How Worried Should You Be? Petrol in a Diesel Car in Cairneyhill
Less than you probably are, if it hasn't been started. Petrol resting in a diesel tank does nothing to your motor until something pulls it through your fuel system — your ignition priming the pump, your starter, or the drive itself. So the truthful answer to the first query anyone in Cairneyhill asks, "have I ruined it?", is generally no. Leave your motor off and phone Petrol in Diesel — that keeps it that way. Below, you will find what petrol actually does inside a diesel, how far it may have got, and how to stop it happening to you a second time.
Petrol in a diesel: what does it do to your engine?
Passing through a motor, diesel is doing two jobs at once. It protects first, and only then does it burn. What stops the surfaces inside your high-pressure pump and the fuel injectors from grinding against one another is the diesel flowing through them — they are designed to very fine tolerances.
Petrol does the first task badly and the second not at all. It's thinner than diesel and strips away the lubrication your fuel system rests on, and so a pump running on a petrol mix is a pump wearing itself. And petrol is made to resist igniting under compression, which is the reverse of what a diesel needs from its fuel. That is where the knocking comes from.
Put those together and the shape of the trouble is clear. It is movement that does the harm, not contact. Petrol in the tank is a fuel issue. 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 your fuel to the fuel injectors further on.
Four scenarios our technicians see in Cairneyhill: how serious is petrol in a diesel?
Filled up, and not started: no case is better. At a forecourt, and truly only there, that petrol is still limited to your tank — since everywhere else the car was driven to get to it. The task is draining and flushing on the spot.
Ignition on, or started for a second. The fuel system has been primed, and so petrol has left that tank and got to the filter and your lines. Usually nothing more than clearing, cleaning and sorting the filter, so still easy.
A few miles driven, and your pump has spent every one of them working on thinned fuel. Distance is only half of that; how hard it was driven counts just as much. Either way the work runs to that tank, the lines, the filter and clean fuel through the entire system. Driving the kids to the local primary school is one kind of trip. Very different once more: a run to Dunfermline, under 3 miles away, or any miles on the A823(M), under 5 miles from Cairneyhill, where the engine kept labouring hard.
Rattling, an uneven idle, smoke, a throttle gone soft: driven until it complained. The motor is telling you the fuel is no longer behaving like diesel. Whether it's the verge on Brandy Riggs, a lay-by or a side road, stop where you are then leave it. What comes first is still the fuel drain and flush-through, and that sorts it out, with permanent damage very rare when a vehicle is pulled over early.
Petrol in a diesel stories Cairneyhill drivers hear
Myth: "Fill it the rest of the way with diesel and it will be fine." It will not. A fuller tank of the same mixture is all you get, because topping up takes out nothing. The assumption behind the guidance — that diesel fuel systems tolerate petrol by percentage — is wrong.
"Current diesels can handle a little petrol" — a myth, and nearer the reverse. At higher pressure, through more precise components: that's how a modern diesel moves its fuel, and so the lubrication matters for more, not less.
Myth: "If it starts and drives, there is no harm done." This is the one that catches drivers. Feed diesel to a petrol motor and it usually won't run, so the driver stops — and the harm stops with them. While the pump wears, a diesel fed petrol normally starts, idles and drives away as though nothing has happened. Running doesn't mean fine.
An old workaround for a separate issue is behind this one. Myth: "Add some two-stroke oil and drive the car home." It doesn't put back what petrol has thinned, and that petrol is still in the tank later.
Myth: "Drain that tank yourself and you're sorted." Once the motor has run, some of the petrol is no longer inside the tank: it is in the filter and the fuel lines, and it goes straight back through your pump at the next start. It is also really dangerous to drain petrol into a can by the kerbside.
Petrol in a diesel: how does it take place?
Carelessness is rarely the cause, and no one means to do it. One way only, because of the nozzles: the slimmer petrol one slips inside a diesel filler with almost no resistance, while the diesel one generally will not fit a petrol motor. That is how the forecourt makes it straightforward.
It occurs when habit and the 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. Fuelling up in a hurry en route to Dunfermline City, with a train to catch. The first fill-up in a diesel Skoda Octavia after years of driving petrol is exactly the moment it happens. Your hand repeats what it has always done once you add rain, a phone call or a back seat full of children.
How to avoid petrol in a diesel at your next fill-up around Cairneyhill
- Check the petrol pump, not the colour. In the UK unleaded handles are usually green and diesel black, but not on each forecourt. The label is what counts.
- Inspect the filler flap. Many cars state the fuel inside the flap or on the cap. Look at it on your first fill in a vehicle you do not know.
- A coloured fob or a sticker on your diesel's key does more than any amount of meaning to remember, for a household with one of each.
- "Diesel", out loud, before you pick up the nozzle — every time a new or hired car needs its first tank. It seems silly. It works.
- Whilst you are thinking about something else, this is an easy mistake to make — so put the phone away.
- Up to a point, a misfuel inhibitor helps: some diesels come with a filler designed to block a petrol nozzle, and aftermarket devices are available for the remainder. Treat it as a safety net, and keep reading the pump.
- The moment you realise, stop: less petrol in that tank means a thinner blend. What to do next does not change, though — still do not crank it.
Cairneyhill: already put petrol in a diesel?
The order of things is short, then. Do not turn your ignition on, and do not fire it up. Ask the staff to help you roll it clear of the petrol pump if you are still on the forecourt, whether that is Thames Petroleum or somewhere else. What went in, about how much, and if it's run: tell us that when you ring 0333 366 0103.
Corrosion and deposits form the issue with AdBlue, where petrol brings lost lubrication. So if it was AdBlue, say so — and see its own Cairneyhill page.
One petrol in a diesel job around Cairneyhill costs more than another. Why?
The four situations above are four separate jobs, so no single quote for this would be honest. What shifts the cost is chiefly which of them you're in. Two things come after that: the petrol that got in as a proportion of what the tank holds, then the place the car is in and whether a technician can get to it safely.
What was put in, how much, and whether it's run — three questions our engineers ask before costing, not after, for exactly that reason. Given those answers, there is a straight figure instead of a range.
About Cairneyhill itself
Cairneyhill is a coastal village in Fife, situated near the city of Dunfermline and overlooking the Firth of Forth. Cairneyhill has a population of around 2323 people and is characterised by predominantly detached housing. Cairneyhill sits at an elevation of approximately 40 metres, close to nearby places such as Crombie, Crossford, and Torryburn.
Fuel drain cover across Fife, Cairneyhill included
Crombie, Crossford and Torryburn are among the places around Cairneyhill that the same vans work, answering petrol in diesel jobs across Cairneyhill's KY postcode area. Our engineers drain wherever the car is — your own drive, a lay-by, a supermarket car park, a forecourt — so it does not have to come to us.
Cairneyhill: still at the petrol pump?
No position is better: that is where you now are. Switched off it stays; then call.