Cae-maes-y-bar: Petrol in a Diesel Car? How Worried to Be
Likely less than you already are — as long as no one has started the car. Petrol resting in a diesel tank does nothing to the engine till something draws it through your fuel system — the ignition priming your pump, your starter, or the drive on its own. So the fair answer to the first query everyone around Cae-maes-y-bar asks, "have I ruined it?", is usually no. Leave the motor off and ring Petrol in Diesel — that keeps it like that. The remainder of this page covers what petrol actually does to a diesel, how to tell how far it has got, and how to make sure it doesn't happen to you again.
Inside the engine: what petrol in a diesel does
On its way through a motor, diesel does two tasks. It combusts, and before it combusts it protects. Built to very fine clearances, the injectors and the pump depend on your diesel flowing through them to keep their surfaces from wearing against one another.
Petrol does the first task badly and the second not at all. Being less viscous than diesel, petrol strips away the lubrication a fuel system needs, so a pump running on that mixture wearing itself. It's equally made to resist igniting under compression — the opposite of what a diesel needs — which is where you hear the clattering.
Together, those make the shape of the issue clear. The harm is done by movement, not by contact. Any tank with petrol in it is a fuel issue. A pump that has been running on that petrol is the beginning of a mechanical one, and whatever a worn pump sheds travels on with your fuel to the injectors further on.
Petrol in a diesel around Cae-maes-y-bar: how bad is it? Four cases
Fuelled but not once started — the best it gets. Being on a forecourt is what makes this possible: elsewhere, your car has been driven there to begin with. With that petrol kept in your tank alone, it is cleared and cleaned on the spot, and nothing more is needed.
Started for a moment, or only the ignition on. With the fuel system primed, the fuel lines and filter already hold petrol that came from that tank. Usually little more than emptying, flushing and sorting your filter, and so still simple.
Your pump has spent a few miles on thinned fuel — that is what driving the car meant. Mileage is only half of it; how hard it was driven counts equally. Either way the work runs to your tank, the fuel lines, the fuel filter and fresh fuel through the whole system. Driving the kids to the local primary school is one sort of trip. Getting as far as Swansea, under 5 miles away, makes a very different job — as does any mileage on the M4, under a mile from Cae-maes-y-bar, with your engine working hard all the way.
It protested, and only then stopped: smoke, rattling, a throttle gone soft, an idle gone ragged. That's your engine telling you its fuel has stopped acting like diesel. Whether it's the verge on Nantyffin Road, a lay-by or a side road, stop there then leave it. What comes first is still the fuel drain and flush, and that deals with it, with long-term damage very rare if a car is stopped quickly.
Cae-maes-y-bar motorists and the petrol in a diesel myths they hear
Myth: "Fill it the rest of the way with diesel and it will be fine." It will not. Nothing is removed when you top up — that tank simply holds more of the same blend. That guidance supposes a diesel fuel system tolerates petrol by percentage. It does not.
Myth: "A newer diesel can cope with a bit of petrol." If anything, the reverse. At higher pressure, through finer components: that is how a newer diesel handles its fuel, so the protection counts for more, not less.
The myth that catches motorists out: if it starts and drives, it must be unharmed. Diesel in a petrol motor usually leaves a motor that will not run: the driver stops, and so does the damage. Nothing seems to have happened when a diesel fed petrol fires up, ticks over and drives away, which it usually will; meanwhile the pump wears. Being able to run isn't proof of being fine.
Myth: "Add some two-stroke oil and drive the car home." It is an old fix for a distinct problem. The petrol is still in the tank after that, and whatever it has diluted isn't put back.
If your engine has been run, part of the petrol sits in the filter and the lines, not the tank — and the next start sends it right back through your pump. So the myth "drain the tank yourself and you're sorted" doesn't hold. It's also genuinely dangerous to drain petrol into a can by the roadside.
How petrol ends up: petrol in a diesel
No one does it on purpose, and it is seldom carelessness. A diesel nozzle generally will not go into a petrol motor, but the smaller petrol nozzle goes into the filler of a diesel nearly without resistance — so forecourts make this one error straightforward, and just in one direction.
The moment routine stops matching the car is the moment it occurs. A new car, a hire car or a courtesy car. A household with one petrol and one diesel on the drive. The pumps in a different order on a well-known forecourt. A rushed fill on the way to Llansamlet with a train to catch. A new-to-you diesel Volkswagen Golf, its first fuelling, and a motorist used to petrol: exactly when it happens. Throw in rain, a phone call or a back seat full of children, and the hand repeats what it has always done.
Next time you fill up in Cae-maes-y-bar: avoiding petrol in a diesel
- Green for unleaded and black for diesel is usual in the UK — but not on every forecourt. Go by the label on the petrol pump, not the colour.
- In a car you do not know, look inside the flap over your filler or at the cap before the first fill: plenty of cars state the fuel there.
- Mark the key. In a house with one of each, a coloured fob or a sticker on the diesel's key does more than any amount of meaning to remember.
- It seems silly and it does the trick: on your first fill in a new or hired car, say "diesel" out loud before you take the nozzle off the pump.
- Put your phone away. This is an easy mistake to make while you are thinking about something else.
- A misfuel inhibitor helps, up to a point. Some diesels have a filler built to block a petrol nozzle, and add-on devices are available for vehicles without one. They are a backstop, not a reason to stop checking the pump.
- Stop as soon as you realise. Less petrol in the tank means a thinner mixture. It does not change what to do next, which is still not to crank it.
Already put petrol in a diesel around Cae-maes-y-bar?
The order of things is short, then. Don't turn your ignition on, and do not crank it. Ask the staff to help you push it clear of the petrol pump if you're still at the forecourt, whether that is Tesco or anywhere else. Next, 0333 366 0103. We'll ask what got in, roughly how much, and if it has been run.
Say so if it was AdBlue instead of petrol: it's a separate issue, with its own page for Cae-maes-y-bar, since AdBlue brings corrosion and deposits rather than lost lubrication.
Why one petrol in a diesel task around Cae-maes-y-bar costs more than another
Four different jobs lie behind the four scenarios above — which is why there's no fair single quote. The situation itself does most of the work of moving your cost. Beyond that it is the ratio — how much petrol was put in against how much that tank holds — and after that where the car is and whether a technician can get to it safely.
That's why our engineers ask three questions before quoting rather than after: what got in, how much, and if it's run. Their replies are what turn a range into one firm number.
About Cae-maes-y-bar and where it is
Cae-maes-y-bar is a small suburban area located near the coast in Swansea, with a mix of terraced housing and local amenities. Cae-maes-y-bar sits at an elevation of 23 metres, close to the nearby communities of Pwllygrafel and Llansamlet. Cae-maes-y-bar is situated approximately 3 miles from Swansea city centre, making it a convenient residential location. Cae-maes-y-bar has a population of around 1187 people, according to recent estimates.
Across Swansea and around Cae-maes-y-bar: fuel drain cover
The vans answering petrol in diesel jobs around Cae-maes-y-bar, in the SA postcode area, also work the places around it, Pwllygrafel, Llansamlet and Felin Newydd included. The car does not need to come to us: we drain at a forecourt, in a supermarket car park, in a lay-by or on your own drive.
Still at the petrol pump in Cae-maes-y-bar?
Nothing beats it: that is where you are. Keep it off. Phone.