Should You Worry? Petrol in a Diesel Car in Gurnos
Unstarted? Then less anxious than you probably feel. Until your ignition primes your pump, the starter turns, or the vehicle is driven, petrol in a diesel tank simply rests there and does no harm. Which makes the truthful reply to the first Gurnos question — "have I ruined it?" — usually no. Leave the motor off and ring Petrol in Diesel — that is how you keep it that way. Further down, you will find what petrol really does inside a diesel, how far it might have got, and how to stop it happening to you again.
Petrol in a diesel: what does it do to the motor?
Two jobs fall to diesel on its journey round a motor. Lubricating comes before burning; it does both. Very fine tolerances go into the injectors and the high-pressure pump, and only your diesel flowing through stops those surfaces grinding together.
Poorly at the first, not at all at the second: that is petrol. Being less viscous than diesel, petrol strips away the protection a fuel system needs, so a pump running on that mixture to wear itself. It is equally made to resist igniting under compression — the reverse of what a diesel needs — which is where you get the clattering.
The shape of the issue is plain once you put those together. It is circulation that does the harm, not contact. Petrol in the tank is a fuel fault. After your pump has been labouring on that petrol, a mechanical problem has begun: whatever is shed by a pump that is grinding travels onward to the injectors with the fuel.
Four scenarios our engineers see in Gurnos: how serious is petrol in a diesel?
The best case there is: filled up, not once started. Being on a forecourt is what makes this the case: elsewhere, your car has been driven there to begin with. With that petrol kept in your tank alone, it is cleared and purged on the spot, and nothing more is needed.
A brief spell of running, or just the ignition on. With the fuel system primed, your lines and filter already hold petrol that has come from your tank. Still usually easy: drain, flush, and your filter seen to.
A couple of miles driven, and your pump has spent each of them working on diluted fuel. Tank, lines, filter, then clean fuel run through the whole circuit: that is the work, and the way the vehicle was driven counts as much as the distance. Short trips, like the school run to the local primary school, are one matter. Any mileage on the M4, under 10 miles from Gurnos, means your engine has worked hard throughout, and a run to Swansea, under 15 miles away, is a very different job as well.
Driven on until it complained — rattling, smoke, a ragged idle, a dead throttle. What you are hearing is the motor signalling fuel that no longer acts like diesel. Stop where you are — on the verge on Woodlands Business Park, at the kerb, down a side road — and don't move it. A car stopped quickly very seldom has long-term damage, as the drain and the flush, which still go first, take care of it.
What Gurnos drivers get told about petrol in a diesel — and the stories in it
False: topping up to full with diesel makes it fine. It doesn't. Nothing is removed by topping up — you are left with a bigger tank, still the same mix. That advice assumes a diesel fuel system handles petrol by percentage. It doesn't.
Myth: "A newer diesel can cope with a bit of petrol." If anything, the opposite. Finer parts and higher pressure are how a modern diesel runs its fuel, and that makes the lubrication count more, not less.
The myth that catches people out: if it starts and drives, it must be unharmed. Diesel in a petrol motor generally means a motor that won't run: the driver stops, and so does the harm. A diesel fed petrol normally starts, ticks over and drives away as though nothing has happened, whilst your pump wears. Running isn't the same as fine.
An outdated workaround for a different problem lies behind this one. Myth: "Add some two-stroke oil and drive it home." What petrol has weakened remains diluted, and that petrol stays in the tank regardless.
Once the motor has run, part of the petrol sits in your filter and the fuel lines, not your tank — and your next start pulls it right back through the pump. So the myth "drain your tank yourself and you're sorted" does not hold. Clearing petrol into a can by the roadside is also genuinely dangerous.
Why petrol in a diesel happens so easily
A careless moment is rarely the cause, and no one means to do it. One way only, since of the nozzles: the slimmer petrol one slips inside a diesel filler with almost no resistance, while the diesel one mostly won't fit a petrol car. That's how the forecourt makes it easy.
Routine and the car getting out of step is how it happens. Courtesy car, hire car, or a vehicle that's new. Households running one of each, petrol and diesel. The pumps in a different order on a well-known forecourt. A rushed fill on the way to Neath with a train to catch. The first fill-up in a diesel Renault Megane after years of driving petrol is precisely the moment it takes place. Add rain, a phone call or a back seat full of kids, and the hand does what it has always done.
How to avoid petrol in a diesel on your next fill-up in Gurnos
- Read the petrol pump, not the colour. In the UK unleaded handles are generally green and diesel black, yet not on every forecourt. The label is what counts.
- The first fill in an unfamiliar vehicle is the time to check the filler flap — on it, or on the cap, plenty of motors state which fuel they take.
- A coloured fob or a sticker on your diesel's key achieves more than any amount of meaning to remember, in a home with one of each.
- It seems silly and it works: on your first fill in a new or hired car, say "diesel" out loud before you lift the nozzle off the pump.
- Thinking about something else is when this becomes an easy mistake to make, and so put your phone away then keep your mind on the petrol pump.
- A misfuel inhibitor helps, up to a point. Some diesels have a filler designed 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.
- As soon as you notice, stop: less petrol in that tank means a thinner mix. What to do next does not change, though — still don't crank it.
Petrol already in a diesel around Gurnos? Begin here
Then the order of things is brief. Don't crank it, and don't switch your ignition on. Ask the attendants to help you roll it away from the pump if you are still at the forecourt, whether that is Tesco or anywhere else. Next, 0333 366 0103. We will ask what was put in, about how much, and if it's been run.
Corrosion and deposits form the trouble with AdBlue, whereas petrol means lost lubrication. So if it was AdBlue, say so — and read its own Gurnos page.
One petrol in a diesel job around Gurnos costs more than another. Why?
Four different jobs sit behind the four situations above — which is why there is no honest single quote. Which of them you're in is chiefly what moves your cost. The proportion counts next, meaning how much of your tank is petrol, and then the location of the vehicle and whether reaching it is safe for our van.
Three queries come first, before any quote, instead of after — what went in, how much, has it run — and that is the reason. Their answers are what change a range into one firm number.
About Gurnos and its setting
Gurnos is a village situated on the banks of a river in Powys, Wales, with an elevation of around 75 metres. Gurnos lies near the communities of Ystalyfera, Glan-rhyd, and Gorof, and is approximately 12.5 miles from Swansea. Gurnos has a population of around 1208 people and predominantly consists of semi-detached housing. Gurnos is located in a rural area, relatively close to the urban centre of Swansea.
Across Powys and around Gurnos: fuel drain cover
Gurnos waits in the SA postcode area, and our vans that answer petrol in diesel call-outs there work the spots near it as well — Ystalyfera, Glan-rhyd and Gorof among them. The car does not need to come to us: we drain on a forecourt, in a supermarket car park, in a lay-by or on your own drive.
Gurnos: still at the petrol pump?
Then you are in the best spot there can be. Ring, and keep it turned off.