Should You Worry? Petrol in a Diesel Car in Cat Bank
If it has not been started, worry less than you likely are. Until your ignition primes your pump, the starter cranks, or your vehicle is driven, petrol in a diesel tank simply sits there and does nothing. Which makes the honest reply to that first Cat Bank query — "have I ruined it?" — usually no. Petrol in Diesel is who to ring, with the engine left off, and so it stays that way. What petrol really does to a diesel, how to judge how far it's gone, and how to stop it from happening a second time: that's the remainder of this page.
Inside the engine: what petrol in a diesel does
Diesel does two tasks on its way through a motor. Before it combusts, it lubricates — then it combusts. What keeps the surfaces inside your high-pressure pump and your injectors from wearing down against one another is your diesel passing through them — they are made to extremely fine gaps.
The second task petrol does not do at all, and the first it does poorly. It's thinner than diesel and removes the lubrication the system depends 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 clattering comes from.
Seen together, they make clear what shape the trouble has. Contact does not do the harm — circulation does. All a tank with petrol in it amounts to is a fuel problem. 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 the fuel to the fuel injectors downstream.
Cat Bank, petrol in a diesel: four cases, from mild to significant
Filled up, and not started: no case is better. That petrol is inside the tank and just the tank, and the task is a drain and a flush where the car sits. This is the one situation that can only truly occur on a forecourt, as anywhere else your car has been driven to get there.
Started for a moment, or only your ignition on. With the fuel system primed, your lines and filter already contain petrol that has come from the tank. That is usually still an easy task — a drain, a flush, and the filter dealt with.
Driven a few miles. Now the pump has spent these miles labouring on weakened fuel. Mileage is only half of it; how hard it was driven matters just as much. Either way the work includes your tank, the fuel lines, the fuel filter and fresh fuel through the whole circuit. A school run to Coniston CofE Primary School is one thing. A run as far as Lancaster, under 25 miles away, is a very different job. So is any miles on the M6, under 25 miles from Cat Bank, where the motor has been labouring hard throughout.
It protested, and only then stopped: smoke, clattering, a throttle gone soft, an idle gone lumpy. The motor is telling you your fuel is no longer behaving like diesel. Leave it where it stops: a lay-by, a quiet street, the verge on Ruskin Avenue. The drain and flush still go first, and they take care of it: when a car is pulled over early, long-term damage is very rare.
Petrol in a diesel myths Cat Bank drivers hear
It will not be fine. The myth: "Fill it the rest of the way with diesel and it'll be." Topping up removes nothing; it gives you a bigger tank of the same mix. A diesel fuel system does not accept petrol by percentage in the way that guidance presumes.
Myth: "A modern diesel can cope with a bit of petrol." If anything, the reverse. A modern diesel runs its fuel through smaller parts at higher pressure, which makes the lubrication matter more, not less.
Myth: "If it starts and drives, there is no damage done." This is the one that catches motorists. Feed diesel to a petrol motor and it generally will not run, and so the motorist stops — and the harm stops with them. Whilst the pump grinds, a diesel fed petrol normally starts, idles and drives away as if nothing has happened. Running doesn't mean fine.
"A drop of two-stroke oil and drive it home" — a myth, taken from a fix from years ago, for a separate issue. It doesn't put back what petrol has diluted, and that petrol is still inside that tank later.
Once the engine has been run, part of the petrol is in your filter and your lines, not the tank — and your next start sends it right back through your pump. So the myth "drain that tank yourself and you're sorted" doesn't hold. Draining petrol into a can by the roadside is also really risky.
How does petrol in a diesel occur?
Carelessness is rarely the cause, and nobody means to do it. One way only, because of the nozzles: the slimmer petrol one slips inside a diesel filler with almost no resistance, whereas the diesel one generally won't fit a petrol vehicle. That is how the forecourt makes it easy.
It happens when habit and the vehicle stop matching. Hire cars, courtesy cars, and motors that are new to you. Two motors on one driveway, one petrol, one diesel. Your normal forecourt, its pumps now in a different order. Rushing for a train at Windermere and filling up en route. The first fill-up in a diesel Volkswagen Golf after years of driving petrol is exactly the moment it happens. With rain, a call coming in, or children to deal with, your hand simply does what it has always done.
Next time you fill up around Cat Bank: preventing petrol in a diesel
- Green for unleaded and black for diesel is usual in the UK — yet not on each forecourt. Go by the label on the petrol pump, not the colour.
- Many motors state the fuel type inside the filler flap or on the cap, so check there on your first fill in a car you do not know.
- Good intentions count for less than a sticker or a fob in a vivid colour on your diesel's key when a household has one of each. So mark it.
- It seems daft and it works: on your first fill in a new or hired car, say "diesel" aloud before you take the nozzle off the pump.
- Mistakes like this are straightforward to make whilst your mind is on something else, and so the phone goes away.
- Up to a point, a misfuel inhibitor helps: some diesels come with a filler built to block a petrol nozzle, and aftermarket devices exist for the rest. Treat it as a backstop, then keep checking the pump.
- Spotting it halfway? Stop at once. A weaker mixture results from less petrol in the tank, but the next stage remains the same: do not fire it up.
Cat Bank: already put petrol in a diesel?
Then, there is just a short order of things. Leave it unstarted, with your ignition off too. If you are still on the forecourt — BP or anywhere else — ask the attendants to help you roll the vehicle clear of the petrol pump. What went in, about how much, and if it's run: tell us those when you phone 0333 366 0103.
Corrosion and deposits form the issue with AdBlue, whereas petrol means lost lubrication. So if it was AdBlue, say so — and see its own Cat Bank page.
Why one petrol in a diesel task in Cat Bank costs more than another
A fair single price doesn't exist here: four scenarios, four separate tasks. The scenario itself does most of the work of moving your cost. Two things come after that: the petrol that went in as a share of what the tank holds, then the spot your car is in and whether a technician can get to it safely.
Before any quote, not after, come three questions: the fuel that got in, the volume, and if it has run. That is why. With those replies, there is a straight figure rather than a range.
About Cat Bank itself
Cat Bank is a small lakeside locality in Cumbria, situated near Coniston and Oak Bank, with semi-detached housing being the predominant type. Cat Bank sits at an elevation of 54 metres, close to the shores of Coniston Water, and is approximately 24.5 miles from Lancaster. Cat Bank is part of a scenic area that attracts visitors to the Lake District, with nearby Haws Bank also being a popular destination. Cat Bank has a population of around 595 residents, who enjoy the tranquil surroundings of the locality.
Fuel drain cover in Cat Bank and across Cumbria
Cat Bank rests in the LA postcode area, and the vans that answer petrol in diesel calls there work the places around it as well — Coniston, Oak Bank and Haws Bank among them. The vehicle does not need to move to us: our engineers drain at a forecourt, in a supermarket car park, in a lay-by or on your own driveway.
In Cat Bank and still at the petrol pump?
Then, you couldn't be in a better place. Keep it off. Ring.