Penygroes: Petrol in a Diesel Car? How Worried to Be
Not started? Then less anxious than you likely are. Petrol resting in a diesel tank does nothing to the motor till something draws it through your fuel system — your ignition priming your pump, your starter, or driving on its own. So the fair answer to the first question everyone around Penygroes asks, "have I ruined it?", is normally no. To keep the car that way, ring Petrol in Diesel then leave the motor switched off. What petrol really does to a diesel, how to gauge how far it's travelled, and how to stop it from happening a second time: that's the rest of this page.
Petrol in a diesel: what does it do to your engine?
Passing through an engine, diesel is doing two things at once. It protects to begin with, and only then does it burn. Designed to extremely fine clearances, the fuel injectors and your pump rely on the diesel moving through them to stop their surfaces wearing against one another.
Of these two tasks, petrol handles the first poorly and the second not at all. A pump running on a petrol mix is wearing itself out, because petrol is runnier than diesel and strips out the lubrication the fuel system depends on. Petrol is also made to resist igniting under compression — the reverse of what a diesel needs from its fuel — and that is where the clattering starts.
Put these together and the shape of the problem is clear. It is movement that does the harm, not contact. A tank with petrol in it is a fuel issue. The start of a mechanical problem is a pump that has been running on that petrol — and whatever a worn pump sheds travels on with your fuel to your injectors beyond it.
Petrol in a diesel in Penygroes: how bad is it? Four cases
The best case there is: filled up, never started. Only the tank has petrol in it, and so the task is clearing the tank and cleaning the fuel system where your car sits. This scenario can only truly take place on a forecourt: anywhere else, your car got there by being driven.
Ignition on, or started for a second. The fuel system has been bled, and so petrol has left the tank and reached the filter and the fuel lines. Drain, flush, deal with your filter: still usually straightforward.
Some miles driven, and your pump has spent each of them running on diluted fuel. Tank, lines, filter, then fresh fuel run through the whole system: that is the work, and the way your car was driven counts as much as the miles. Short trips, such as the school run to the local primary school, are one matter. Getting as far as Bangor, under 15 miles away, makes a very different job — as does any mileage on the Moreton Spur, over 50 miles from Penygroes, with the motor running hard all the way.
It protested, and only then stopped: smoke, clattering, a throttle gone soft, an idle gone ragged. The fuel is not behaving like diesel any more, and the engine is saying so. Whether it's the verge on Heol y Bedyddwyr, a lay-by or a side road, stop where you are and leave it. The drain and flush still go first, and they sort it out: if a car is pulled over soon, long-term damage is very uncommon.
What Penygroes 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 will be fine" — a myth. It will not. Topping up takes out nothing; it gives you a fuller tank of the same mixture. That advice presumes a diesel fuel system tolerates petrol by percentage. It doesn't.
"Current diesels can handle a little petrol" — a myth, and closer to the reverse. At higher pressure, through more precise parts: that is how a newer diesel moves its fuel, so the lubrication matters for more, not less.
The myth that catches drivers out: if it starts and drives, it must be unharmed. Diesel in a petrol motor normally leaves a motor that will not run: the driver stops, and so does the harm. Feed petrol to a diesel and it normally fires up, idles and pulls away as if nothing happened — all while its pump is wearing. Fine and running aren't the same thing.
Myth: a two-stroke additive makes it safe to drive home. It is an old workaround, meant for another problem. The petrol is still in that tank after that, and whatever it has weakened isn't put back.
If the engine has run, part of that petrol is in the fuel filter and the lines, not the tank — and the next start sends it straight back through your pump. So the myth "drain that tank yourself and you're sorted" does not hold. Emptying petrol into a can by the roadside is also genuinely dangerous.
Why petrol in a diesel occurs at all
A careless moment is seldom the cause, and nobody means to do it. The forecourt makes it simple: the petrol nozzle is the narrower of the two, and it slips into a diesel filler with almost no resistance, whilst a diesel nozzle mostly will not go into a petrol vehicle at all. So the slip runs one way.
The moment routine stops matching your car is the moment it takes place. Hire cars, courtesy cars, and cars that are new to you. Households running one of each, petrol and diesel. A forecourt you know, only with its pumps arranged differently. A rushed fill en route to Criccieth with a train to catch. Exactly the moment it happens: after years of driving petrol, a driver fills a diesel Volkswagen Golf for the first time. Throw in a back seat full of children, a phone call or rain, and the hand wins.
Penygroes people: how to avoid petrol in a diesel next time
- Check the petrol pump, not the colour. In the UK unleaded handles are usually green and diesel black, but not on every forecourt. The label is what matters.
- In a motor you don't know, look inside the flap over your filler or at the cap before your first fill: many vehicles print the fuel type there.
- A coloured fob or a sticker on the diesel's key does more than any amount of meaning to remember, in a home with one of each.
- Before the nozzle comes off the pump the first time you fuel a hired or new motor, say "diesel" aloud. Daft, perhaps, but it works.
- While you're thinking about something else, this is an easy mistake to make — so tuck your phone away.
- Add-on devices exist for cars without one, and some diesels are built with a filler that will not take a petrol nozzle. Helpful — but a backstop only, never a reason to stop checking the label.
- As soon as you notice, stop: less petrol inside that tank makes a thinner mix. What to do next doesn't change, though — still don't crank it.
Penygroes: already put petrol in a diesel?
Short and simple, then, is the order of things. Do not crank it, and do not turn your ignition on. Ask the staff to help you push it clear of the petrol pump if you are still on the forecourt, whether that's the nearest petrol station or somewhere else. Next, 0333 366 0103. We'll ask what was put in, roughly how much, and if it has been run.
Say so if it was AdBlue rather than petrol: it is a separate fault, with its own page for Penygroes, because AdBlue brings corrosion and deposits rather than lost protection.
One petrol in a diesel task in Penygroes costs more than another. Why?
Four different jobs sit behind the four scenarios above — which is why there is no honest single price. Which of them you're in is chiefly what shifts your cost. Two things come after that: the petrol that went in as a share of what that tank holds, then the place the vehicle is in and whether a technician can reach 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. The replies turn a range into a straight figure.
About Penygroes itself
Penygroes is a village in Gwynedd, situated in a coastal area of northwest Wales, with an elevation of 113 metres. Penygroes lies near the towns of Llanllyfni, Talysarn, and Nebo, and is approximately 13.6 miles from Bangor. Penygroes has a population of around 1505 people, predominantly living in terraced housing. Penygroes is located about 205.6 miles from London, making it a relatively remote village in the UK.
Fuel drain cover around Penygroes and across Gwynedd
Petrol in diesel call-outs around Penygroes — part of the LL postcode area — go to teams that also cover the spots about it, Llanllyfni, Talysarn and Nebo among them. A forecourt, a supermarket car park, a lay-by or your own drive are all spots we drain, and your vehicle doesn't need to move to us.
Still at the pump around Penygroes?
No position is better: that's where you are. Keep it off. Call.