Should You Worry? Petrol in a Diesel Car in Caldercruix
If it hasn't been started, worry less than you probably are. Till your ignition primes your pump, your starter cranks, or the car is driven, petrol in a diesel tank just rests there and does nothing. Which means the honest reply to that first Caldercruix question — "have I ruined it?" — normally no. Leave the engine off then phone Petrol in Diesel — that keeps it that way. The rest of this page explains what petrol really does to a diesel, how to tell how far it has got, and how to make sure it doesn't happen to you a second time.
Inside your engine: what petrol in a diesel really does
Diesel does two tasks on its way through a motor. Before it burns, it lubricates — then it ignites. Your high-pressure pump and your injectors are designed to extremely fine clearances, and the diesel passing through them is what stops those surfaces from wearing down against each other.
Of those two jobs, petrol manages the first badly and the second not at all. Being less viscous than diesel, petrol strips out the protection a fuel system needs, so a pump running on the mixture to wear itself. It's equally made to resist igniting under compression — the reverse of what a diesel needs — which is where you get the knocking.
Taken together, they make clear what shape the trouble takes. It's circulation that does the harm, not contact. Where the petrol is only in that tank, it is an issue of fuel, nothing more. Whatever a worn pump sheds goes on, carried by the fuel, into your injectors downstream, which is why a pump that has worked on that petrol is where a mechanical problem starts.
How bad is petrol in a diesel? Four situations our technicians see in Caldercruix
Filled but not once started — as good as it gets. The petrol is inside that tank and only the tank, and the task is a drain and a flush where your car sits. This is the one situation that can only really occur on a forecourt, as anywhere else the vehicle has been driven to get there.
Ignition on, or started for a moment. Your system has been bled, so petrol has left that tank and reached your filter and the lines. That is generally still an easy job — a drain, a flush, and the filter dealt with.
Driven a few miles. Now your pump has spent those miles running on diluted fuel. Miles is only half of it; how hard it was driven counts just as much. Either way the work runs to the tank, the lines, your filter and clean fuel through the entire system. On the school run to the local primary school, the mileage is short. A run as far as Glasgow, under 15 miles away, is a very different task. So is any miles on the M8, under 3 miles from Caldercruix, where your engine has been working hard throughout.
It complained, and only then stopped: smoke, rattling, a throttle gone soft, an idle gone ragged. That's the motor telling you its fuel no longer is behaving like diesel. Pull up on the spot — on the verge on Station Road, at the kerb, down a side road — and do not move it again. Long-term damage is very uncommon when a vehicle is pulled over quickly, and the fuel drain and flush that still come first deal with it.
Caldercruix drivers and the petrol in a diesel stories they hear
"Top it up the rest of the way with diesel and it'll be fine" — a myth. It won't. Nothing is removed by topping up — you're left with a bigger tank, still the same mix. Percentage isn't how a diesel fuel system tolerates petrol, whatever that guidance assumes.
"Current diesels can handle a little petrol" — a myth, and nearer the reverse. Protection counts more on newer diesels, not less, because their fuel passes through more precise parts at higher pressure.
"It starts, it drives, and so no harm done" — the myth that trips up most people than any other. Diesel in a petrol motor usually leaves a motor that will not run: the motorist stops, and so does the harm. While your pump wears, a diesel fed petrol normally starts, ticks over and drives away as though nothing has happened. Being able to run isn't proof of being fine.
"A drop of two-stroke oil and drive it home" — a myth, borrowed from a fix from years ago, for a different problem. The petrol is still in your tank after that, and whatever it has diluted is not put back.
Once the engine has run, part of the petrol sits in your filter and your lines, not your tank — and the next start sends it straight back through the pump. So the myth "drain the tank yourself and you're sorted" does not hold. Also, a can of petrol filled at the kerbside is truly dangerous.
Why petrol in a diesel takes place so easily
Carelessness is seldom the cause, and no one means to do it. The forecourt makes it simple: the petrol nozzle is the slimmer of the two, and it slides into a diesel filler with almost no resistance, whilst a diesel nozzle mostly won't go into a petrol car at all. So the error runs one way.
Routine and the car falling out of step is when it happens. Courtesy car, hire car, or a motor that is brand new. One petrol and one diesel on the driveway of the same household. Your usual forecourt, its pumps suddenly in a different order. A train to catch, and a rushed fill on the way to the nearest station. The first fill-up in a diesel Volkswagen Golf after years of driving petrol is exactly the moment it takes place. Add rain, a phone call or a back seat full of kids, and the hand repeats what it has always done.
Caldercruix people: how to avoid petrol in a diesel next time
- Read the pump, not the colour. In the UK unleaded handles are normally green and diesel black, yet not on every forecourt. The label is what matters.
- In a vehicle you don't know, look inside the flap over the filler or at the cap before the first fill: many motors state the fuel there.
- One of each in the household? Mark the key to the diesel — a coloured fob, a sticker — since meaning to remember isn't enough.
- It sounds silly and it works: on the first fill in a new or hired car, say "diesel" out loud before you take the nozzle off the petrol pump.
- Whilst you're thinking about something else, this is an easy mistake to make — so put the phone away.
- A misfuel inhibitor helps, up to a point. Some diesels come with a filler designed to refuse a petrol nozzle, and add-on devices are available for cars without one. They are a safety net, not a reason to stop checking the pump.
- Stop as soon as you realise. Less petrol inside your tank makes a weaker mix. It doesn't change what to do next, which is still not to start the vehicle.
Put petrol in a diesel around Caldercruix already?
Then, there is only a short order of things. Do not switch your ignition on, and do not start it. Ask the attendants to help you roll it away from the pump if you are still on the forecourt, whether that's BP or anywhere else. Next, 0333 366 0103. We'll ask what got in, roughly how much, and if it has been run.
Say so if it was AdBlue rather than petrol: it is a separate fault, with its own page for Caldercruix, because AdBlue brings corrosion and deposits rather than lost protection.
What makes one Caldercruix petrol in a diesel task cost more than the next
A fair single price does not exist here: four situations, four separate jobs. The situation itself does most of the work of moving the cost. Two things follow that: the petrol that was put in as a proportion of what that tank holds, then the spot your car is in and whether a van can reach it safely.
That's why our engineers ask three queries before costing rather than after: what got in, how much, and whether it has run. A range turns into a straight figure when the replies are in.
About Caldercruix, briefly
Caldercruix is a village in North Lanarkshire, situated on the shores of a lake at an elevation of 187 metres, with semi-detached housing being the predominant type of accommodation. Caldercruix lies near the villages of Hillend, Longriggend, and Plains, and is approximately 13.7 miles from Glasgow. Caldercruix has a population of around 2015 people, and its location near a lake makes it a notable lakeside community in the area. Caldercruix is also relatively distant from major cities in England, with London being around 339.4 miles away.
Caldercruix and North Lanarkshire: where our fuel drain cover reaches
Petrol in diesel calls in Caldercruix — part of the ML postcode area — go to teams that also cover the locations about it, Hillend, Longriggend and Plains included. A forecourt, a supermarket car park, a lay-by or your own drive are all places our engineers drain, and the vehicle does not need to move to us.
At the petrol pump in Caldercruix, still?
No position is better: that is where you are. Keep it off. Call.