Petrol in a Diesel Car in Pipers Ash: How Worried Should You Be?
Not started? Then less anxious than you probably are. Petrol sitting in a diesel tank does nothing to your engine until something pulls it through the system — the ignition priming the pump, the starter, or driving itself. So the honest answer to the first query everyone around Pipers Ash asks, "have I ruined it?", is generally no. To keep the car that way, ring Petrol in Diesel and leave your engine alone. What petrol actually does to a diesel, how to gauge how far it has gone, and how to keep it from happening again: that's the remainder of this page.
Petrol in a diesel: what does it do to the motor?
On its way through an engine, diesel does two jobs. Lubricating comes before burning; it does both. Your high-pressure pump and your injectors are designed to very fine gaps, and the diesel passing through them is what stops those surfaces from wearing down against each other.
Petrol does the first job badly and the second not at all. Being less viscous than diesel, petrol strips away the protection a fuel system needs, so a pump on that mixture wearing itself. It is also made to resist igniting under compression — the reverse of what a diesel needs — which is why you get the clattering.
Taken together, they make clear the shape the trouble takes. Not contact but circulation is what does the damage. All a tank with petrol in it amounts to is a fuel issue. Whatever a worn pump sheds goes on, borne by your fuel, into the injectors further along, which is why a pump that has worked on the petrol is where a mechanical problem starts.
How serious is petrol in a diesel? Four scenarios our engineers see around Pipers Ash
Filled up, never started. The best case there can be. Only the tank has petrol in it, so the task is clearing that tank and rinsing the fuel system where the vehicle stands. This scenario can only really take place at a forecourt: anywhere else, the vehicle got there by being driven.
Ignition on, or started for a second. Once primed, your system has pulled petrol out of your tank up to the filter and the lines. Normally little more than emptying, cleaning and sorting your filter, and so still straightforward.
A couple of miles driven, and the pump has spent each of them working on weakened fuel. How hard the vehicle was driven counts as much as how far, and this work takes in the tank, your lines, the filter and clean fuel through the whole system. On the school run to Oldfield Primary School, the mileage is short. Getting as far as Chester, under 3 miles away, makes a very different task — as does any distance on the M53, under a mile from Pipers Ash, with the motor labouring hard the whole time.
It protested, and only then stopped: smoke, rattling, a throttle gone soft, an idle gone uneven. What you are hearing is the engine reporting fuel that no longer acts like diesel. Leave it where it stops: a lay-by, a quiet street, the verge on Belle Vue Lane. The fuel drain and flush-through still come first, and they sort it out: if a car is stopped early, permanent damage is very uncommon.
What Pipers Ash motorists get told about petrol in a diesel — and the myths in it
Myth: "Fill it the rest of the way with diesel and it will be fine." It will not. Nothing is removed when you top up — your tank simply carries more of the same mixture. The idea behind that advice — that diesel fuel systems tolerate petrol by percentage — is wrong.
Not so: a newer diesel copes with a bit of petrol. If anything, the opposite. Finer components and higher pressure are how a modern diesel runs its fuel, and that makes the lubrication matter more, not less.
Myth: "If it starts and drives, there's no damage done." This is the one that catches drivers. Feed diesel to a petrol motor and it normally won't run, so the motorist stops — and the harm stops with them. Nothing looks to have happened when a diesel fed petrol fires up, ticks over and drives away, as it usually does; meanwhile the pump grinds. Fine and running are not the same thing.
Not so: a two-stroke additive lets you to drive home. It is an old fix, supposed for another issue. The petrol is still inside the tank after that, and whatever it has weakened is not put back.
Myth: "Drain that tank yourself and you're sorted." Once the engine has run, some of that petrol is no longer in your tank: it is in your filter and your lines, and it goes right back through the pump on the next start. Also, a can of petrol filled at the roadside is truly hazardous.
How does petrol in a diesel occur?
A careless moment is seldom the cause, and nobody means to do it. The petrol nozzle is the smaller of the two and slips into a diesel filler with almost no resistance; a diesel nozzle mostly will not go into a petrol car at all. The forecourt makes it simple, and the error runs one way.
It happens when habit and your car stop matching. Courtesy car, hire car, or a vehicle that's new. One petrol and one diesel on the drive of the same household. The pumps in a different order on a familiar forecourt. Fuelling up in a rush on the way to Chester, with a train to catch. Years of petrol motors behind you, a diesel Volkswagen Golf in front of you at the forecourt for its first tank — that's when. With rain, a call arriving, or a car full of children to deal with, the hand just does what it has always done.
Preventing petrol in a diesel next time you fill up in Pipers Ash
- Not every forecourt in the UK keeps to green for unleaded and black for diesel, even if most usually do. Check the petrol pump's label; the colour is only a clue.
- In a car you don't know, look inside the flap over your filler or at the cap before the first fill: many cars print the fuel there.
- One of each in the home? Label your key to your diesel — a bright fob, a sticker — since meaning to remember isn't enough.
- It seems silly and it does the trick: on the first fill in a new or hired car, say "diesel" out loud before you lift 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.
- A misfuel inhibitor helps, up to a point. Some diesels have a filler built to reject a petrol nozzle, and add-on devices are available for vehicles without one. They are a backstop, not a reason to stop reading the petrol pump.
- Less petrol makes a weaker blend, so stop the moment you notice — while remembering that the next stage is unchanged. It's still not to crank it.
Put petrol in a diesel in Pipers Ash already?
Short and simple, then, is the order of things. Do not start the car, and do not switch the ignition on. The attendants at the forecourt — whether at Shell itself or wherever you filled up — will normally help roll it away from the petrol pump if you ask. Then ring 0333 366 0103 and tell us what went in, about how much, and if it's run.
Say so if it was AdBlue instead of petrol: it's a separate issue, with its own page for Pipers Ash, because AdBlue brings corrosion and deposits instead of lost protection.
One petrol in a diesel task around Pipers Ash costs more than another. Why?
The four scenarios above are four separate tasks, so no single quote for this would be honest. Chiefly, your cost moves with which situation you are in. Where the car is counts too, and whether a technician can safely get to it, after the proportion of petrol to what that tank holds.
Before any quote, not after, come three questions: the fuel that was put in, the amount, and whether it has run. That is why. Those answers are what change a range into one firm number.
About Pipers Ash and its setting
Pipers Ash is a small village in Cheshire, situated near the city of Chester and surrounded by other local communities such as Littleton and Vicarscross. Pipers Ash lies at an elevation of 41 metres, in a relatively low-lying area of the North West region. Pipers Ash has a population of around 572 people, predominantly living in semi-detached housing. Pipers Ash is located approximately 2 miles from Chester, making it a commuter-friendly location.
Across Cheshire and around Pipers Ash: fuel drain cover
Pipers Ash sits in the CH postcode area, and the teams that answer petrol in diesel jobs there work the places around it as well — Littleton, Vicarscross and Hoole among them. A forecourt, a supermarket car park, a lay-by or your own driveway are all places we work, and the vehicle doesn't need to come to us.
Still at the petrol pump in Pipers Ash?
No position is better: that's where you now are. Leave it switched off, then ring.