Central: Petrol in a Diesel Car? How Worried to Be
Unstarted? Then less anxious than you probably are. Everyone around Central begins with "have I ruined it?", and the honest answer is usually no: petrol resting in your tank of a diesel remains harmless until priming, cranking or driving pulls it into the fuel system. Keep it like that: leave your motor off and phone Petrol in Diesel. Further down, you will find what petrol really does inside a diesel, how far it may have gone, and how to stop it happening to you a second time.
What petrol in a diesel does to the engine
On its way through a motor, diesel has two jobs. It burns, and before it burns it protects. What stops the surfaces inside the high-pressure pump and the fuel injectors from wearing down against one another is the diesel flowing through them — they're designed to very fine tolerances.
Petrol does the first job poorly and the second not at all. The knocking comes from petrol being made not to ignite when compressed, which is precisely the reverse of what a diesel needs. On top of that it is runnier than diesel, it strips out the lubrication the fuel system hinges on, and any pump running on that mixture is wearing itself.
Put these together and the shape of the trouble is plain. Not contact but movement is what causes the harm. A tank with petrol in it is a fuel fault. 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 your fuel to the fuel injectors further on.
Petrol in a diesel around Central: how bad is it? Four cases
Filled but not once started — as good as it gets. Being at a forecourt is what makes this the case: elsewhere, the vehicle has been driven there to begin with. With that petrol kept inside that tank alone, it is emptied and rinsed right where it stands, and nothing more is needed.
The ignition switched on, or a short start. The fuel system has been bled, and so petrol has left your tank and got to the fuel filter and the fuel lines. That is generally still a simple job — a drain, a flush, and the fuel filter seen to.
A couple of miles driven, and your pump has spent every one of them labouring on diluted fuel. Distance is only half of it; how hard it was driven counts just as much. Either way this work runs to the tank, the lines, the fuel filter and fresh fuel through the whole circuit. Driving the children to the local primary school is one kind of trip. Any distance on the M4, under 5 miles from Central, means your engine has worked hard throughout, and a run to Cardiff, under a mile away, makes a very different task too.
It protested, and only then stopped: smoke, knocking, a throttle gone soft, an idle gone lumpy. The engine is telling you the fuel is no longer acting like diesel. Stop wherever you are — the verge on Westgate Street, a lay-by, a side street — and leave the car where it is. The drain and flush still come first, and they deal with it: if a car is stopped soon, lasting damage is very unusual.
Petrol in a diesel myths Central drivers hear
False: topping up to full with diesel makes it fine. It does not. Topping up removes nothing; it gives you a fuller tank of the same mixture. That advice presumes a diesel fuel system tolerates petrol by percentage. It does not.
If anything, the reverse holds. Myth: "A modern diesel can cope with a bit of petrol." Finer parts and higher pressure are how a current diesel runs its fuel, and that makes the protection matter more, not less.
The myth that catches people off guard: if it starts and drives, it must be unharmed. Feed diesel to a petrol motor and it usually will not run, so the motorist stops — and the damage stops with them. Nothing looks to have happened when a diesel fed petrol fires up, ticks over and drives away, as it usually does; meanwhile your pump grinds. Running doesn't mean fine.
Myth: "Add some two-stroke oil and drive the vehicle home." It is an old workaround for a separate problem. What petrol has thinned remains weakened, and that petrol stays in that tank anyway.
The next start sends petrol back round the pump out of the lines and your filter, where some of that ends up after the motor has run. That's why a DIY tank drain does not leave you sorted — a myth. And, a can of petrol filled at the roadside is genuinely risky.
How it happens: petrol in a diesel
It is seldom carelessness, and nobody does it on purpose. A diesel nozzle mostly won't fit a petrol motor, but the smaller petrol nozzle goes into the filler of a diesel nearly without resistance — so forecourts make this one error simple, and just in that direction.
When routine and the car stop matching, it takes place. A new vehicle, a hire car or a courtesy car. Households running one of each, petrol and diesel. A forecourt you know, only with its pumps arranged differently. Filling up in a hurry en route to Cardiff Central, with a train to catch. The first fill-up in a diesel Skoda Octavia after years of driving petrol is exactly the moment it takes place. With rain, a call arriving, or a car full of children to deal with, the hand simply does what it has always done.
Next time you fill up around Central: preventing petrol in a diesel
- Not every forecourt in the UK keeps to green for unleaded and black for diesel, even if most generally do. Check the petrol pump's label; the colour is just a hint.
- Many cars state the fuel inside the filler flap or on the cap, and so check it on the first fill in a car you do not know.
- A coloured fob or a sticker on the diesel's key achieves more than any amount of meaning to remember, for a home with one of each.
- Before the nozzle leaves the pump the first time you fuel a hired or new vehicle, say "diesel" out loud. Daft, perhaps, but it works.
- Mistakes like this are simple to make while your mind is on something else, so your phone goes away.
- A misfuel inhibitor helps, up to a point. Some diesels come with a filler built to block a petrol nozzle, and add-on devices exist for motors without one. They are a safety net, not a reason to stop reading the petrol pump.
- Noticing it mid-fill? Stop there and then. A thinner mixture results from less petrol inside that tank, but the next stage remains the same: don't start it.
Central: already put petrol in a diesel?
Then the order of things is short. Don't switch the ignition on, and don't start it. Ask the attendants to help you roll it clear of the petrol pump if you are still on the forecourt, whether that's Texaco or anywhere else. Then ring 0333 366 0103 and tell us what was put in, about how much, and whether it's run.
AdBlue, not petrol? Then tell us. Corrosion and deposits, not lost protection, make it a separate problem — Central has a page all for it.
What makes one Central petrol in a diesel task cost more than the next
There's no honest single price for this, since the four situations above are four separate jobs. Which of them you are in is chiefly what shifts your cost. Two things come after that: the petrol that got in as a proportion of what your tank holds, then the place your car is in and whether a van can reach it safely.
That is why our engineers ask three queries before pricing instead of after: what was put in, how much, and whether it's run. Those answers change a range into a straight figure.
About Central
Central is a suburban area located on the coast in Cardiff, with an elevation of 16 metres above sea level. Central sits adjacent to the city centre, approximately 0.2 miles from Cardiff, and is surrounded by nearby places such as Cathays Park and Riverside. Central is characterised by predominantly flat-type housing, accommodating a population of around 6140 residents. Central is also relatively close to the Welsh capital's amenities and attractions, while being 131.3 miles from London.
Fuel drain cover across Cardiff, Central included
Cardiff, Cathays Park and Riverside are among the places around Central that the same vans work, answering petrol in diesel call-outs across Central's CF postcode area. A forecourt, a supermarket car park, a lay-by or your own drive are all places our engineers drain, and your vehicle doesn't need to come to us.
Central: still at the pump?
Then you are in the best place there is. Call, and keep it turned off.