How Worried Should You Be? Petrol in a Diesel Car in Mynydd Marian
Likely less than you are now — as long as no one has started the vehicle. Until the ignition primes the pump, the starter cranks, or the vehicle is driven, petrol in a diesel tank just rests there and does nothing. Which means the truthful reply to the first Mynydd Marian query — "have I ruined it?" — usually no. Petrol in Diesel is who to phone, with the engine kept off, so it remains that way. Keep reading for three things: the effect petrol has inside a diesel motor, the clues of how far it has got, and the way to make sure you don't repeat it.
Your engine and petrol in a diesel: what happens
On its way through an engine, diesel has two jobs. It protects to begin with, and only then does it burn. Your high-pressure pump and your injectors are made to extremely fine tolerances, and the diesel passing through them is what keeps those surfaces from wearing against one another.
Petrol does the first job badly and the second not at all. The rattling 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 runnier than diesel, it strips away the protection the fuel system hinges on, and any pump running on that blend is wearing itself.
Taken together, they make clear the shape the issue has. Not contact but circulation is what causes the damage. Petrol in a tank is a fuel problem. Whatever a worn pump sheds goes on, borne by your fuel, into the injectors further along, which is why a pump that has been working on the petrol is where a mechanical issue begins.
Mynydd Marian, petrol in a diesel: four situations, from mild to major
Filled up, and never started: no case is better. Just your tank has petrol in it, so the job is draining your tank and cleaning the fuel system where your car sits. This situation can only really occur on a forecourt: anywhere else, the vehicle got there by being driven.
A moment's running, or merely your ignition on. With the fuel system primed, the fuel lines and filter now hold petrol that came from that tank. That is generally still a simple task — a drain, a flush, and the fuel filter dealt with.
Driven a few miles. Now the pump has spent those miles labouring on thinned fuel. The work is your tank, the fuel lines, the fuel filter and fresh fuel through the entire system, and how hard the vehicle was driven counts as much as how far. On the school run to the local primary school, the mileage is short. Getting as far as St Asaph, under 10 miles away, makes a very different job — as does any distance on the Moreton Spur, under 25 miles from Mynydd Marian, with your engine labouring hard the whole time.
It protested, and only then stopped: smoke, clattering, a throttle gone soft, an idle gone lumpy. What you are hearing is your engine signalling fuel that no longer runs like diesel. Leave it where it stops: a lay-by, a quiet street, the verge on Pentregwyddel Road. What comes first is still the drain and flush, and that takes care of it, with long-term damage very unusual if a car is stopped early.
Myths Mynydd Marian drivers hear about petrol in a diesel
"Top it up the rest of the way with diesel and it will be fine" — a myth. It won't. Nothing is removed by topping up — you are left with a fuller tank, still the same mixture. The idea behind the advice — that diesel fuel systems tolerate petrol by percentage — is wrong.
If anything, the opposite holds. Myth: "A modern diesel can cope with a bit of petrol." Lubrication matters more on current diesels, not less, because their fuel runs through more precise components at higher pressure.
Myth: "If it starts and drives, there is no harm done." This is the one that catches people. Diesel in a petrol motor generally leaves a motor that won't run: the motorist stops, and so does the harm. Whilst the pump wears, a diesel fed petrol usually starts, idles and drives away as though nothing has happened. Running isn't the same as fine.
An outdated workaround for a different problem is behind this one. Myth: "Add some two-stroke oil and drive the car home." It does not put back what petrol has thinned, and that petrol is still in the tank after that.
Myth: "Drain the tank yourself and you're sorted." Once the engine has run, some of the petrol is no longer in that tank: it's in the fuel filter and your lines, and it goes straight back through your pump on your next start. Besides, petrol cleared into a can by the road is genuinely hazardous.
How petrol ends up: petrol in a diesel
It's seldom carelessness, and nobody does it on purpose. The forecourt makes it easy: the petrol nozzle is the smaller of the two, and it slips into a diesel filler with almost no resistance, whilst a diesel nozzle mostly won't go into a petrol vehicle at all. So the mistake runs one way.
Routine and your car getting out of step is how it happens. Courtesy car, hire car, or a car that's brand new. Two vehicles on one drive, one petrol, one diesel. The pumps in a different order on a well-known forecourt. Racing for a train at Colwyn Bay and filling up en route. Precisely the moment it happens: after years of driving petrol, a driver fills a diesel Renault Megane for the first time. The hand does what it has always done when you add rain, a phone call or a back seat full of children.
Next time you fill up around Mynydd Marian: avoiding petrol in a diesel
- Not every forecourt in the UK follows green for unleaded and black for diesel, even if most usually do. Read the petrol pump's label; the colour is only a hint.
- Plenty of vehicles state the fuel inside the filler flap or on the cap, so check there on the first fill in a vehicle you don't know.
- A coloured fob or a sticker on your diesel's key achieves more than any amount of intending to remember, in a home with one of each.
- It sounds daft and it works: on the first fill in a new or hired car, say "diesel" aloud before you take the nozzle off the petrol pump.
- Mistakes like this are easy to make while your mind is on something else, and so the phone goes away.
- Up to a point, a misfuel inhibitor helps: some diesels have a filler built to refuse a petrol nozzle, and add-on devices are available for the remainder. Count it as a backstop, and keep reading the petrol pump.
- Stop the moment you realise. Less petrol in your tank makes a thinner mixture. It does not change what to do next, which is still not to fire it up.
Petrol already in a diesel around Mynydd Marian? Start here
The order of things is brief, then. Leave it unstarted, with your ignition off as well. Ask the staff to help you push it away from the pump if you're still on the forecourt, whether that is Shell or somewhere else. What was put in, about how much, and whether it has run: tell us that when you ring 0333 366 0103.
Corrosion and deposits form the problem with AdBlue, whereas petrol brings lost protection. So if it was AdBlue, say so — and read its own Mynydd Marian page.
One petrol in a diesel job in Mynydd Marian costs more than another. Why?
Four separate jobs lie behind the four scenarios above — which is why there's no fair single price. Which of them you are in is mostly what moves the cost. Two things come after that: the petrol that went in as a proportion of what that tank holds, then the place your car is in and whether a technician can get to it safely.
Before any quote, not after, we ask three queries: your fuel that got in, the amount, and if it has run. That is why. The answers turn a range into a straight figure.
About Mynydd Marian and its setting
Mynydd Marian is a small village in Conwy, situated on the north Wales coast, with a mix of semi-detached housing and scenic views. Mynydd Marian sits at an elevation of 174 metres, overlooking the surrounding countryside and the Irish Sea. Mynydd Marian is close to nearby villages such as Llysfaen and Penmaen Rhos, and is within commuting distance of St Asaph.
Mynydd Marian and Conwy: where our fuel drain cover runs
Llysfaen, Bryn Dulas and Penmaen Rhos are among the places around Mynydd Marian that the same vans work, answering petrol in diesel call-outs across Mynydd Marian's LL postcode area. You need not bring the vehicle to us. Forecourts, supermarket car parks, lay-bys and your own drive are all locations where we work.
Mynydd Marian: still at the pump?
Then you're in the best position there is. Switched off it remains; then call.