got to the fuel filter and your lines, since your system has been primed. Usually nothing more than draining, purging and sorting your filter, so still straightforward.
Some miles driven, and your pump has spent each of them running on weakened fuel. Tank, lines, filter, then fresh fuel put through the entire system: that's this work, and the way the vehicle was driven matters as much as the mileage. On the school run to Turvey Primary School, the mileage is small. Very different a second time: a trip to Milton Keynes, under 15 miles away, or some mileage on the M1, under 10 miles from Turvey, where the motor kept working hard.
Clattering, a lumpy idle, smoke, a throttle gone soft: driven until it complained. What you are hearing is the motor signalling fuel that no longer acts like diesel. Stop wherever you are — the verge on High Street, a lay-by, a side street — then leave the vehicle there. A car stopped quickly very rarely has permanent damage, as the fuel drain and the flush-through, which still come first, take care of it.
Stories Turvey drivers hear about petrol in a diesel
Myth: topping up to full with diesel makes it fine. It does not. Nothing is removed by topping up — you are left with a bigger tank, still the same mix. Percentage is not how a diesel fuel system copes with petrol, whatever that guidance assumes.
"Newer diesels can handle a little petrol" — a myth, and closer to the opposite. A current diesel runs its fuel through finer components at higher pressure, which makes the protection count more, not less.
Myth: "If it starts and drives, there's no damage done." This is the one that fools people. The driver of a petrol engine fed diesel usually stops, because it will not run, and the harm stops there. Whilst your pump wears, a diesel fed petrol usually starts, idles and drives away as if nothing has happened. Running doesn't mean fine.
An old fix for a separate problem lies behind this one. Myth: "Add some two-stroke oil and drive it home." What petrol has diluted remains thinned, and the petrol stays inside the tank regardless.
If the engine has run, part of the petrol sits in the filter and the fuel lines, not the tank — and the next start pulls it straight back through the pump. So the myth "drain that tank yourself and you are sorted" doesn't stand up. And, a can of petrol filled by the roadside is truly hazardous.
How it happens: petrol in a diesel
It's rarely carelessness, and no one does it on purpose. 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 generally won't go into a petrol vehicle at all. So the mistake runs one way.
When habit and the car stop matching, it happens. Courtesy car, hire car, or a car that's brand new. One petrol and one diesel on the driveway of the same household. A forecourt you know, only with its pumps arranged differently. Racing for a train at Bedford and fuelling up en route. A new-to-you diesel Renault Clio, its first fuelling, and a motorist used to petrol: exactly when it occurs. With rain, a call arriving, or children to deal with, your hand simply does what it has always done.
Next time you fill up in Turvey: preventing petrol in a diesel
- Green for unleaded and black for diesel is usual in the UK — but not on every forecourt. Trust the label on the petrol pump, not the colour.
- In a motor you do not know, look inside the flap over your filler or at the cap before the first fill: plenty of motors state the fuel type there.
- One of each in the home? Label the key to your diesel — a coloured fob, a sticker — since meaning to remember is not enough.
- Say it before you lift it. On your first fill in a new or hired car, say "diesel" out loud before you take the nozzle off the petrol pump. It seems silly and it does the trick.
- Mistakes like this are simple to make while your mind is on something else, and so the phone goes away.
- Up to a point, a misfuel inhibitor helps: some diesels have a filler built to refuse a petrol nozzle, and add-on devices are available for the rest. Treat it as a backstop, then keep checking the petrol pump.
- Less petrol means a thinner mix, and so stop the moment you realise — while remembering that the next step is unchanged. It's still not to fire it up.
Already put petrol in a diesel in Turvey?
Then, there is only a short order of things. Starting it is out, and so is turning on the ignition. If you are still at the forecourt — Applegreen or anywhere else — ask the staff to help you roll the vehicle clear of the pump. Then call 0333 366 0103 and tell us what got in, roughly how much, and whether it's run.
Say so if it was AdBlue instead of petrol: it's a separate issue, with its own page for Turvey, since AdBlue brings corrosion and deposits instead of lost protection.
Turvey petrol in a diesel tasks: why one costs more than another
The four situations above are four separate tasks, so no single price for this would be fair. The scenario itself does most of the work of moving the cost. Where the vehicle is matters too, and whether a technician can safely get to it, after the ratio of petrol to what your tank holds.
Three questions come first, before quoting, rather than after — what was put in, how much, has it run — and that is the reason. A range turns into a straight figure once those answers are in.
About Turvey
Turvey is a village in Bedfordshire, situated on the banks of the River Great Ouse at an elevation of around 55 metres. Turvey lies approximately 49.9 miles north of London and 10 miles east of Milton Keynes, with nearby villages including Cold Brayfield and Newton Blossomville. Turvey has a population of around 931 people, predominantly living in semi-detached housing. Turvey is surrounded by a rural landscape, with the Emmaus Village Carlton nearby.
Fuel drain cover across Bedfordshire, Turvey included
The teams answering petrol in diesel call-outs in Turvey, in the MK postcode area, equally work the locations near it, Cold Brayfield, Newton Blossomville and Emmaus Village Carlton among them. The car does not need to move to us: our technicians drain on a forecourt, in a supermarket car park, in a lay-by or on your own drive.
In Turvey and still at the petrol pump?
The best place there is, then — that is where you are. Turned off it remains; then call.