Petrol in a Diesel Car in Cyncoed: How Worried Should You Be?
Probably less than you are now — as long as no one has started the vehicle. "Have I wrecked it?" is the first thing anyone in Cyncoed asks, and the truthful answer is normally no, because petrol left in a diesel tank hurts nothing until it's drawn through the fuel system — by ignition priming, by the starter, or by driving. To leave the car that way, call Petrol in Diesel then leave the engine switched off. Further down, this page sets out what petrol actually does inside a diesel, how far it might have got, and how to stop it happening to you a second time.
What petrol in a diesel does to your engine
On its way through a motor, diesel has two tasks. Before it ignites, it protects — and then it combusts. What stops the surfaces inside the high-pressure pump and the fuel injectors from wearing against each other is the diesel passing through them — they are designed to extremely fine clearances.
The second task petrol doesn't do at all, and the first it does badly. The knocking comes from petrol being designed not to ignite when compressed, which is precisely the reverse of what a diesel needs. On top of that it is thinner than diesel, it strips away the lubrication the fuel system hinges on, and any pump working on that blend is wearing itself.
Taken together, they show the shape the issue takes. Not contact but movement is what does the harm. All a tank with petrol in it amounts to is a fuel problem. A pump that has been labouring on that petrol is the start of a mechanical one, and whatever a worn pump sheds moves on with the fuel to the fuel injectors downstream.
Four situations we see in Cyncoed: how serious is petrol in a diesel?
Fuelled, and never started: no case is better. Being on a forecourt is what makes this the case: elsewhere, the vehicle has been driven there to begin with. With that petrol kept inside your tank alone, it's cleared and rinsed on the spot, and nothing more is needed.
Your ignition switched on, or a short start. Petrol has come out of that tank and reached the fuel filter and your lines, because your system has been primed. That is usually still a simple task — a drain, a flush, and your filter dealt with.
Driven a couple of miles. Now your pump has spent those miles working on thinned fuel. How hard the car was driven counts as much as how far, and this work takes in the tank, the lines, your filter and fresh fuel through the whole circuit. A school run to the local primary school is one matter. Any distance on the M4, under 3 miles from Cyncoed, means the engine working hard throughout, and a run to Cardiff, under 3 miles away, is a very different job too.
It protested, and only then stopped: smoke, rattling, a throttle gone soft, an idle gone lumpy. That's your engine telling you its fuel no longer is acting like diesel. Leave it wherever it has stopped: a lay-by, a quiet street, the verge on Cyncoed Road. A vehicle pulled over quickly very rarely has lasting damage, as the drain and the flush-through, which still come first, sort it out.
Cyncoed drivers and that petrol in a diesel myths they hear
"Top it up the rest of the way with diesel and it will be fine" — a myth. It will not. Nothing comes out when you top up — that tank just carries more of the same blend. That advice supposes a diesel fuel system handles petrol by percentage. It doesn't.
Myth: a modern diesel copes with a bit of petrol. Rather, the opposite. Lubrication counts more on modern diesels, not less, since their fuel passes through more precise components at higher pressure.
"It starts, it drives, and so there is no harm" — the myth that trips up most people than any other. The driver of a petrol motor fed diesel usually stops, because it will not run, and the harm stops there. A diesel fed petrol generally starts, ticks over and drives away as if nothing has happened, whilst your pump grinds. Running doesn't mean fine.
An outdated workaround for a distinct problem lies behind this one. Myth: "Add some two-stroke oil and drive the car home." None of what petrol weakened is put back by it — and later, your tank still contains that petrol.
"Drain it yourself and you are sorted" — a myth, since after it has been running some petrol sits in the fuel filter and lines, ready to go straight back through the pump at your next start. And, a can of petrol filled at the kerbside is truly risky.
Petrol in a diesel: how does it occur?
A careless moment is seldom the cause, and nobody means to do it. A diesel nozzle generally won't fit a petrol car, but the smaller petrol nozzle goes into the filler of a diesel almost without resistance — so forecourts make this one error simple, and just in one direction.
The moment routine stops matching the car is the moment it takes place. A new motor, a hire car or a courtesy car. A household with one petrol and one diesel on the driveway. Your usual forecourt, its pumps now in a different order. A train to catch, and a rushed fill en route to Heath High Level. A new-to-you diesel Volkswagen Passat, its first fuelling, and a driver accustomed to petrol: precisely when it occurs. The hand does what it has always done once you add rain, a phone call or a back seat full of children.
Next time you fill up in Cyncoed: preventing petrol in a diesel
- The label is what counts, and so read the petrol pump instead of the colour: in the UK unleaded handles are normally green and diesel black, but not on every forecourt.
- Plenty of motors state the fuel inside your filler flap or on the cap, and so check there on the first fill in any car you don't know.
- A coloured fob or a sticker on the diesel's key does more than any amount of intending to remember, for a house with one of each.
- Say it before you lift it. On your first fill in a new or hired car, say "diesel" aloud before you take the nozzle off the petrol pump. It seems daft and it works.
- Put the phone away. This is an easy mistake to make whilst you're thinking about something else.
- A misfuel inhibitor helps, up to a point. Some diesels come with a filler built to reject a petrol nozzle, and add-on devices exist for vehicles without one. They are a safety net, not a reason to stop reading the petrol pump.
- As soon as you notice, stop: less petrol inside your tank means a thinner blend. What to do next does not change, though — still don't fire it up.
Already put petrol in a diesel in Cyncoed?
The order of things is short, then. Never crank it, and don't switch the ignition on. Yet at the forecourt, at Texaco or anywhere else? Ask the staff to help you roll it clear of the petrol pump. Next, 0333 366 0103. We will ask what went in, roughly how much, and if it's been run.
Say so if it was AdBlue instead of petrol: it's a different fault, with its own page for Cyncoed, because AdBlue brings corrosion and deposits rather than lost lubrication.
Why one petrol in a diesel job in Cyncoed costs more than another
The four situations above are four different tasks, so no single price for this would be fair. Which of them you are in is mostly what shifts the cost. Next it is the share — how much petrol went in against how much that tank holds — and after that where your car is and whether a technician can get to it safely.
Three queries come first, before any quote, instead of after — what went in, how much, has it run — and that is the reason. Their answers are what change a range into one firm number.
About Cyncoed itself
Cyncoed is a suburban area in Cardiff, situated approximately 2.7 miles from the city centre and near the coast. Cyncoed is characterised by its predominantly detached housing stock and sits at an elevation of around 64 metres. Cyncoed is close to nearby places such as Llanedeyrn, Roath Park, and Pentwyn, and is home to a population of around 5855 residents.
Across Cardiff and around Cyncoed: fuel drain cover
Llanedeyrn, Roath Park and Pentwyn are among the locations near Cyncoed that the same teams work, answering petrol in diesel jobs across Cyncoed's CF postcode area. The car 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 driveway.
Still at the petrol pump around Cyncoed?
Then, you could not be in a better position. Turned off it remains; then call.