Bentley: Petrol in a Diesel Car? How Worried to Be
If it hasn't been started, worry less than you probably are. Until the ignition primes your pump, your starter turns, or the car is driven, petrol in a diesel tank just sits there and does nothing. Which makes the honest reply to that first Bentley question — "have I ruined it?" — usually no. To leave the vehicle that way, ring Petrol in Diesel then leave the motor switched off. What petrol really does to a diesel, how to gauge how far it has gone, and how to stop it from happening again: that's the remainder of this page.
Inside the motor: what petrol in a diesel really does
Passing through an engine, diesel does two jobs at once. Before it ignites, it lubricates — and then it burns. What keeps the surfaces inside the high-pressure pump and the fuel injectors from wearing down against one another is the diesel passing through them — they are made to very fine gaps.
Poorly at the first, not at all at the second: that is petrol. A pump working on a petrol blend is wearing itself out, because petrol is runnier than diesel and takes away the lubrication your fuel system depends on. Petrol is also made to resist igniting under compression — the reverse of what a diesel wants from its fuel — and that's where any clattering starts.
The shape of the problem is plain when you put those together. The damage is done by movement, not by contact. Petrol in the tank is a fuel fault. A pump that has been labouring on that petrol is the start of a mechanical one, and whatever a worn pump sheds moves on with your fuel to your injectors downstream.
Petrol in a diesel in Bentley: how bad is it? Four situations
Fuelled but not once started — the best it gets. The petrol is inside your tank and just that tank, and the task is a drain and a flush where the vehicle stands. This is the one scenario that can only truly take place at a forecourt, since anywhere else your car has been driven to get there.
Your ignition turned on, or a short start. The fuel system has been primed, and so petrol has left your tank and got to the filter and the fuel lines. Usually nothing more than draining, purging and seeing to the filter, so still easy.
A couple of miles driven, and your pump has spent each of them working on weakened fuel. How hard your car was driven counts as much as how far, and the work covers the tank, the fuel lines, the fuel filter and fresh fuel through the entire system. Short trips, like the school run to King Charles Primary School, are one matter. A run as far as Wolverhampton, under 5 miles away, is a very different task. So is any distance on the M6, under a mile from Bentley, where the engine has been working hard the whole time.
It protested, and only then stopped: smoke, rattling, a throttle gone soft, an idle gone uneven. The fuel is not acting like diesel any more, and the motor is telling you. Pull up wherever you are — the verge on Bader Road, a lay-by, a side street — and leave the car where it is. A car stopped early very rarely has permanent damage, because the drain and the flush-through, which still come first, deal with it.
Bentley drivers and that petrol in a diesel myths they hear
It will not be fine. The myth: "Fill it the rest of the way with diesel and it'll be." A fuller tank of the same mixture is all you get, since topping up removes nothing. That guidance assumes a diesel fuel system tolerates petrol by percentage. It does not.
Myth: "A newer diesel can cope with a bit of petrol." If anything, the opposite. At higher pressure, through smaller components: that's how a current diesel handles its fuel, and so the protection counts more, not less.
This is the one that catches people. Myth: "If it starts and drives, there is no damage done." A petrol motor fed diesel normally won't run, so the driver stops and the damage stops with them. Nothing looks to have happened when a diesel fed petrol fires up, ticks over and drives away, as it usually will; meanwhile your pump grinds. Running is not the same as fine.
Not so: a two-stroke additive lets you to drive home. It was an old fix, supposed for another fault. The petrol is still in the tank afterwards, and what it has weakened is not put back.
"Drain it yourself and you're sorted" — a myth, because after it has been running some petrol lies in the fuel filter and lines, waiting to go right back through the pump at the next start. On top of that, petrol cleared into a can by the road is truly hazardous.
Why petrol in a diesel takes place at all
A careless moment is rarely the cause, and nobody means to do it. The forecourt makes it simple: the petrol nozzle is the smaller of the two, and it slides into a diesel filler with almost no resistance, whilst a diesel nozzle mostly won't go into a petrol motor at all. So the slip runs one way.
When routine and the vehicle stop matching, it takes place. Courtesy car, hire car, or a motor that is brand new. A household with one petrol and one diesel on the drive. A well-known forecourt with the pumps in a different order. Filling up in a hurry on the way to Darlaston, with a train to catch. The first fill-up in a diesel Volkswagen Golf after years of driving petrol is exactly the moment it takes place. Your hand does what it has always done once you add rain, a phone call or a back seat full of children.
How to prevent petrol in a diesel at your next fill-up in Bentley
- Read the petrol pump, not the colour. In the UK unleaded handles are generally green and diesel black, but not on every forecourt. The label is what counts.
- The first fill in a strange vehicle is the time to check your filler flap — inside it, or on the cap, plenty of vehicles state the fuel they take.
- One of each in the home? Label the key to your diesel — a bright fob, a sticker — because intending to remember isn't enough.
- "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.
- Mistakes like this are simple to make while your mind is on something else, so the phone goes away.
- A misfuel inhibitor helps, up to a point. Some diesels come with a filler built to reject a petrol nozzle, and add-on devices exist for vehicles without one. They are a backstop, not a reason to stop reading the pump.
- Less petrol makes a weaker mixture, and so stop as soon as you realise — while remembering that the next step is unchanged. It is still not to fire it up.
Already put petrol in a diesel in Bentley?
Short and simple, then, is the order of things. Starting it is out, and so is switching on your ignition. If you are still on the forecourt — the nearest petrol station or anywhere else — ask the staff to help you push the vehicle away from the petrol pump. Next, 0333 366 0103. We'll ask what got in, roughly how much, and if it's been run.
If it was AdBlue instead of petrol, say so. That is a different issue — corrosion and deposits rather than lost protection — and it has its own page for Bentley.
What makes one Bentley petrol in a diesel task cost more than the next
An honest single quote does not exist here: four scenarios, four separate tasks. Chiefly, the cost moves with which situation you are in. Two things come after that: the petrol that went in as a share of what your tank takes, then the spot the vehicle is in and whether a technician can reach it safely.
Before any quote, not after, we ask three questions: your fuel that went in, its quantity, and whether it's run. That's why. A range becomes a straight figure once the replies are in.
About Bentley, briefly
Bentley is a suburban area in the West Midlands, situated near the River Tame and close to the city of Wolverhampton. Bentley has a mix of housing types, but semi-detached homes are the most common, and its population is around 5751 residents. Bentley is located near several other local areas, including County Bridge, Shepwell Green, and The Flatts, and is about 4.5 miles from Wolverhampton city centre. Bentley sits at an elevation of 145 metres above sea level, in a riverside setting that provides scenic views and outdoor recreational opportunities.
Bentley and West Midlands: where our fuel drain cover reaches
Bentley sits in the WS postcode area, and the teams that answer petrol in diesel calls there work the locations near it as well — County Bridge, Shepwell Green and The Flatts among them. Our technicians drain wherever the car is — your own driveway, a lay-by, a supermarket car park, a forecourt — so it does not have to come to us.
Still at the pump around Bentley?
Nothing beats it: that's where you are. Leave it turned off, and ring.