Should You Worry? Petrol in a Diesel Car in Little Shelford
Provided it hasn't been started, worry less than you likely are. Petrol resting in a diesel tank does nothing to the engine till something pulls it through the system — your ignition priming your pump, the starter, or the drive itself. So the honest answer to the first query everyone around Little Shelford asks, "have I ruined it?", is usually no. To leave the car that way, phone Petrol in Diesel and leave your engine switched off. The rest of this page covers what petrol really does to a diesel, how to judge how far it has got, and how to make sure it does not happen to you again.
Petrol in a diesel: what does it do to the engine?
Passing through a motor, diesel does two jobs at once. It combusts, and before it ignites it lubricates. Designed to very fine clearances, the fuel injectors and your pump depend on the diesel flowing through them to keep their surfaces from wearing against one another.
The second task petrol doesn't do at all, and the first it does badly. It's runnier than diesel and strips away the protection the system depends on, and so a pump running on a petrol mixture is a pump wearing itself. And petrol is made to resist igniting under compression, which is the reverse of what a diesel needs from its fuel. That is where the clattering comes from.
Combined, those make the shape of the trouble clear. Not contact but circulation is what does the damage. All a tank with petrol in it amounts to is a fuel issue. After the pump has been working on that petrol, a mechanical issue has started: whatever is shed by a pump that is wearing travels onward to the injectors with the fuel.
Little Shelford, petrol in a diesel: four situations, from mild to serious
The best case there is: filled up, not once started. Just your tank has petrol in it, so the job is emptying that tank and purging the fuel system where your car stands. This situation can only really take place at a forecourt: anywhere else, the car got there by being driven.
The ignition switched on, or a short start. The system has been bled, and so petrol has left your tank and got to the filter and the fuel lines. Still generally easy: drain, flush, and the filter sorted.
Those few miles driven meant your pump labouring on fuel weakened by petrol throughout. Miles is only half of it; how hard it was driven counts equally. Either way the work runs to the tank, the lines, your filter and clean fuel through the whole circuit. Driving the kids to Great and Little Shelford CofE (Aided) Primary School is one kind of trip. Very different once more: a trip to Cambridge, under 5 miles away, or any mileage on the M11, under a mile from Little Shelford, where your engine never stopped working hard.
Clattering, a lumpy idle, smoke, a throttle gone soft: driven until it complained. The engine is telling you the fuel is no longer acting like diesel. Pull up wherever you are — the verge on Garden Fields, a lay-by, a side street — and leave the vehicle where it is. Long-term damage is very uncommon if a car is stopped early, and the drain and flush that still go first take care of it.
What Little Shelford people get told about petrol in a diesel — and the stories in it
"Top it up the rest of the way with diesel and it'll be fine" — a myth. It won't. Nothing comes out when you top up — that tank just holds more of the same blend. That advice supposes a diesel fuel system handles petrol by percentage. It does not.
"Newer diesels can handle a little petrol" — a myth, and closer to the reverse. At higher pressure, through more precise components: that's how a modern diesel handles its fuel, so the lubrication matters more, not less.
"It starts, it drives, so no harm done" — the myth that trips up more drivers than any other. A petrol engine fed diesel generally will not run, and so the motorist stops and the harm stops with them. Feed petrol to a diesel and it generally starts, idles and drives away as if nothing has happened — all while its pump is wearing. Fine and running aren't the same at all.
Not so: a two-stroke additive lets you to drive home. It was an old workaround, meant for another problem. What petrol has weakened stays diluted, and the petrol remains in the tank regardless.
The next start sends petrol back round the pump out of your lines and the fuel filter, where some of that ends up once the engine has been run. That is why draining the tank yourself does not sort it — a myth. It's also truly hazardous to drain petrol into a can by the roadside.
How it happens: petrol in a diesel
No one does it on purpose, and it is rarely carelessness. One way only, because of the nozzles: the slimmer petrol one slips inside a diesel filler with almost no resistance, while the diesel one generally will not fit a petrol vehicle. That is how the forecourt makes it simple.
It happens when habit and your car stop matching. A new vehicle, a hire car or a courtesy car. One petrol and one diesel on the driveway of the same household. The pumps in a different order on a familiar forecourt. A hurried fill en route to Shelford with a train to catch. Precisely the moment it occurs: after years of driving petrol, a driver fills a diesel Volkswagen Golf for the first time. The hand does what it has always done when you add rain, a phone call or a back seat full of kids.
Preventing petrol in a diesel next time you fill up around Little Shelford
- Check the pump, not the colour. In the UK unleaded handles are generally green and diesel black, yet not on every forecourt. The label is what counts.
- In a car you do not know, look inside the flap over your filler or at the cap before the first fill: many cars print the fuel type there.
- A coloured fob or a sticker on the diesel's key achieves more than any amount of meaning to remember, for a household with one of each.
- It sounds silly and it does the trick: on your first fill in a new or hired car, say "diesel" out loud before you lift the nozzle off the petrol pump.
- While you're thinking about something else, this is an easy mistake to make — so put the phone away.
- Some diesels come with a filler built to block a petrol nozzle, and devices you can add exist for vehicles without one. Such an inhibitor helps up to a point — as a safety net, not a reason to stop reading the petrol pump.
- Stop the moment you notice. Less petrol in your tank makes a thinner mix. It does not change what to do next, which is still not to crank it.
Put petrol in a diesel around Little Shelford already?
The order of things is short, then. Do not crank it, and don't turn the ignition on. Ask the staff to help you roll it away from the petrol pump if you are still at the forecourt, whether that is Esso or somewhere else. Phone 0333 366 0103 next, with three facts — the fuel, the approximate volume, and if it has run.
Say so if it was AdBlue instead of petrol: it's a different issue, with its own page for Little Shelford, because AdBlue brings corrosion and deposits rather than lost protection.
One petrol in a diesel task in Little Shelford costs more than another. Why?
There is no fair single price for this, because the four scenarios above are four separate jobs. Mostly, your cost moves with which situation you're in. Where your car is counts too, and whether a technician can safely get to it, after the ratio of petrol to what your tank holds.
That is why our engineers ask three queries before pricing rather than after: what went in, how much, and whether it's run. With those answers, there is a straight figure rather than a range.
About Little Shelford and its setting
Little Shelford is a small village in Cambridgeshire, situated on the River Cam and near the city of Cambridge. Little Shelford has a low elevation of around 19 metres and is surrounded by nearby places such as Hauxton and Great Shelford. Little Shelford is characterized by its predominantly detached housing stock and is located approximately 45 miles from London. Little Shelford remains a quiet residential community with a population of around 534 people.
Across Cambridgeshire and around Little Shelford: fuel drain cover
Hauxton, Freestones Corner and Great Shelford are among the spots near Little Shelford that the same teams work, answering petrol in diesel jobs across Little Shelford's CB postcode area. A forecourt, a supermarket car park, a lay-by or your own driveway are all locations our technicians work, and the vehicle doesn't need to move to us.
Still at the pump in Little Shelford?
No position is better: that is where you are. Phone, and keep it switched off.