Should You Worry? Petrol in a Diesel Car in Smallwood
If it has not been started, worry less than you probably are. "Have I ruined it?" is the first question anyone around Smallwood asks, and the truthful answer is normally no, since petrol left in a diesel tank hurts nothing until it is drawn through the fuel system — by ignition priming, by the starter, or by driving. To keep the vehicle like that, phone Petrol in Diesel and leave your motor alone. The rest of this page sets out what petrol actually 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
Diesel has two tasks on its way through a motor. It lubricates first, and only then does it burn. Made to very fine gaps, the fuel injectors and the pump rely on your diesel moving through them to stop their surfaces wearing against one another.
The second job petrol doesn't do at all, and the first it does badly. It is thinner than diesel and takes away the protection the fuel system hinges on, so a pump running on a petrol blend is a pump wearing itself. And petrol is made to resist igniting under compression, which is the reverse of what a diesel needs from its fuel. That is where the knocking comes from.
The shape of the problem is clear when you put those together. Contact does not do the harm — movement does. Petrol in a tank is a fuel fault. The start of a mechanical problem is a pump that has been labouring on that petrol — and whatever a worn pump sheds travels on with your fuel to the injectors beyond it.
How serious is petrol in a diesel? Four scenarios our engineers see in Smallwood
Fuelled but not once started — the best it gets. Only the tank has petrol in it, and so the job is emptying the tank and rinsing your system where your car stands. This scenario can only really occur on a forecourt: anywhere else, your car got there by being driven.
Started for a moment, or just your ignition on. Petrol has come out of your tank and got to the filter and the fuel lines, since your system has been bled. That is normally still an easy job — a drain, a flush, and your filter seen to.
Some miles driven, and your pump has spent each of them labouring on weakened fuel. How hard your car was driven matters as much as how far, and the work takes in that tank, the fuel lines, the fuel filter and fresh fuel through the entire system. The school run to St George's CofE First School and Nursery is one thing. Any miles on the M42, under 5 miles from Smallwood, means the motor has worked hard throughout, and a run to Birmingham, under 15 miles away, is a very different task too.
Clattering, a lumpy idle, smoke, a throttle gone soft: driven till it complained. What you are hearing is your motor signalling fuel that no longer behaves like diesel. Stop where you are — on the verge on Lodge Road, at the kerb, down a side road — and do not move it. The drain and flush still go first, and they sort it out: if a car is pulled over early, lasting damage is very uncommon.
Myths Smallwood drivers hear about petrol in a diesel
Myth: "Fill it the rest of the way with diesel and it will be fine." It will not. A fuller tank of the same mix is all it gives, since topping up takes out nothing. A diesel fuel system doesn't accept petrol by percentage in the way that guidance presumes.
Myth: "A modern diesel can cope with a bit of petrol." If anything, the opposite. More precise parts and higher pressure are the way a modern diesel runs its fuel, and that makes the lubrication matter more, not less.
This is the one that fools drivers. Myth: "If it starts and drives, there's no damage done." Diesel in a petrol motor normally leaves a motor that will not run: the motorist stops, and so does the harm. While the pump grinds, a diesel fed petrol usually starts, idles and drives away as though nothing has happened. Fine and running are not the same thing.
Myth: a two-stroke additive lets you to drive home. It was an old workaround, meant for another problem. It does not put back what petrol has diluted, and that petrol is still in your tank later.
Myth: "Drain your tank yourself and you are sorted." Once the motor has run, some of the petrol is no longer in that tank: it's in the filter and your lines, and it goes right back through the pump on your next start. And, a can of petrol drained by the kerbside is truly dangerous.
Why petrol in a diesel takes place at all
Carelessness is seldom the cause, and no one 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 vehicle at all. The forecourt makes it simple, and the error runs one way.
The moment habit stops matching the car is the moment it occurs. Any vehicle that is new to you — hired, on loan as a courtesy car, or just bought. Households running one of each, petrol and diesel. A well-known forecourt with the pumps in a different order. Racing for a train outside Redditch and filling up en route. Exactly the moment it takes place: after years of driving petrol, a driver fills a diesel Skoda Octavia for the first time. The hand repeats what it has always done when you add rain, a phone call or a back seat full of kids.
How to prevent petrol in a diesel at your next fill-up in Smallwood
- Not every forecourt in the UK follows green for unleaded and black for diesel, though most usually do. Check the petrol pump's label; the colour is just a hint.
- Check your filler flap. Plenty of vehicles state the fuel type inside the flap or on the cap. Look at it on your first fill in a car you don't know.
- One of each in the home? Mark your key to the diesel — a bright fob, a sticker — since intending to remember isn't enough.
- It seems silly and it does the trick: on your first fill in a new or hired car, say "diesel" aloud before you take the nozzle off the petrol pump.
- While you are thinking about something else, this is an easy mistake to make — so put the phone away.
- Up to a point, a misfuel inhibitor helps: some diesels come with a filler built to reject a petrol nozzle, and add-on devices are available for the remainder. Treat it as a safety net, and keep checking the petrol pump.
- As soon as you realise, stop: less petrol inside your tank makes a thinner mixture. What to do next doesn't change, though — still don't fire it up.
Petrol already in a diesel around Smallwood? Start here
Then, there's only a short order of things. Starting it is out, and so is switching on your ignition. If you are still at the forecourt — the nearest petrol station or anywhere else — ask the staff to help you roll the car away from the pump. Next, 0333 366 0103. We'll ask what went in, roughly how much, and if it's been run.
If it was AdBlue rather than petrol, say so. That is a separate problem — corrosion and deposits instead of lost protection — and it has its own page for Smallwood.
Smallwood petrol in a diesel tasks: why one costs more than another
There is no fair single quote for this, because the four scenarios above are four separate tasks. Which of them you're in is chiefly what moves your cost. Where your car is counts too, and whether a technician can safely reach it, after the ratio of petrol to what the tank holds.
That is why our engineers ask three questions before quoting instead of after: what went in, how much, and if it's run. Those answers turn a range into a straight figure.
About Smallwood itself
Smallwood is a suburban area in the West Midlands region of England, situated approximately 12 miles south of Birmingham. Smallwood sits at an elevation of around 124 metres, in a gently sloping landscape of inland Worcestershire. Smallwood is characterized by a high proportion of flat housing, which reflects its development as a residential area. Smallwood is close to nearby places such as St Georges and Redditch, and is about 95 miles northwest of London.
Smallwood and Worcestershire: where our fuel drain cover runs
The teams answering petrol in diesel calls in Smallwood, in the B postcode area, also work the places near it, St Georges, Redditch and Lodge Park among them. A forecourt, a supermarket car park, a lay-by or your own drive are all spots our engineers work, and the car doesn't need to come to us.
Smallwood: still at the petrol pump?
Nothing beats it: that's where you now are. Keep the car switched off, and ring.