Petrol in a Diesel Car in Finaghy: How Worried Should You Be?
Provided it has not been started, worry far less than you likely are. "Have I ruined it?" is the first question everyone in Finaghy asks, and the honest answer is usually no, since petrol left in a diesel tank harms nothing until it is dragged through your fuel system — by ignition priming, by the starter, or by driving. Leave the motor off and call Petrol in Diesel — that keeps it that way. Keep reading for three things: the effect petrol has inside a diesel engine, the signs of how far it has got, and the way to make sure you never repeat it.
What petrol in a diesel does to your engine
Passing through a motor, diesel does two jobs at once. Lubricating comes before burning; it does both. Very fine gaps go into the fuel injectors and the high-pressure pump, and just your diesel flowing through keeps their surfaces from grinding together.
Badly at the first, not at all at the second: that is petrol. A pump working on a petrol mix is wearing itself out, because petrol is runnier than diesel and strips out the lubrication the fuel system relies on. Petrol is also designed to resist igniting under compression — the reverse of what a diesel needs from its fuel — and that is where any knocking comes.
Combined, those leave the shape of the problem clear. Contact does not do the damage — circulation does. Petrol in the tank is a fuel fault. Once the pump has been running on that petrol, a mechanical problem has begun: anything shed by a pump that is wearing down is carried onward to your injectors with the fuel.
How bad is petrol in a diesel? Four situations our technicians see in Finaghy
Filled up, and not started: no case is better. Being on a forecourt is what makes this possible: elsewhere, your car has been driven there to begin with. With the petrol kept inside the tank alone, it's cleared and rinsed on the spot, and nothing more is needed.
Started for a moment, or only your ignition on. Once primed, your system has pulled petrol out of your tank as far as the fuel filter and the lines. Usually nothing more than draining, rinsing and sorting the fuel filter, and so still easy.
Driven a few miles. Now the pump has spent these miles running on thinned fuel. The work is your tank, your lines, the fuel filter and clean fuel through the whole system, and how hard your car was driven matters as much as how far. Short trips, like the school run to the local primary school, are one matter. Any mileage on the M77, over 50 miles from Finaghy, means the engine working hard throughout, and a run to Belfast, under 5 miles away, makes a very different job too.
Clattering, an uneven idle, smoke, a throttle gone soft: driven until it complained. What you are hearing is your engine reporting fuel that no longer runs like diesel. Whether it is the verge on South Crescent, a lay-by or a side street, stop where you are and leave it. Permanent damage is very uncommon when a vehicle is stopped quickly, and the fuel drain and flush that still come first deal with it.
Petrol in a diesel myths Finaghy people hear
"Top it up the rest of the way with diesel and it will be fine" — a myth. It will not. Nothing is removed when you top up — the tank just holds more of the same mixture. The assumption behind the advice — that diesel fuel systems tolerate petrol by percentage — is wrong.
If anything, the opposite is true. Myth: "A newer diesel can cope with a bit of petrol." Lubrication counts more on current diesels, not less, because their fuel runs through smaller components at higher pressure.
One myth that catches motorists out: if it starts and drives, it must be unharmed. Feed diesel to a petrol motor and it usually won't run, so the motorist stops — and the harm stops with them. Feed petrol to a diesel and it usually starts, ticks over and pulls away like nothing happened — all while its pump is wearing. Fine and running are not the same thing.
An old workaround for a different problem is behind this one. Myth: "Add some two-stroke oil and drive it home." None of what petrol thinned gets put back by it — and afterwards, that tank still holds the petrol.
Myth: "Drain your tank yourself and you're sorted." Once your engine has been run, some of the petrol is no longer inside that tank: it's in your filter and your lines, and it goes straight back through your pump on your next start. On top of that, petrol emptied into a can by the road is genuinely dangerous.
How it happens: petrol in a diesel
On purpose? Never. Through carelessness? Seldom, if ever. The petrol nozzle is the smaller of the two and slips into a diesel filler with almost no resistance; a diesel nozzle generally won't go into a petrol motor at all. The forecourt makes it simple, and the mistake runs one way.
The moment routine stops matching your car is the moment it takes place. Any car that is new to you — a hire car, on loan as a courtesy car, or brand new. Households running one of each, petrol and diesel. Your normal forecourt, its pumps suddenly in a different order. Fuelling up in a hurry en route to the nearest station, with a train to catch. Exactly the moment it happens: after years of driving petrol, someone fills a diesel Renault Megane for the first time. The hand does what it has always done once you add rain, a phone call or a back seat full of children.
Next time you fill up around Finaghy: preventing petrol in a diesel
- A green handle for unleaded and black for diesel is normal in the UK — yet not on every forecourt. Go by the label on the pump, not the colour.
- In a car you don't know, look inside the flap over your filler or at the cap before your first fill: plenty of cars print the fuel type there.
- One of each in the home? Mark the key to your diesel — a bright fob, a sticker — because meaning to remember is not enough.
- "Diesel", aloud, before you pick up the nozzle — each time a new or hired car needs its first tank. It sounds daft. It works.
- Tuck your phone away. This is an easy mistake to make whilst you're thinking about something else.
- A misfuel inhibitor helps, up to a point. Some diesels have a filler designed to reject a petrol nozzle, and add-on devices are available for vehicles without one. They are a safety net, not a reason to stop checking the petrol pump.
- As soon as you notice, stop: less petrol inside your tank makes a thinner mix. What to do next does not change, though — still do not crank it.
Petrol already in a diesel around Finaghy? Begin here
Short and simple, then, is the order of things. Do not switch your ignition on, and do not crank it. If you're still on the forecourt — the nearest petrol station or anywhere else — ask the staff to help you push the car away from the petrol pump. Call 0333 366 0103 next, with three facts — the fuel, the approximate amount, and if it has run.
AdBlue, not petrol? Then tell us. Corrosion and deposits, not lost protection, make it a different issue — Finaghy has a page just for it.
Finaghy petrol in a diesel jobs: why one costs more than another
A fair single quote doesn't exist here: four situations, four separate jobs. The scenario itself does most of the work of moving the cost. Where your car is matters too, and whether a van can safely reach it, after the share of petrol to what the tank takes.
Before any quote, not after, come three questions: your fuel that went in, the quantity, and if it's run. That's why. Given those replies, you get a straight figure rather than a range.
About Finaghy, for a moment
Finaghy is a locality situated inland in County Antrim, Northern Ireland, with an elevation of 28 metres above sea level. Finaghy lies approximately 3.2 miles from Belfast, near the surrounding areas of Dunmurry, Edenderry, and Drumbeg. Finaghy is characterised by its predominantly semi-detached housing stock, reflecting the residential nature of the area. Finaghy is home to around 3007 people, according to approximate population figures.
Finaghy and County Antrim: where our fuel drain cover runs
Finaghy rests in the BT postcode area, and the teams that answer petrol in diesel jobs there work the spots around it as well — Dunmurry, Edenderry and Drumbeg among them. A forecourt, a supermarket car park, a lay-by or your own driveway are all spots we drain, and the car does not need to move to us.
Still at the petrol pump around Finaghy?
The best spot there is, then — that's where you are. Phone, and leave it turned off.