Holmhead: Petrol in a Diesel Car? How Worried to Be
Far less than you likely are, provided it has not been started. Until the ignition primes your pump, your starter cranks, or the car is driven, petrol in a diesel tank simply waits there and does no harm. Which makes the truthful reply to that first Holmhead question — "have I ruined it?" — normally no. To leave the car that way, ring Petrol in Diesel and leave your motor switched off. What petrol actually does to a diesel, how to gauge how far it has travelled, and how to stop it from happening a second time: that's the rest of this page.
Your engine and petrol in a diesel: what happens
Diesel does two jobs on its way through a motor. Before it burns, it protects — and then it ignites. What keeps the surfaces inside the high-pressure fuel pump and the fuel injectors from wearing against each other is the diesel passing through them — they're built to extremely fine tolerances.
Badly at the first, not at all at the second: that is petrol. The clattering comes from petrol being made not to ignite when compressed, which is precisely the opposite of what a diesel needs. On top of that it is thinner than diesel, it strips out the protection the system depends on, and any pump running on that blend is wearing itself.
Taken together, they make clear what shape the problem has. Contact does not do the damage — movement does. All a tank with petrol in it amounts to is a fuel issue. The start of a mechanical one is a pump that has been running on that petrol — and whatever a worn pump sheds moves on with the fuel to the injectors beyond it.
Petrol in a diesel around Holmhead: how serious is it? Four situations
Fuelled up, never started. The best case there can be. Just your tank has petrol in it, so the task is clearing the tank and flushing the fuel system where the vehicle sits. This scenario can only truly take place on a forecourt: anywhere else, the car got there by being driven.
A moment's running, or just the ignition on. With the fuel system primed, your lines and filter already contain petrol that came from your tank. Drain, flush, deal with the filter: still usually simple.
Those few miles driven meant your pump working on fuel diluted by petrol throughout. The work is that tank, the fuel lines, the fuel filter and clean fuel through the entire circuit, and how hard the car was driven matters as much as how far. Short trips, like the school run to the local primary school, are one matter. A run as far as Glasgow, under 50 miles away, is a very different task. So is any mileage on the M77, under 25 miles from Holmhead, where your engine has been labouring hard the whole time.
Knocking, an uneven idle, smoke, a throttle gone soft: driven until it complained. The engine is telling you your fuel is no longer behaving like diesel. Stop wherever you are — the verge on Auchinleck Road, a lay-by, a side street — then leave it there. Permanent damage is very rare if a car is pulled over quickly, and the drain and flush that still come first sort it out.
Stories Holmhead motorists hear about petrol in a diesel
"Top it up the rest of the way with diesel and it will be fine" — a myth. It will not. Nothing is removed by topping up — you're left with a bigger tank, still the same mixture. Percentage isn't how a diesel fuel system copes with petrol, however much that advice supposes.
Not so: a modern diesel copes with a bit of petrol. If anything, the reverse. At higher pressure, through more precise parts: that is how a current diesel moves its fuel, so the protection matters for more, not less.
This is the one that catches people. Myth: "If it starts and drives, there's no damage done." Diesel in a petrol motor generally leaves a motor that will not run: the driver stops, and so does the harm. Feed petrol to a diesel and it usually fires up, ticks over and drives away like nothing happened — all while its pump wears. Fine and running are not the same at all.
Myth: a two-stroke additive lets you to drive home. It is an old fix, supposed for another fault. It does not put back what petrol has thinned, and that petrol is still in the tank later on.
"Drain it yourself and you're sorted" — a myth, since after it's been running some petrol lies in your filter and lines, waiting to go straight back through the pump at the next start. On top of that, petrol drained into a can by the road is genuinely risky.
How does petrol in a diesel take place?
It is rarely carelessness, and nobody does it on purpose. The petrol nozzle is the smaller of the two and slides into a diesel filler with almost no resistance; a diesel nozzle generally won't go into a petrol vehicle at all. The forecourt makes it easy, and the slip runs one way.
Routine and the vehicle getting out of step is when it happens. Courtesy car, hire car, or a motor that is brand new. Two cars on one drive, one petrol, one diesel. A forecourt you know, only with its pumps arranged differently. Racing for a train at Auchinleck and fuelling up en route. Exactly the moment it occurs: after years of driving petrol, a driver fills a diesel Volkswagen Golf for the first time. Add rain, a phone call or a back seat full of kids, and your hand repeats what it has always done.
Preventing petrol in a diesel next time you fill up around Holmhead
- Green for unleaded and black for diesel is usual in the UK — yet not on each forecourt. Trust the label on the petrol pump, not the colour.
- Many motors state the fuel inside the filler flap or on the cap, so check it on the first fill in a car you do not know.
- One of each in the home? Label your key to your diesel — a bright 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" aloud before you lift the nozzle off the petrol pump.
- Put your phone away. This is an easy mistake to make whilst you are thinking about something else.
- A misfuel inhibitor helps, up to a point. Some diesels have a filler designed to refuse a petrol nozzle, and add-on devices are available for cars without one. They are a backstop, not a reason to stop checking the petrol pump.
- Noticing it mid-fill? Stop at once. A thinner mixture results from less petrol inside the tank, yet your next step remains the same: do not crank it.
Petrol already in a diesel in Holmhead? Start here
Then, there is only a short order of things. Starting it is out, and so is switching on the ignition. If you are still at the forecourt — the nearest petrol station or anywhere else — ask the staff to help you roll the vehicle clear of the pump. Phone 0333 366 0103 next, with three answers — your fuel, the approximate amount, and whether it's run.
If it was AdBlue and not petrol, say so. That is a different fault — corrosion and deposits and not lost lubrication — and it has its own page for Holmhead.
One petrol in a diesel job around Holmhead costs more than another. Why?
The four scenarios above are four separate jobs, so no single quote for this would be fair. The scenario itself does most of the work of moving your cost. Where your car is matters too, and whether a technician can safely reach it, after the proportion of petrol to what that tank holds.
That's why our technicians ask three queries before quoting rather than after: what went in, how much, and if it has run. Given the answers, you get a straight figure instead of a range.
About Holmhead
Holmhead is a suburban area situated on the riverside in East Ayrshire, with a mix of detached housing and a relatively small population of around 2165 residents. Holmhead sits at an elevation of 116 metres, near the communities of Knockroon and Cumnock, and is located approximately 28 miles from Glasgow. Holmhead is part of the wider residential area surrounding the town of Cumnock, with The Rigg nearby. Holmhead's location in southern Scotland puts it around 322 miles northwest of London.
Across East Ayrshire and in Holmhead: fuel drain cover
The teams answering petrol in diesel calls around Holmhead, in the KA postcode area, equally work the locations near it, Knockroon, Cumnock and The Rigg included. You need not move your car to us. Forecourts, supermarket car parks, lay-bys and your own driveway are all locations we drain.
At the petrol pump in Holmhead, right now?
In that case, you couldn't be in a better spot. Turned off it stays; then phone.