Prestatyn: Petrol in a Diesel Car? How Worried to Be
Unstarted? Then less worried than you likely feel. Till the ignition primes your pump, the starter turns, or the vehicle is driven, petrol in a diesel tank just sits there and does nothing. Which makes the truthful reply to that first Prestatyn query — "have I wrecked it?" — normally no. Leave the motor off and ring Petrol in Diesel — that keeps it that way. What petrol actually does to a diesel, how to gauge how far it's gone, and how to keep it from happening a second time: that is the remainder of this page.
The motor and petrol in a diesel: what happens
Passing through a motor, diesel is doing two jobs at the same time. It ignites, and before it ignites it lubricates. Your high-pressure pump and the injectors are built to extremely fine gaps, and your diesel passing through them is what stops those surfaces from wearing against one another.
Petrol handles the first job poorly and the second not at all. The rattling comes from petrol being made not to ignite when compressed, which is exactly the reverse of what a diesel needs. On top of that it is thinner than diesel, it strips away the lubrication your system hinges on, and any pump running on such a blend is wearing itself.
Together, those leave the shape of the problem plain. The harm is done by movement, not by contact. Petrol in the tank is a fuel fault. The beginning of a mechanical one is a pump that has been labouring on that petrol — and whatever a worn pump sheds travels on with the fuel to the injectors downstream.
Four situations our engineers see around Prestatyn: how serious is petrol in a diesel?
Fuelled, and not started: nothing beats it. Being on a forecourt is what makes this the case: elsewhere, the car has been driven there to begin with. With that petrol kept inside that tank alone, it's emptied and rinsed right where it stands, and nothing more is needed.
A moment's running, or just the ignition on. The fuel system has been bled, and so petrol has left the tank and reached the fuel filter and the fuel lines. Still generally straightforward: drain, flush, and the filter seen to.
Driven a couple of miles. Now the pump has spent these miles working on thinned fuel. Tank, lines, filter, then fresh fuel run through the whole system: that is the work, and the way the car was driven counts as much as the mileage. The school run to the local primary school is one matter. Very different a second time: a run to St Asaph, under 10 miles away, or some distance on the Moreton Spur, under 15 miles from Prestatyn, where the motor never stopped labouring hard.
Driven on till it protested — knocking, smoke, a ragged idle, a dead throttle. The fuel isn't behaving like diesel any more, and your motor is telling you. Pull up wherever you are — the verge on Nant Hall Road, a lay-by, a side street — and leave it where it is. Lasting damage is very uncommon when a vehicle is pulled over early, and the fuel drain and flush-through that still go first sort it out.
What Prestatyn people get told about petrol in a diesel — and the myths in it
"Top it up the rest of the way with diesel and it'll be fine" — a myth. It will not. Nothing is removed by topping up — you're left with a fuller tank, still the same mixture. A diesel fuel system does not accept petrol by percentage in the way that guidance assumes.
"Newer diesels can handle a little petrol" — a myth, and closer to the opposite. Finer components and higher pressure are the way a current diesel runs its fuel, and that makes the lubrication matter more, not less.
One myth that catches people out: if it starts and drives, it must be unharmed. Feed diesel to a petrol engine and it normally will not run, so the driver stops — and the harm stops with them. Nothing looks to have happened when a diesel fed petrol fires up, ticks over and drives away, as it usually will; meanwhile your pump wears. Fine and running aren't the same thing.
An old workaround for a distinct problem is behind this one. Myth: "Add some two-stroke oil and drive the car home." What petrol has thinned stays weakened, and that petrol remains inside your tank anyway.
The next start sends petrol back round the pump from the fuel lines and your filter, where some of it sits once your engine has been run. That is why a DIY tank drain doesn't sort it — a myth. It is also really dangerous to drain petrol into a can at the kerbside.
How does petrol in a diesel occur?
A careless moment is seldom the cause, and no one means to do it. The petrol nozzle is the slimmer of the two and slides into a diesel filler with almost no resistance; a diesel nozzle generally will not go into a petrol car at all. The forecourt makes it simple, and the error runs one way.
When habit and the car stop matching, it occurs. A new vehicle, a hire car or a courtesy car. A household with one petrol and one diesel on the driveway. Your usual forecourt, its pumps suddenly in a different order. A train to catch, and a hurried fill on the way to the nearest station. A new-to-you diesel Volkswagen Passat, its first fuelling, and a motorist accustomed to petrol: precisely when it occurs. Your hand does what it has always done once you add rain, a phone call or a back seat full of kids.
Prestatyn people: how to avoid petrol in a diesel next time
- The label is what matters, and so read the pump instead of the colour: in the UK unleaded handles are usually green and diesel black, but not on every forecourt.
- In a vehicle you do not know, look inside the flap over the filler or at the cap before your first fill: plenty of vehicles print the fuel there.
- One of each in the household? Label the key to the diesel — a bright fob, a sticker — because intending to remember isn't enough.
- It seems daft and it works: on the first fill in a new or hired car, say "diesel" out loud before you lift the nozzle off the petrol pump.
- Mistakes like this are simple to make while your mind is on something else, and so your phone goes away.
- A misfuel inhibitor helps, up to a point. Some diesels have a filler built to reject a petrol nozzle, and add-on devices exist for motors without one. They are a safety net, not a reason to stop checking the petrol pump.
- The moment you realise, stop: less petrol inside that tank makes a thinner blend. What to do next does not change, though — still don't start the vehicle.
Put petrol in a diesel around Prestatyn already?
Then the order of things is brief. Starting it is out, and so is turning on your ignition. Still at the forecourt, at Tesco or anywhere else? Ask the attendants to help you roll the vehicle away from the petrol pump. Next, 0333 366 0103. We will ask what was put in, about how much, and if it has been run.
Say so if it was AdBlue rather than petrol: it is a separate issue, with its own page for Prestatyn, since AdBlue brings corrosion and deposits instead of lost protection.
One petrol in a diesel job in Prestatyn costs more than another. Why?
There's no fair single quote for this, since the four situations above are four different tasks. Mostly, the cost shifts with which one you are in. Where the car is matters too, and whether our van can safely reach it, after the share of petrol to what the tank holds.
What went in, how much, and whether it has run — three questions our technicians ask before pricing, not after, for precisely that reason. Their replies are what turn a range into one firm number.
About Prestatyn and where it is
Prestatyn is a coastal town in Denbighshire, Wales, situated at a low elevation of around 10 metres above sea level. Prestatyn lies near the towns of St Asaph and Rhyl, and is close to the villages of Gwaenysgor and Meliden. Prestatyn has a mix of housing types, but is predominantly characterised by detached homes. Prestatyn is located approximately 187 miles from London, making it a popular destination for those seeking a more relaxed pace of life.
Across Denbighshire and around Prestatyn: fuel drain cover
Prestatyn rests in the LL postcode area, and our teams that answer petrol in diesel call-outs there work the places around it as well — Woodland Park, Gwaenysgor and Meliden among them. The vehicle doesn't need to come to us: our technicians drain on a forecourt, in a supermarket car park, in a lay-by or on your own driveway.
In Prestatyn and still at the petrol pump?
Then you are in the best position there can be. Call, and leave it switched off.