Burren: Petrol in a Diesel Car? How Worried to Be
If it has not been started, you can worry far less than you likely are. "Have I ruined it?" is the first thing anyone around Burren asks, and the truthful answer is normally no, because petrol resting in a diesel tank harms nothing until it is dragged through the system — by ignition priming, by your starter, or by being driven. Leave the motor off and call Petrol in Diesel — that keeps it like that. Below, you will find what petrol really does inside a diesel, how far it might have got, and how to stop it happening to you a second time.
Petrol in a diesel: what does it do to the engine?
Diesel does two jobs on its way through an engine. Lubricating comes before burning; it does both. What stops the surfaces inside your high-pressure pump and the fuel injectors from wearing down against one another is your diesel passing through them — they're built to extremely fine clearances.
Poorly at the first, not at all at the second: that's petrol. The rattling comes from petrol being designed not to ignite when compressed, which is exactly the reverse of what a diesel needs. On top of that it is thinner than diesel, it strips out the lubrication your system hinges on, and any pump running on such a mixture is wearing itself.
Combined, those make the shape of the problem clear. Contact does not do the harm — movement does. All a tank with petrol in it amounts to is a fuel problem. Whatever a worn pump sheds goes on, carried by your fuel, into the fuel injectors further along, which is why a pump that has worked on the petrol is where a mechanical problem begins.
Burren, petrol in a diesel: four situations, from mild to major
The best case there can be: 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's emptied and cleaned right where it stands, and nothing more is needed.
A brief spell of running, or just your ignition on. Once primed, the system has drawn petrol from that tank up to the fuel filter and your lines. Usually little more than draining, flushing and seeing to the filter, and so still straightforward.
Driven a couple of miles. Now your pump has spent those miles labouring on weakened fuel. Miles is only half of it; how hard it was driven counts equally. Either way this work runs to the tank, the lines, the filter and fresh fuel through the entire circuit. Short trips, such as the school run to the local primary school, are one thing. Very different again: a run to Newry, under 5 miles away, or some miles on the M77, over 50 miles from Burren, where the motor never stopped running hard.
Driven on till it complained — knocking, smoke, a ragged idle, a dead throttle. The fuel is not acting like diesel any more, and the motor is telling you. Stop where you are — on the verge on B7041, at the kerb, down a side road — and don't move it again. Permanent damage is very rare if a vehicle is stopped quickly, and the fuel drain and flush-through that still come first deal with it.
Burren drivers and the petrol in a diesel stories they hear
False: topping up to full with diesel makes it fine. It does not. Nothing comes out when you top up — that tank just holds more of the same blend. A diesel fuel system does not accept petrol by percentage in the way that advice supposes.
"Current diesels can handle a little petrol" — a myth, and closer to the opposite. At higher pressure, through more precise parts: that's how a current diesel handles its fuel, and so the protection matters for more, not less.
Myth: "If it starts and drives, there's no damage done." This is the one that fools people. The driver of a petrol motor fed diesel usually stops, because it will not run, and the harm stops there. A diesel fed petrol normally starts, idles and drives away as if nothing has happened, whilst the pump wears. Being able to run is not proof of being fine.
Myth: "Add some two-stroke oil and drive the vehicle home." It's an old fix for a distinct issue. That petrol is still inside your tank afterwards, and what it has thinned is not put back.
Myth: "Drain the tank yourself and you're sorted." Once the engine has been run, some of that petrol is no longer in your tank: it is in your filter and your lines, and it goes straight back through the pump at the next start. Besides, petrol drained into a can by the road is truly hazardous.
How does petrol in a diesel take place?
Nobody does it on purpose, and it's rarely carelessness. A diesel nozzle mostly will not go into a petrol car, yet the narrower petrol nozzle goes into the filler of a diesel almost without resistance — so forecourts make this one mistake straightforward, and only in that direction.
It occurs when habit and the vehicle stop matching. Hire cars, courtesy cars, and cars that are new to you. Two vehicles on one drive, one petrol, one diesel. The pumps in a different order on a familiar forecourt. Racing for a train outside the nearest station and fuelling up en route. A new-to-you diesel Volkswagen Golf, its first fuelling, and a motorist used to petrol: precisely when it occurs. Throw in rain, a phone call or a back seat full of children, and the hand repeats what it has always done.
Preventing petrol in a diesel next time you fill up in Burren
- Not every forecourt in the UK keeps to green for unleaded and black for diesel, though most generally do. Read the pump's label; the colour is just a hint.
- The first fill in a new vehicle is the time to check the filler flap — inside it, or on the cap, many cars state which fuel to use.
- Label your key. In a house with one of each, a coloured fob or a sticker on your diesel's key does more than any amount of intending to remember.
- Say it before you lift it. On the first fill in a new or hired car, say "diesel" out loud before you take the nozzle off the petrol pump. It sounds daft and it works.
- Thinking about something else is when this becomes an easy mistake to make, so tuck the 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 block a petrol nozzle, and add-on devices are available for cars without one. They are a safety net, not a reason to stop reading the petrol pump.
- As soon as you realise, stop: less petrol in your tank means a thinner mixture. What to do next doesn't change, though — still don't fire it up.
Burren: already put petrol in a diesel?
The order of things is brief, then. Don't switch your ignition on, and don't crank it. Yet on the forecourt, at the nearest petrol station or anywhere else? Ask the staff to help you roll it clear of the pump. Next, 0333 366 0103. We will ask what was put in, roughly how much, and if it's been run.
Say so if it was AdBlue rather than petrol: it's a separate issue, with its own page for Burren, since AdBlue brings corrosion and deposits rather than lost protection.
What makes one Burren petrol in a diesel job cost more than the next
Four separate tasks sit behind the four scenarios above — which is why there is no fair single price. Chiefly, the cost shifts with which one you are in. The proportion counts next, meaning how much of that tank is petrol, and then the location of the vehicle and whether getting to it is safe for a technician.
What got in, how much, and if it's run — three questions our engineers ask before pricing, not after, for exactly that reason. Given the replies, there is a straight figure rather than a range.
About Burren
Burren is a small coastal locality in County Down, situated near the cities of Newry and Warrenpoint. Burren sits at an elevation of 107 metres, overlooking the surrounding countryside and coastline. Burren is characterised by its predominantly detached housing stock, reflecting its residential nature. Burren is located approximately 4.6 miles from Newry, making it a commuter base for the city.
Across County Down and in Burren: fuel drain cover
Burren rests in the BT postcode area, and our teams that answer petrol in diesel jobs there work the locations near it as well — Warrenpoint, Killeen and Rostrevor among them. You need not bring the car to us. Forecourts, supermarket car parks, lay-bys and your own drive are all places where we work.
At the petrol pump in Burren, right now?
In that case, you couldn't be in a better spot. Phone, and keep it turned off.