How Worried Should You Be? Petrol in a Diesel Car in Town Centre
If it has not been started, you can worry less than you likely are. "Have I ruined it?" is the first question everyone around Town Centre asks, and the truthful answer is usually no, because petrol left in a diesel tank hurts nothing till it's drawn through your fuel system — by ignition priming, by the starter, or by driving. To leave the vehicle that way, ring Petrol in Diesel and leave the engine switched off. Below, this page sets out what petrol actually does inside a diesel, how far it may have gone, and how to stop it happening to you a second time.
Inside the motor: what petrol in a diesel does
Diesel does two jobs on its way through a motor. It lubricates to begin with, and only then does it burn. Made to very fine gaps, your injectors and the pump depend on the diesel flowing through them to keep their surfaces from wearing against one another.
Of those two jobs, petrol handles the first poorly and the second never. It's thinner than diesel and strips away the lubrication the system rests on, and so a pump running on a petrol mixture is a pump wearing itself. And petrol is made to resist igniting under compression, which is the opposite of what a diesel needs from its fuel. That's where the knocking comes from.
Put these together and the shape of the problem is plain. It's circulation that causes the damage, not contact. Petrol in the tank is a fuel problem. A pump that has been working on that petrol is the start of a mechanical one, and whatever a worn pump sheds moves on with the fuel to the injectors downstream.
How serious is petrol in a diesel? Four scenarios we see around Town Centre
Fuelled, and not started: nothing beats it. At a forecourt, and really only there, that petrol is still limited to the tank — since anywhere else your car was driven to get to it. The job is draining and rinsing on the spot.
A moment's running, or just your ignition on. With the fuel system primed, the fuel lines and filter now hold petrol that has come from that tank. Still usually easy: drain, flush, and the fuel filter dealt with.
Driven a couple of miles. Now your pump has spent those miles labouring on diluted fuel. The work is that tank, the fuel lines, the filter and fresh fuel through the entire circuit, and how hard the vehicle was driven matters as much as how far. On the school run to Cramlington Shanklea Primary School, the mileage is short. Any mileage on the A167(M), under 10 miles from Town Centre, means the motor has worked hard throughout, and a run to Newcastle upon Tyne, under 10 miles away, makes a very different job too.
Knocking, an uneven idle, smoke, a throttle gone soft: driven till it complained. The fuel isn't behaving like diesel any more, and your engine is telling you. Whether it's the verge on Station Road, a lay-by or a side road, stop where you are and leave it. The fuel drain and flush still come first, and they deal with it: if a vehicle is stopped quickly, long-term damage is very uncommon.
Petrol in a diesel stories Town Centre people hear
It will not be fine. The myth: "Fill it the rest of the way with diesel and it'll be." Nothing is removed by topping up — you're left with a fuller tank, still the same mixture. That advice supposes a diesel fuel system tolerates petrol by percentage. It doesn't.
If anything, the reverse holds. Myth: "A modern diesel can cope with a bit of petrol." A modern diesel sends its fuel through smaller components at higher pressure, which makes the protection matter more, not less.
Myth: "If it starts and drives, there's no damage done." This is the one that catches people. The motorist of a petrol motor fed diesel usually has no choice but to stop, because it will not run, and the damage stops there. Nothing seems to have happened when a diesel fed petrol fires up, ticks over and drives away, as it usually does; meanwhile your pump grinds. Being able to run isn't the same as being fine.
Myth: "Add some two-stroke oil and drive the vehicle home." It's an old fix for a different problem. None of what petrol weakened gets put back by it — and afterwards, that tank still contains the petrol.
Myth: "Drain the tank yourself and you're sorted." Once your engine has been run, some of that petrol is no longer in the tank: it is in the filter and your lines, and it goes straight back through the pump on the next start. It's also really risky to drain petrol into a can by the roadside.
Petrol in a diesel: how does it take place?
Nobody does it on purpose, and it's seldom carelessness. The petrol nozzle is the smaller of the two and slides into a diesel filler with almost no resistance; a diesel nozzle mostly won't go into a petrol motor at all. The forecourt makes it simple, and the slip runs one way.
It happens when routine and the vehicle stop matching. Courtesy car, hire car, or a vehicle that's new. A household with one petrol and one diesel on the drive. A well-known forecourt with the pumps in a different order. A train to catch, and a hurried fill on the way to Cramlington. The first fill-up in a diesel Volkswagen Golf after years of driving petrol is exactly the moment it takes place. The hand repeats what it has always done once you add rain, a phone call or a back seat full of kids.
Next time you fill up around Town Centre: avoiding petrol in a diesel
- Not every forecourt in the UK keeps to green for unleaded and black for diesel, though most generally do. Check the petrol pump's label; the colour is just a hint.
- In a car you don't know, look inside the flap over your filler or at the cap before your first fill: many vehicles print the fuel there.
- Good intentions count for less than a sticker or a fob in a vivid colour on the diesel's key if a house has one of each. So mark it.
- "Diesel", aloud, before you lift the nozzle — each time a new or hired car needs its first tank. It seems silly. It does the trick.
- Mistakes like this are straightforward to make whilst your mind is on something else, and so your phone goes away.
- A misfuel inhibitor helps, up to a point. Some diesels have a filler designed to refuse a petrol nozzle, and add-on devices exist for cars without one. They are a backstop, not a reason to stop reading the pump.
- Spotting it mid-fill? Stop there and then. A thinner mix results from less petrol in that tank, but the next stage remains the same: do not fire it up.
Town Centre: already put petrol in a diesel?
Short and simple, then, is the order of things. Don't fire it up, and don't turn the ignition on. Ask the attendants to help you push it away from the petrol pump if you're still at the forecourt, whether that's Sainsbury's or somewhere else. Then ring 0333 366 0103 and tell us what got in, about how much, and if it's run.
Say so if it was AdBlue rather than petrol: it's a different fault, with its own page for Town Centre, since AdBlue brings corrosion and deposits rather than lost lubrication.
One petrol in a diesel task in Town Centre costs more than another. Why?
There is no honest single price for this, since the four situations above are four different jobs. What shifts your cost is chiefly which of them you are in. Beyond that it's the ratio — how much petrol was put in against how much that tank holds — and then where the car is and whether our van can reach it safely.
That is why we ask three questions before quoting instead of after: what got in, how much, and if it has run. Those replies turn a range into a straight figure.
About Town Centre and where it is
Town Centre is a suburban area located inland in Northumberland, England, with a relatively low elevation of 74 metres. Town Centre sits approximately 7.6 miles from Newcastle upon Tyne, in close proximity to nearby places such as Cramlington and Parkside Chase. Town Centre has a population of around 4340 residents, predominantly living in semi-detached housing. Town Centre is also situated about 254.6 miles from London, making it a relatively distant suburb from the capital city.
Fuel drain cover across Northumberland, Town Centre included
Cramlington, Parkside Chase and Whitelea Dale are among the places around Town Centre that the same vans work, answering petrol in diesel call-outs across Town Centre's NE postcode area. No need to bring the car to us. Forecourts, supermarket car parks, lay-bys and your own driveway are all locations where we work.
Still at the pump in Town Centre?
The best position there is, then — that is where you are. Call, and keep it turned off.