Dwygyfylchi: Petrol in a Diesel Car? How Worried to Be
Provided it hasn't been started, you can worry less than you probably are. Petrol sitting in a diesel tank does nothing to your engine until something draws it through the system — your ignition priming the pump, your starter, or driving itself. So the fair answer to the first question everyone around Dwygyfylchi asks, "have I wrecked it?", is normally no. Keep it that way: leave your motor off and call Petrol in Diesel. Read on for three things: the effect petrol has inside a diesel motor, the signs of how far it has spread, and the way to make sure you don't repeat it.
Inside the engine: what petrol in a diesel really does
Two jobs fall to diesel on its route round a motor. It protects first, and after that does it burn. What stops the surfaces inside your high-pressure pump and your injectors from grinding against one another is your diesel flowing through them — they are designed to extremely fine tolerances.
Petrol does the first task poorly and the second not at all. Being less viscous than diesel, petrol strips out the protection a fuel system needs, so a pump running on the mixture to wear itself. It's equally made to resist igniting under compression — the reverse of what a diesel needs — which is why you get the rattling.
Put these together and the shape of the problem is clear. Contact doesn't do the harm — movement does. All a tank with petrol in it amounts to is a fuel problem. The start of a mechanical one is a pump that has been running on that petrol — and whatever a worn pump sheds moves on with the fuel to the injectors beyond it.
Four situations our engineers see in Dwygyfylchi: how serious is petrol in a diesel?
Fuelled but never started — the best it gets. That petrol is in that tank and only that tank, and the task is a drain and a flush where your car sits. This is the one scenario that can only really happen on a forecourt, as anywhere else the car has been driven to get there.
The ignition turned on, or a brief start. Your system has been bled, so petrol has left the tank and got to your filter and the fuel lines. That's normally still a straightforward task — a drain, a flush, and the fuel filter seen to.
Driven a couple of miles. Now the pump has spent those miles labouring on diluted fuel. Mileage is only half of it; how hard it was driven matters just as much. Either way the work runs to your tank, the lines, the filter and fresh fuel through the whole system. Short trips, like the school run to the local primary school, are one thing. Any distance on the Moreton Spur, under 50 miles from Dwygyfylchi, means the motor has worked hard throughout, and a run to Bangor, under 15 miles away, is a very different job as well.
Driven until it complained. Knocking, a lumpy idle, smoke, a throttle that has gone soft. The fuel isn't behaving like diesel any more, and the motor is saying so. Whether it's the verge on Cae Gwynan, a lay-by or a side street, stop where you are and leave it. What goes first is still the fuel drain and flush, and that takes care of it, with permanent damage very uncommon if a vehicle is stopped soon.
What Dwygyfylchi people get told about petrol in a diesel — and the myths in it
False: topping up to full with diesel makes it fine. It doesn't. Nothing is removed by topping up — you're left with a bigger tank, still the same mixture. The idea behind the advice — that diesel fuel systems accept petrol by percentage — is wrong.
Myth: "A modern diesel can cope with a bit of petrol." If anything, the reverse. A modern diesel sends its fuel through smaller parts at higher pressure, which makes the lubrication count more, not less.
This is the one that catches drivers. Myth: "If it starts and drives, there's no harm done." Feed diesel to a petrol motor and it generally won't run, so the motorist stops — and the harm stops with them. Whilst the pump wears, a diesel fed petrol normally starts, ticks over and drives away as though nothing has happened. Running isn't the same as fine.
An outdated fix for a different issue lies behind this one. Myth: "Add some two-stroke oil and drive it home." It does not put back what petrol has weakened, and the petrol is still inside that tank after that.
"Drain it yourself and you are sorted" — a myth, because after it has been running some petrol sits in the fuel filter and lines, ready to go right back through your pump on the next start. Besides, petrol drained into a can by the road is genuinely dangerous.
How petrol ends up: petrol in a diesel
It is rarely carelessness, and nobody does it on purpose. One way only, because of the nozzles: the slimmer petrol one slides inside a diesel filler with almost no resistance, whereas the diesel one mostly won't fit a petrol vehicle. That's how the forecourt makes it easy.
The moment routine stops matching the vehicle is the moment it occurs. Any motor that is new to you — hired, on loan as a courtesy car, or brand new. One petrol and one diesel on the drive of the same household. The pumps in a different order on a well-known forecourt. A train to catch, and a rushed fill en route to Penmaenmawr. Years of petrol motors behind you, a diesel Volkswagen Passat in front of you on the forecourt for its first tank — that's when. With rain, a call arriving, or children to deal with, your hand just does what it always has.
Avoiding petrol in a diesel next time you fill up around Dwygyfylchi
- Read the pump, not the colour. In the UK unleaded handles are generally green and diesel black, yet not on each forecourt. The label is what counts.
- Many vehicles state the fuel inside the filler flap or on the cap, so check there on the first fill in any motor you do not know.
- Mark your key. In a home with one of each, a coloured fob or a sticker on the diesel's key does more than any amount of meaning to remember.
- Say it before you lift it. On your first fill in a new or hired car, say "diesel" out loud before you take the nozzle off the petrol pump. It sounds silly and it works.
- While you're thinking about something else, this is an easy mistake to make — so put the phone away.
- A misfuel inhibitor helps, up to a point. Some diesels have a filler designed to refuse a petrol nozzle, and add-on devices exist for vehicles without one. They are a backstop, not a reason to stop reading the pump.
- The moment you realise, stop: less petrol in your tank makes a weaker mix. What to do next doesn't change, though — still don't fire it up.
Dwygyfylchi: already put petrol in a diesel?
In that case, there is only a short order of things. Starting it is out, and so is switching on the ignition. The attendants at the forecourt — whether at Shell itself or wherever you filled up — will usually help roll it clear of the pump if you ask. Then ring 0333 366 0103 and tell us what was put in, roughly how much, and whether it's run.
AdBlue, not petrol? Then tell us. Corrosion and deposits, not lost lubrication, make it a separate issue — Dwygyfylchi has a page just for it.
What makes one Dwygyfylchi petrol in a diesel task cost more than the next
A fair single price doesn't exist here: four situations, four separate jobs. What shifts the cost is mostly which of them you are in. After that it is the ratio — how much petrol got in against how much that tank holds — and after that where the vehicle is and whether a van can get to it safely.
Before any quote, not after, we ask three questions: your fuel that was put in, the volume, and if it's run. That's why. Given those answers, there is a straight figure instead of a range.
About Dwygyfylchi
Dwygyfylchi is a coastal village in Conwy, Wales, situated near the towns of Penmaenmawr and Bangor. Dwygyfylchi lies at an elevation of 29 metres, close to the Irish Sea, and is surrounded by nearby places such as St Gwynans and Capelulo. Dwygyfylchi has a population of around 1403 people, predominantly living in semi-detached housing. Dwygyfylchi is located approximately 200.5 miles from London, but is more closely linked to the nearby city of Bangor, which is 10.2 miles away.
Across Conwy and in Dwygyfylchi: fuel drain cover
Dwygyfylchi rests in the LL postcode area, and the vans that answer petrol in diesel jobs there work the locations near it as well — St Gwynans, Capelulo and Penmaenmawr among them. The vehicle doesn't need to move to us: we drain at a forecourt, in a supermarket car park, in a lay-by or on your own drive.
In Dwygyfylchi and still at the petrol pump?
No position is better: that's where you are. Ring, and keep it turned off.