Should You Worry? Petrol in a Diesel Car in Oxford
Unstarted? Then less anxious than you probably feel. Petrol resting in a diesel tank does nothing to your engine till something pulls it through the fuel system — the ignition priming your pump, the starter, or the drive itself. So the honest answer to the first question everyone around Oxford asks, "have I wrecked it?", is normally no. Petrol in Diesel is who to ring, with the motor kept off, so it remains that way. Keep reading for three things: the effect petrol has inside a diesel engine, the signs of how far it has spread, and ways to make sure you never repeat it.
Inside your engine: what petrol in a diesel really does
Two tasks fall to diesel on its journey round a motor. Before it ignites, it protects — then it burns. What stops the surfaces inside your high-pressure pump and the fuel injectors from wearing down against one another is your diesel flowing through them — they're built to extremely fine clearances.
The second job petrol does not do at all, and the first it does poorly. The clattering comes from petrol being made not to ignite when compressed, which is exactly the reverse of what a diesel needs. On top of that it is runnier than diesel, it strips away the lubrication your system rests on, and any pump working on that mixture is wearing itself.
Put these together and the shape of the problem is plain. Not contact but movement is what does the damage. All a tank with petrol in it amounts to is a fuel issue. A pump that has been working on that petrol is the beginning of a mechanical one, and whatever a worn pump sheds travels on with your fuel to the fuel injectors further on.
Four situations we see around Oxford: how serious is petrol in a diesel?
Fuelled, and not started: nothing beats it. At a forecourt, and genuinely only there, the petrol is still limited to that tank — because everywhere else your car was driven to get to it. The task is emptying and rinsing on the spot.
A brief spell of running, or merely the ignition on. The system has been primed, and so petrol has left your tank and reached your filter and the fuel lines. Still normally simple: drain, flush, and the fuel filter dealt with.
Driven a few miles. Now your pump has spent these miles labouring on thinned fuel. The work is that tank, the lines, the fuel filter and clean fuel through the entire circuit, and how hard the car was driven counts as much as how far. On the school run to St Ebbe's Church of England Aided Primary School, the miles is short. Any distance on the Wheatley Spur, under 10 miles from Oxford, means the motor has worked hard throughout, and a run to Milton Keynes, under 50 miles away, is a very different task too.
Knocking, a lumpy idle, smoke, a throttle gone soft: driven till it complained. The engine is telling you your fuel is no longer acting like diesel. Whether it's the verge on Carfax, a lay-by or a side street, stop there and leave it. The fuel drain and flush-through still come first, and they sort it out: when a vehicle is stopped early, lasting damage is very rare.
Myths Oxford motorists hear about petrol in a diesel
"Top it up the rest of the way with diesel and it will be fine" — a myth. It will not. Nothing comes out when you top up — the tank simply holds more of the same mixture. The idea behind that advice — that diesel fuel systems accept petrol by percentage — is wrong.
If anything, the reverse is true. Myth: "A newer diesel can cope with a bit of petrol." At higher pressure, through smaller parts: that's how a modern diesel moves its fuel, and so the protection matters for more, not less.
One myth that catches motorists off guard: if it starts and drives, it must be unharmed. The driver of a petrol motor fed diesel usually stops, since it will not run, and the harm 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 wears. A running engine does not mean fine.
Myth: "Add some two-stroke oil and drive it home." It's an outdated fix for a different issue. None of what petrol thinned is put back by it — and afterwards, that tank still holds that petrol.
Myth: "Drain your tank yourself and you're sorted." Once your engine has run, some of the petrol is no longer in that tank: it's in the fuel filter and the fuel lines, and it goes right back through your pump at the next start. And, a can of petrol filled at the kerbside is truly dangerous.
How does petrol in a diesel happen?
Carelessness is seldom the cause, and no one means to do it. One way only, because of the nozzles: the narrower petrol one slides inside a diesel filler with almost no resistance, while the diesel one mostly will not fit a petrol vehicle. That is how the forecourt makes it simple.
When routine and the vehicle stop matching, it happens. A car that's new to you — a hire car, on loan as a courtesy car, or brand new. One petrol and one diesel on the driveway of the same household. A well-known forecourt with the pumps in a different order. Racing for a train outside the nearest station and fuelling up en route. Exactly the moment it happens: after years of driving petrol, someone fills a diesel Volkswagen Golf for the first time. With rain, a call coming in, or children to deal with, the hand just does what it always has.
Avoiding petrol in a diesel next time you fill up in Oxford
- Not every forecourt in the UK keeps to green for unleaded and black for diesel, though most usually do. Read the petrol pump's label; the colour is only a clue.
- Check your filler flap. Plenty of vehicles state the fuel inside the flap or on the cap. Look at it on your first fill in any vehicle you do not know.
- A coloured fob or a sticker on the diesel's key achieves more than any amount of intending to remember, in a house with one of each.
- "Diesel", aloud, before you pick up the nozzle — every time a new or hired car gets its first tank. It sounds silly. It does the trick.
- Thinking about something else is when this becomes an easy mistake to make, so tuck your phone away and keep your mind on the pump.
- Some diesels have a filler designed to refuse a petrol nozzle, and devices you can add exist for vehicles without one. Such an inhibitor helps up to a point — as a backstop, not a reason to stop checking the petrol pump.
- Spotting it mid-fill? Stop at once. A thinner mix results from less petrol in your tank, yet the next step remains the same: do not fire it up.
Petrol already in a diesel in Oxford? Start here
Short and simple, then, is the order of things. Leave it unstarted, with your ignition switched off too. If you're still at the forecourt — BP or anywhere else — ask the staff to help you push the car away from the petrol pump. What went in, roughly how much, and if it's run: tell us those when you ring 0333 366 0103.
If it was AdBlue rather than petrol, say so. That's a different issue — corrosion and deposits and not lost lubrication — and it has its own page for Oxford.
Why one petrol in a diesel task in Oxford costs more than another
The four scenarios above are four separate tasks, so no single price for this would be honest. Mostly, the cost moves with which situation you're in. Where your car is matters too, and whether a technician can safely reach it, after the ratio of petrol to what that tank takes.
Ahead of any quote, not after, we ask three queries: your fuel that was put in, its volume, and if it has run. That is why. The replies change a range into a straight figure.
About Oxford itself
Oxford is a city situated in the South East of England, on the River Thames, with a diverse range of architectural styles, including many terraced houses. Oxford sits at an elevation of around 73 metres, approximately 51 miles west of London, and is connected to nearby places such as New Osney, Grandpont, and Jericho. Oxford has a population of around 82,407 people and is a major urban centre in the region. Oxford is also close to other cities, including Milton Keynes, which is about 29 miles away.
Oxford and Oxfordshire: where our fuel drain cover reaches
Oxford rests in the OX postcode area, and our vans that answer petrol in diesel jobs there work the locations around it as well — New Osney, Grandpont and Jericho among them. We drain where your vehicle is — your own driveway, a lay-by, a supermarket car park, a forecourt — so it never needs to come to us.
Still at the petrol pump in Oxford?
Then, you could not be in a better position. Switched off it remains; then phone.