How Worried Should You Be? Petrol in a Diesel Car in The Woods
Provided it has not been started, worry less than you likely are. Until the ignition primes the pump, the starter turns, or your car is driven, petrol in a diesel tank just sits there and does nothing. Which means the honest reply to that first The Woods query — "have I wrecked it?" — normally no. To leave the vehicle like that, ring Petrol in Diesel and leave the motor alone. Below, you will find what petrol really does inside a diesel, how far it may have gone, and how to stop it happening to you again.
Petrol in a diesel: what does it do to the motor?
Diesel has two tasks on its way through a motor. It burns, and before it ignites it lubricates. Extremely fine clearances are built into the fuel injectors and the high-pressure fuel pump, and just the diesel running through stops those surfaces grinding together.
The second job petrol does not do at all, and the first it does poorly. 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 needs from its fuel — and that's where the knocking comes.
The shape of the problem is clear once you put those together. The harm is done by movement, not by contact. All a tank with petrol in it amounts to is a fuel problem. A pump that has been labouring on that petrol is the beginning of a mechanical one, and whatever a worn pump sheds moves on with your fuel to the injectors further on.
The Woods, petrol in a diesel: four situations, from mild to serious
Fuelled but not once started — the best it gets. On a forecourt, and genuinely only there, that petrol is still limited to the tank — because anywhere else your car was driven to get to it. The task is emptying and flushing on the spot.
A brief spell of running, or just your ignition on. Petrol has left the tank and reached your filter and your lines, because your system has been primed. That is generally still an easy task — a drain, a flush, and your filter seen to.
Driven a few miles. Now the pump has spent those miles working on thinned fuel. Tank, lines, filter, then clean fuel run through the whole circuit: that's this work, and the way the vehicle was driven matters as much as the distance. Short trips, like the school run to Park Hill Primary School, are one thing. A run as far as Wolverhampton, under 10 miles away, is a very different task. So is any distance on the M6, under a mile from The Woods, where the engine has been running hard the whole time.
Driven on till it complained — rattling, smoke, a ragged idle, a soft throttle. The motor is telling you your fuel is no longer behaving like diesel. Whether it is the verge on Woden Road East, a lay-by or a side street, stop there then leave it. A car stopped soon very rarely has long-term damage, since the drain and the flush, which still come first, sort it out.
What The Woods motorists get told about petrol in a diesel — and the myths in it
False: topping up to full with diesel makes it fine. It doesn't. Topping up removes nothing; it gives you a bigger tank of the same mix. The assumption behind that advice — that diesel fuel systems tolerate petrol by percentage — is wrong.
Myth: "A modern diesel can cope with a bit of petrol." If anything, the opposite. Protection matters more on current diesels, not less, since their fuel runs through finer parts at higher pressure.
This is the one that fools drivers. Myth: "If it starts and drives, there's no damage done." The motorist of a petrol engine fed diesel normally has no choice but to stop, because it will not run, and the harm stops with them. A diesel fed petrol generally starts, ticks over and drives away as if nothing has happened, whilst your pump wears. Fine and running are not the same thing.
Myth: "Add some two-stroke oil and drive the car home." It is an old fix for a separate problem. The petrol is still inside that tank after that, and what it has thinned isn't put back.
"Drain it yourself and you are sorted" — a myth, because after it's been running some petrol sits in your filter and lines, waiting to go straight back through your pump on your next start. Also, a can of petrol filled by the kerbside is genuinely dangerous.
How it happens: petrol in a diesel
A careless moment is rarely the cause, and nobody means to do it. The petrol nozzle is the smaller of the two and slides into a diesel filler with almost no resistance; a diesel nozzle generally will not go into a petrol vehicle at all. The forecourt makes it simple, and the mistake runs one way.
The moment routine stops matching the car is the moment it takes place. A new vehicle, a hire car or a courtesy car. Households running one of each, petrol and diesel. A forecourt you know, but with its pumps arranged differently. Fuelling up in a hurry on the way to Bescot Stadium, with a train to catch. Years of petrol cars behind you, a diesel Volkswagen Golf in front of you at the forecourt for its first tank — that's when. Your hand does what it has always done when you add rain, a phone call or a back seat full of children.
Preventing petrol in a diesel next time you fill up around The Woods
- Green for unleaded and black for diesel is normal in the UK — but not on each forecourt. Go by the label on the pump, not the colour.
- In a motor you don't know, look inside the flap over your filler or at the cap before your first fill: plenty of cars state the fuel type there.
- One of each in the home? Label the key to your diesel — a bright fob, a sticker — since intending to remember is not enough.
- Before the nozzle leaves the petrol pump the first time you fuel a hired or new car, say "diesel" out loud. Silly, yes, but it works.
- Put your phone away. This is an easy mistake to make whilst you are thinking about something else.
- Add-on devices are available for cars without one, and some diesels are built with a filler that won't take a petrol nozzle. Useful — but a backstop at best, never a reason to stop checking the label.
- Less petrol makes a thinner mixture, so stop the moment you realise — while remembering that your next step is unchanged. It is still not to start it.
Already put petrol in a diesel around The Woods?
The order of things is brief, then. Leave it unstarted, with your ignition off as well. Yet on the forecourt, at Esso or anywhere else? Ask the staff to help you push the vehicle clear of the pump. What got in, roughly how much, and whether it has run: tell us those when you phone 0333 366 0103.
If it was AdBlue rather than petrol, say so. That is a different problem — corrosion and deposits rather than lost lubrication — and it has its own page for The Woods.
What makes one The Woods petrol in a diesel task cost more than the next
The four scenarios above are four different tasks, so no single quote for this would be fair. Chiefly, your cost shifts with which one you're in. Two things follow that: the petrol that got in as a share of what that tank holds, then the place your car is in and whether a technician can get to it safely.
Ahead of any quote, not after, we ask three questions: the fuel that got in, its quantity, and whether it's run. That is why. The replies change a range into a straight figure.
About The Woods and its setting
The Woods is a suburban area located on the riverside in the West Midlands, with an elevation of 117 metres. The Woods sits near the city of Wolverhampton, approximately 5.7 miles away, and is close to nearby places such as Wood Green and Vicarage. The Woods is characterised by its predominant semi-detached housing stock, typical of many suburban areas in the region. The Woods is situated about 107.8 miles northwest of London, making it a commuter hub for those working in the capital.
Across West Midlands and in The Woods: fuel drain cover
The teams answering petrol in diesel calls in The Woods, in the WS postcode area, also work the places around it, Wood Green, Vicarage and Bescot among them. We drain wherever the vehicle is — your own driveway, a lay-by, a supermarket car park, a forecourt — so it never needs to come to us.
In The Woods and still at the petrol pump?
Nothing beats it: that's where you are. Phone, and keep it turned off.