Penyrheol: Petrol in a Diesel Car? How Worried to Be
Unstarted? Then less anxious than you probably feel. Petrol resting in a diesel tank does nothing to your engine until something draws it through the system — your ignition priming your pump, the starter, or driving on its own. So the fair answer to the first query anyone around Penyrheol asks, "have I wrecked it?", is normally no. To leave the car that way, call Petrol in Diesel then leave the motor switched off. Below, this page sets out what petrol really does inside a diesel, how far it may have gone, and how to stop it happening to you again.
Petrol in a diesel: what does it do to your engine?
Diesel does two jobs on its way through an engine. Before it ignites, it lubricates — and then it burns. Built to very fine tolerances, your injectors and the pump rely on the diesel moving through them to keep their surfaces from wearing against one another.
Badly at the first, not at all at the second: that is petrol. Being less viscous than diesel, petrol strips out the lubrication a fuel system needs, so a pump running on the mixture wearing itself. It's also made to resist igniting under compression — the opposite of what a diesel needs — which is why you hear the knocking.
The shape of the problem is plain once you put those together. Not contact but circulation is what does the damage. Petrol in a tank is a fuel fault. Once the pump has been labouring on that petrol, a mechanical problem has started: whatever is shed by a pump that is wearing is carried downstream to the fuel injectors with your fuel.
Four scenarios our engineers see around Penyrheol: how bad is petrol in a diesel?
The best case there can be: filled up, never started. Only that tank has petrol in it, so the job is clearing the tank and flushing your system where the car sits. This situation can only really occur on a forecourt: anywhere else, your car got there by being driven.
The ignition turned on, or a short start. The fuel system has been bled, so petrol has left the tank and got to your filter and the fuel lines. Still normally straightforward: drain, flush, and the filter sorted.
Those few miles on the road were the pump labouring on fuel weakened by petrol throughout. Mileage is only half of that; how hard it was driven matters equally. Either way the work includes that tank, your lines, the filter and fresh fuel through the whole circuit. The school run to the local primary school is one matter. Driving as far as Swansea, under 10 miles away, makes a very different job — as does any miles on the M4, under 3 miles from Penyrheol, with your engine running hard all the way.
Rattling, a lumpy idle, smoke, a throttle gone soft: driven until it complained. What you are hearing is your engine signalling fuel that no longer runs like diesel. Leave it wherever it has stopped: a lay-by, a side street, the verge on Clos Vernon Watkins. What goes first is still the fuel drain and flush, and that takes care of it, with lasting damage very rare if a car is pulled over quickly.
Penyrheol people and the petrol in a diesel myths they hear
False: topping up to full with diesel makes it fine. It doesn't. Topping up removes nothing; it gives you a bigger tank of the same mixture. The assumption behind that advice — that diesel fuel systems accept petrol by percentage — is wrong.
Not so: a newer diesel copes with a bit of petrol. If anything, the opposite. A current diesel runs its fuel through more precise components at higher pressure, which makes the protection count more, not less.
Myth: "If it starts and drives, there's no harm done." This is the one that catches people. 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 grinds, a diesel fed petrol usually starts, ticks over and drives away as though nothing has happened. Being able to run isn't the same as being fine.
Myth: "Add some two-stroke oil and drive it home." It is an outdated workaround for a separate problem. The petrol is still in your tank afterwards, and what it has thinned is not put back.
Once the motor has run, part of the petrol is in the filter and the lines, not the tank — and the next start pulls it right back through your pump. So the myth "drain the tank yourself and you're sorted" doesn't stand up. And, a can of petrol filled at the roadside is genuinely dangerous.
How does petrol in a diesel happen?
It's seldom carelessness, and no one does it on purpose. One way only, because of the nozzles: the slimmer petrol one slips inside a diesel filler with almost no resistance, whereas the diesel one generally won't fit a petrol motor. That is how the forecourt makes it easy.
Habit and your car getting out of step is when it occurs. Courtesy car, hire car, or a vehicle that is brand new. Two cars on one drive, one petrol, one diesel. Your usual forecourt, its pumps now in a different order. Racing for a train at Llangennech and filling up en route. The first fill-up in a diesel Volkswagen Golf after years of driving petrol is exactly the moment it occurs. Throw in a back seat full of children, a phone call or rain, and habit wins.
Next time you fill up in Penyrheol: avoiding petrol in a diesel
- The label is what matters, and so check the pump rather than the colour: in the UK unleaded handles are normally green and diesel black, yet not on every forecourt.
- In a vehicle you do not know, look inside the flap over the filler or at the cap before the first fill: plenty of motors state the fuel there.
- Good intentions do less than a sticker or a fob in a vivid colour on your diesel's key when a house has one of each. So label it.
- It seems daft and it works: on your first fill in a new or hired car, say "diesel" aloud before you take the nozzle off the petrol pump.
- Thinking about something else is when this becomes an easy mistake to make, so put your phone away then keep your mind on the pump.
- A misfuel inhibitor helps, up to a point. Some diesels come with a filler designed to reject a petrol nozzle, and add-on devices are available 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 the tank means a thinner blend. What to do next doesn't change, though — still don't fire it up.
Put petrol in a diesel in Penyrheol already?
Short and simple, then, is the order of things. Leave it unstarted, with your ignition switched off too. The attendants at the forecourt — whether at Asda itself or wherever you filled up — will normally help push it clear of the petrol pump if you ask. Next, 0333 366 0103. We will ask what went in, roughly how much, and if it has been run.
Corrosion and deposits form the problem with AdBlue, whereas petrol brings lost protection. So if it was AdBlue, say so — and see its own Penyrheol page.
One petrol in a diesel job in Penyrheol costs more than another. Why?
An honest single price doesn't exist here: four scenarios, four separate jobs. What moves your cost is mostly which of them you're in. Next it's the ratio — how much petrol went in against how much that tank holds — and then where your car is and whether our van can get to it safely.
Three questions come first, before quoting, instead of after — what was put in, how much, has it run — and this is the reason. A range becomes a straight figure once those replies are in.
About Penyrheol
Penyrheol is a suburban area located on the coast of Wales, approximately 6 miles from Swansea city centre. Penyrheol sits at an elevation of 61 metres, overlooking the surrounding landscape. Penyrheol is characterized by its predominantly semi-detached housing stock, reflecting the residential development of the area. Penyrheol is close to nearby places such as Gorseinon, Grovesend, and Loughor, and is situated within commuting distance of Swansea.
Across Swansea and around Penyrheol: fuel drain cover
Gorseinon, Grovesend and Loughor are among the places near Penyrheol that the same vans work, answering petrol in diesel jobs across Penyrheol's SA postcode area. A forecourt, a supermarket car park, a lay-by or your own driveway are all places our engineers work, and the car does not need to move to us.
Still at the petrol pump around Penyrheol?
Then, you could not be in a better place. Keep it off. Ring.