Whittle Brook: Petrol in a Diesel Car? How Worried to Be
Unstarted? Then less anxious than you probably feel. Until your ignition primes the pump, the starter cranks, or the car is driven, petrol in a diesel tank simply rests there and does nothing. Which means the honest reply to that first Whittle Brook query — "have I ruined it?" — normally no. To keep it that way, ring Petrol in Diesel then leave the motor switched off. Keep reading for three things: the effect petrol has inside a diesel motor, the signs of how far it has got, and the way to make sure you don't do it again.
Your engine and petrol in a diesel: what goes on
Passing through an engine, diesel is doing two jobs at once. Before it combusts, it lubricates — then it combusts. What stops the surfaces inside the high-pressure fuel pump and the injectors from wearing against each other is your diesel flowing through them — they are designed to very fine clearances.
Of these two jobs, petrol manages the first badly and the second not at all. Being less viscous than diesel, petrol strips away the lubrication a fuel system needs, so a pump running on the mixture wearing itself. It's equally made to resist igniting under compression — the reverse of what a diesel needs — which is where you get the clattering.
Put those together and the shape of the issue is plain. It is movement that does the damage, not contact. A tank with petrol in it is a fuel problem. A pump that has been running 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 Whittle Brook: how bad is it? Four cases
Filled but not once started — as good as it gets. On a forecourt, and genuinely only there, the petrol is still limited to the tank — because anywhere else the vehicle was driven to get to it. The job is draining and cleaning on the spot.
A moment's running, or merely your ignition on. Once primed, your system has pulled petrol out of your tank up to the filter and the lines. Usually nothing more than emptying, flushing and seeing to the fuel filter, and so still simple.
Driven a few miles. Now your pump has spent those miles working on diluted fuel. Tank, lines, filter, then clean fuel run through the whole circuit: that's the work, and the way the vehicle was driven counts as much as the distance. On the school run to St Paul's CofE Primary School, the mileage is small. Very different again: a run to Salford, under 5 miles away, or some miles on the M61, under a mile from Whittle Brook, where the motor kept running hard.
It complained, and only then stopped: smoke, knocking, a throttle gone soft, an idle gone uneven. That is the engine telling you its fuel no longer is acting like diesel. Leave it wherever it stops: a lay-by, a side street, the verge on Grundy Street. What comes first is still the drain and flush-through, and that deals with it, with permanent damage very uncommon if a vehicle is pulled over quickly.
Stories Whittle Brook people hear about petrol in a diesel
Myth: "Fill it the rest of the way with diesel and it will be fine." It will not. Topping up takes out nothing; it gives you a fuller tank of the same mixture. Percentage is not how a diesel fuel system tolerates petrol, whatever that advice presumes.
Myth: a current diesel copes with a bit of petrol. If anything, the opposite. A modern diesel sends its fuel through smaller parts at higher pressure, which makes the lubrication count more, not less.
The myth that catches drivers out: if it starts and drives, it must be unharmed. A petrol engine fed diesel usually won't run, and so the driver stops and the harm stops with them. Whilst your pump grinds, a diesel fed petrol usually starts, ticks over and drives away as if nothing has happened. Running is not the same as fine.
"A drop of two-stroke oil and drive it home" — a myth, taken from a fix from years ago, for a different problem. The petrol is still inside the tank after that, and what it has thinned isn't put back.
"Drain it yourself and you're sorted" — a myth, since after it's been running some petrol lies in the filter and lines, waiting to go right back through the pump at your next start. Draining petrol into a can by the roadside is also truly dangerous.
How does petrol in a diesel occur?
On purpose? Never. Through carelessness? Rarely, if ever. The forecourt makes it easy: the petrol nozzle is the narrower of the two, and it slides into a diesel filler with almost no resistance, whilst a diesel nozzle generally won't go into a petrol vehicle at all. So the error runs one way.
The moment routine stops matching your car is the moment it takes place. Any vehicle that's new to you — hired, on loan as a courtesy car, or brand new. Households running one of each, petrol and diesel. The pumps in a different order on a familiar forecourt. A rushed fill en route to Walkden with a train to catch. A new-to-you diesel Volkswagen Golf, its first fuelling, and a driver accustomed to petrol: precisely when it occurs. With rain, a call coming in, or children to deal with, the hand just does what it has always done.
How to prevent petrol in a diesel at your next fill-up in Whittle Brook
- The label is what matters, so check the petrol pump instead of the colour: in the UK unleaded handles are usually green and diesel black, yet not on each forecourt.
- In a motor you don't know, look inside the flap over your filler or at the cap before the first fill: plenty of motors state the fuel there.
- A coloured fob or a sticker on the diesel's key achieves more than any amount of meaning to remember, for a house with one of each.
- Say it before you lift it. On your first fill in a new or hired car, say "diesel" aloud before you take the nozzle off the petrol pump. It sounds daft and it does the trick.
- Mistakes like this are straightforward to make while your mind is on something else, so your phone goes away.
- Up to a point, a misfuel inhibitor helps: some diesels come with a filler built to block a petrol nozzle, and aftermarket devices are available for the rest. Treat it as a backstop, then keep reading the pump.
- Less petrol makes a weaker mix, so stop the moment you realise — while remembering that the next stage is unchanged. It is still not to start it.
Put petrol in a diesel in Whittle Brook already?
Then the order of things is short. Starting it is out, and so is switching on your ignition. Ask the attendants to help you push it away from the petrol pump if you are still on the forecourt, whether that is Texaco or anywhere else. Then ring 0333 366 0103 and tell us what went in, about how much, and if it has run.
Corrosion and deposits form the problem with AdBlue, where petrol means lost lubrication. So if it was AdBlue, say so — and read its own Whittle Brook page.
One petrol in a diesel job in Whittle Brook costs more than another. Why?
Four different tasks lie behind the four situations above — which is why there's no fair single price. What shifts the cost is mostly which of them you're in. Two things come after that: the petrol that went in as a share of what the tank takes, then the spot the vehicle is in and whether a van can reach it safely.
Ahead of any quote, not after, come three questions: the fuel that was put in, the amount, and whether it has run. That is why. The answers turn a range into a straight figure.
About Whittle Brook
Whittle Brook is a suburban area in Greater Manchester, situated near the lakeside and approximately 87 metres above sea level. Whittle Brook lies close to the city of Salford, about 4.7 miles away, and is near other local places such as Linnyshaw, Walkden, and Roe Green. Whittle Brook has a population of around 7138 people and is characterised by its predominant semi-detached housing stock.
Across Greater Manchester and in Whittle Brook: fuel drain cover
Whittle Brook rests in the M postcode area, and the vans that answer petrol in diesel jobs there work the places around it as well — Linnyshaw, Walkden and Roe Green among them. The car doesn't need to come to us: our engineers drain at a forecourt, in a supermarket car park, in a lay-by or on your own drive.
Still at the petrol pump in Whittle Brook?
No position is better: that is where you now are. Keep the vehicle turned off, then ring.