Petrol in a Diesel Car in Walton: How Worried Should You Be?
Far less than you likely are, if it has not been started. "Have I wrecked it?" is the first question anyone in Walton asks, and the honest answer is generally no, since petrol resting in a diesel tank hurts nothing till it is dragged through the fuel system — by ignition priming, by your starter, or by being driven. Leave your motor off and ring Petrol in Diesel — that keeps it that way. What petrol really does to a diesel, how to gauge how far it has travelled, and how to stop it from happening again: that is the rest of this page.
Petrol in a diesel: what does it do to the engine?
Two tasks fall to diesel on its route round a motor. It lubricates to begin with, and only then does it burn. What stops the surfaces inside the high-pressure fuel pump and the fuel injectors from grinding against each other is the diesel flowing through them — they're designed to very fine tolerances.
The second job petrol does not do at all, and the first it does badly. It is runnier than diesel and takes away the lubrication the fuel system rests on, so a pump running on a petrol mixture is a pump wearing itself. And petrol is designed 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 plain once you put those together. It's movement that does the harm, not contact. Any tank with petrol in it is a fuel issue. A pump that has been running on that petrol is the beginning of a mechanical one, and whatever a worn pump sheds travels on with your fuel to the injectors downstream.
Four situations our technicians see in Walton: how serious is petrol in a diesel?
Filled up, and not started: no case is better. On a forecourt, and genuinely only there, the petrol is still confined to the tank — because anywhere else the car was driven to reach it. The task is emptying and rinsing on the spot.
Ignition on, or started for a moment. With the fuel system primed, your lines and filter already contain petrol that came from that tank. Still usually straightforward: drain, flush, and the filter seen to.
Those few miles on the road meant your pump labouring on fuel weakened by petrol throughout. How hard your car was driven matters as much as how far, and this work takes in that tank, your lines, the fuel filter and fresh fuel through the entire system. Driving the kids to Old Hall Junior School is one sort of trip. Very different a second time: a run to Sheffield, under 15 miles away, or some mileage on the M1, under 10 miles from Walton, where your engine never stopped labouring hard.
Driven on until it protested — rattling, smoke, a ragged idle, a soft throttle. The fuel isn't acting like diesel any more, and your motor is saying so. Stop where you are — on the verge on Lindrick Gardens, at the kerb, down a side road — and do not move it. What goes first is still the fuel drain and flush, and that takes care of it, with permanent damage very unusual if a vehicle is stopped early.
Stories Walton people hear about petrol in a diesel
It will not be fine. The myth: "Fill it the rest of the way with diesel and it will be." Topping up takes out nothing; it gives you a fuller tank of the same mix. The assumption behind the 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 modern diesels, not less, since their fuel passes through more precise parts at higher pressure.
"It starts, it drives, so no harm done" — the myth that catches more motorists than any other. Feed diesel to a petrol motor and it usually won't run, and so the driver stops — and the damage stops with them. While the pump grinds, a diesel fed petrol usually starts, ticks over and drives away as though nothing has happened. Running does not mean fine.
"A drop of two-stroke oil and drive it home" — a myth, taken from a fix from years ago, for a separate fault. It does not put back what petrol has thinned, and that petrol is still inside your tank afterwards.
The next start draws petrol back round the pump from the lines and the filter, where some of it sits once the engine has been run. That is why draining the tank yourself doesn't leave you sorted — a myth. It is also really risky to drain petrol into a can by the kerbside.
Petrol in a diesel: how does it happen?
It's rarely carelessness, and nobody does it on purpose. One way only, because of the nozzles: the smaller petrol one slips inside a diesel filler with almost no resistance, whereas the diesel one mostly won't fit a petrol motor. That is how the forecourt makes it easy.
It occurs when habit and your car stop matching. A new vehicle, a hire car or a courtesy car. Households running one of each, petrol and diesel. Your usual forecourt, its pumps now in a different order. A rushed fill en route to Chesterfield with a train to catch. The first fill-up in a diesel Volkswagen Tiguan after years of driving petrol is precisely the moment it happens. Your hand does what it has always done when you add rain, a phone call or a back seat full of children.
Walton people: how to avoid petrol in a diesel next time
- Green for unleaded and black for diesel is usual in the UK — but not on every forecourt. Trust the label on the pump, not the colour.
- Inspect your filler flap. Many cars state the fuel inside the flap or on the cap. Look at it on the first fill in a vehicle you don't know.
- Good intentions do less than a sticker or a fob in a bright colour on your diesel's key when a home has one of each. So mark it.
- Say it before you lift it. On the first fill in a new or hired car, say "diesel" aloud before you take the nozzle off the petrol pump. It sounds silly and it works.
- Mistakes like this are simple 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 safety net, not a reason to stop checking the pump.
- Less petrol makes a weaker mix, and so stop the moment you realise — though remembering that the next step is unchanged. It's still not to fire it up.
Put petrol in a diesel in Walton already?
In that case, there is only a short order of things. Leave it unstarted, with your ignition off too. If you're still on the forecourt — BP or anywhere else — ask the staff to help you push the car clear of the petrol pump. What went in, roughly how much, and whether it has run: tell us those when you ring 0333 366 0103.
If it was AdBlue instead of petrol, say so. That's a separate issue — corrosion and deposits and not lost lubrication — and it has its own page for Walton.
What makes one Walton petrol in a diesel job cost more than the next
The four scenarios above are four separate tasks, so no single quote for this would be honest. The scenario itself does most of the work of moving the cost. Where your car is counts too, and whether our van can safely reach it, after the proportion of petrol to what that tank takes.
Ahead of any quote, not after, we ask three queries: the fuel that was put in, its quantity, and if it has run. That is why. A range becomes a straight figure when those replies are in.
About Walton, briefly
Walton is a suburban area in Derbyshire, situated on the riverside with an elevation of around 130 metres. Walton lies approximately 11 miles from Sheffield and is close to nearby places such as Brookside, Brampton, and Boythorpe. Walton has a population of around 4220 people and is characterised by predominantly detached housing.
Fuel drain cover across Derbyshire, Walton included
Petrol in diesel jobs around Walton — part of the S postcode area — go to vans that likewise cover the spots around it, Brookside, Brampton and Boythorpe among them. You need not move your car to us. Forecourts, supermarket car parks, lay-bys and your own driveway are all locations where we work.
Walton: still at the petrol pump?
Then, you couldn't be in a better place. Ring, and keep it switched off.