Petrol in a Diesel Car in Hunters Yard: How Worried Should You Be?
If it hasn't been started, worry less than you likely are. Everyone around Hunters Yard starts with "have I wrecked it?", and the fair answer is normally no: petrol resting in your tank of a diesel remains harmless until priming, cranking or driving draws it into the system. Petrol in Diesel is who to ring, with the motor left off, and so it stays that way. The remainder of this page sets out what petrol really does to a diesel, how to judge how far it has got, and how to make sure it does not happen to you again.
What petrol in a diesel does to the engine
On its way through a motor, diesel has two tasks. It lubricates first, and after that does it burn. Designed to very fine clearances, the fuel injectors and your pump rely on the diesel flowing through them to stop their surfaces wearing against one another.
Of those two jobs, petrol handles the first poorly and the second not at all. Being less viscous than diesel, petrol strips away the lubrication a fuel system needs, leaving a pump running on the blend to wear itself. It's also made to resist igniting under compression — the opposite of what a diesel needs — which is why you get the knocking.
Seen together, they make clear the shape the trouble has. The harm is done by movement, not by contact. Any tank with petrol in it is a fuel problem. The beginning of a mechanical one is a pump that has been running on that petrol — and whatever a worn pump sheds travels on with your fuel to your injectors downstream.
Petrol in a diesel around Hunters Yard: how bad is it? Four situations
The best case there can be: filled up, never started. Being on a forecourt is what makes this possible: elsewhere, your car has been driven there to begin with. With that petrol held in your tank alone, it is drained and purged on the spot, and nothing more is needed.
A brief spell of running, or just your ignition on. Petrol has come out of that tank and got to your filter and the lines, because the system has been bled. Still usually simple: drain, flush, and the filter sorted.
A couple of miles driven, and the pump has spent every one of them working on diluted fuel. Tank, lines, filter, then fresh fuel put through the whole system: that is the work, and the way the vehicle was driven counts as much as the mileage. Short trips, such as the school run to Whitchurch Combined School, are one thing. Very different once more: a trip to Milton Keynes, under 15 miles away, or some miles on the M40, under 15 miles from Hunters Yard, where the motor kept working hard.
It complained, and only then stopped: smoke, clattering, a throttle gone soft, an idle gone uneven. What you are hearing is your engine reporting fuel that no longer acts like diesel. Leave it wherever it has stopped: a lay-by, a quiet street, the verge on Ashgrove Gardens. The fuel drain and flush-through still go first, and they sort it out: if a vehicle is stopped soon, lasting damage is very rare.
Myths Hunters Yard people hear about petrol in a diesel
It will not be fine. The myth: "Fill it the rest of the way with diesel and it will be." Topping up takes out nothing; it gives you a fuller tank of the same mixture. Percentage isn't how a diesel fuel system tolerates petrol, however much that guidance supposes.
If anything, the opposite holds. Myth: "A current diesel can cope with a bit of petrol." At higher pressure, through more precise parts: that's how a newer diesel handles its fuel, so the lubrication counts for more, not less.
Myth: "If it starts and drives, there is no damage done." This is the one that catches drivers. A petrol engine fed diesel usually will not run, and so the motorist stops and the harm stops with them. While the pump wears, a diesel fed petrol normally starts, idles and drives away as if nothing has happened. Fine and running are not the same thing.
Not so: a two-stroke additive makes it safe to drive home. It was an old fix, meant for another fault. That petrol is still inside your tank after that, and what it has diluted is not put back.
Once your engine has run, part of the petrol is in your 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" doesn't hold. Also, a can of petrol drained at the kerbside is truly hazardous.
Why petrol in a diesel occurs at all
It is seldom carelessness, and no one does it on purpose. A diesel nozzle mostly won't fit a petrol motor, but the smaller petrol nozzle goes into the filler of a diesel nearly without resistance — so forecourts make this one error simple, and just in that direction.
The moment habit stops matching your car is the moment it takes place. Hire cars, courtesy cars, and motors that are new to you. Households running one of each, petrol and diesel. A well-known forecourt with the pumps in a different order. A rushed fill on the way to Aylesbury Vale Parkway with a train to catch. The first fill-up in a diesel Volkswagen Golf after years of driving petrol is precisely the moment it occurs. Add rain, a phone call or a back seat full of children, and the hand does what it has always done.
Next time you fill up around Hunters Yard: avoiding petrol in a diesel
- Not every forecourt in the UK follows green for unleaded and black for diesel, even if most generally do. Check the petrol pump's label; the colour is only a hint.
- Check the filler flap. Plenty of motors state the fuel inside the flap or on the cap. Look at it on your first fill in a motor you don't know.
- A coloured fob or a sticker on your diesel's key does more than any amount of intending to remember, for a house with one of each.
- "Diesel", aloud, before you lift the nozzle — each time a new or hired car needs its first tank. It seems daft. It does the trick.
- Thinking about something else is when this becomes an easy mistake to make, so put the phone away and keep your mind on the petrol pump.
- Up to a point, a misfuel inhibitor helps: some diesels have a filler built to refuse a petrol nozzle, and aftermarket devices are available for the rest. Count it as a backstop, and keep reading the petrol pump.
- Stop as soon as you realise. Less petrol in the tank means a thinner blend. It does not change what to do next, which is still not to fire it up.
Petrol already in a diesel in Hunters Yard? Start here
Then the order of things is brief. Leave it unstarted, with your ignition off as well. If you are still on the forecourt — Gulf or anywhere else — ask the attendants to help you roll the vehicle clear of the petrol pump. Next, 0333 366 0103. We'll ask what was put in, roughly how much, and if it's been run.
AdBlue, not petrol? Then tell us. Corrosion and deposits, not lost protection, make it a different issue — Hunters Yard has a page all for it.
One petrol in a diesel job around Hunters Yard costs more than another. Why?
The four situations above are four different tasks, so no single quote for this would be fair. What moves the cost is chiefly which of them you're in. Next it is the share — how much petrol went in against how much your tank takes — and after that where the car is and whether a van can get to it safely.
Three questions come first, before any quote, rather than after — what went in, how much, has it run — and this is the reason. A range becomes a straight figure when the answers are in.
About Hunters Yard itself
Hunters Yard is a locality in inland Buckinghamshire, situated approximately 40 miles northwest of London and 12 miles southeast of Milton Keynes. Hunters Yard has a population of around 632 people and is characterised by semi-detached housing. Hunters Yard is close to nearby places such as Whitchurch, Oving, and Creslow, and sits at an elevation of 139 metres.
Fuel drain cover across Buckinghamshire, Hunters Yard included
Petrol in diesel jobs around Hunters Yard — part of the HP postcode area — go to vans that likewise cover the spots round it, Whitchurch, Oving and Creslow included. Our engineers drain wherever your car is — your own drive, a lay-by, a supermarket car park, a forecourt — so it never needs to come to us.
Hunters Yard: still at the petrol pump?
The best position there is, then — that's where you are. Turned off it stays; then call.