Foulridge: Petrol in a Diesel Car? How Worried to Be
Unstarted? Then less worried than you likely feel. Petrol resting in a diesel tank does nothing to the motor till something pulls it through the system — your ignition priming your pump, your starter, or driving itself. So the truthful answer to the first query everyone in Foulridge asks, "have I ruined it?", is generally no. To leave it that way, ring Petrol in Diesel and leave your engine switched off. What petrol really does to a diesel, how to judge how far it has travelled, and how to stop it from happening again: that's the remainder of this page.
Petrol in a diesel: what does it do to your engine?
Two tasks fall to diesel on its journey round a motor. It burns, and before it combusts it lubricates. What stops the surfaces inside the high-pressure pump and your injectors from grinding against each other is your diesel flowing through them — they are designed to extremely fine clearances.
Of those two jobs, petrol manages the first badly and the second never. A pump running on a petrol mixture is wearing itself out, since petrol is runnier than diesel and strips out the protection your fuel system depends on. Petrol is also made to resist igniting under compression — the reverse of what a diesel wants from its fuel — and that is where the rattling comes.
Put those together and the shape of the issue is clear. The harm is done by movement, not by contact. Where that petrol is only inside that tank, it is a fault of fuel, nothing more. Whatever a worn pump sheds goes on, carried by your fuel, into your injectors downstream, which is why a pump that has worked on that petrol is where a mechanical fault starts.
Foulridge, petrol in a diesel: four situations, from mild to serious
The best case there can be: filled up, not once started. The petrol is inside the tank and only your tank, and the job is a drain and a flush where your car stands. This is the one scenario that can only truly take place at a forecourt, since anywhere else your car has been driven to get there.
A moment's running, or merely your ignition on. Once primed, the system has drawn petrol out of your tank up to the fuel filter and the lines. Drain, flush, see to the fuel filter: still usually simple.
A couple of miles driven, and the pump has spent every one of them running on weakened fuel. The work is that tank, the lines, the filter and fresh fuel through the whole circuit, and how hard your car was driven counts as much as how far. On the school run to Foulridge Saint Michael and All Angels CofE Voluntary Aided Primary School, the miles is short. Very different once more: a trip to Bradford, under 25 miles away, or some distance on the M65, under 3 miles from Foulridge, where your engine kept running hard.
It protested, and only then stopped: smoke, rattling, a throttle gone soft, an idle gone uneven. What you are hearing is the motor signalling fuel that no longer acts like diesel. Stop wherever you are — the verge on Causeway, a lay-by, a side street — and leave it there. A car pulled over soon very seldom has long-term damage, as the drain and the flush, which still go first, take care of it.
What Foulridge people get told about petrol in a diesel — and the myths in it
Myth: "Fill it the rest of the way with diesel and it will be fine." It will not. Nothing is removed by topping up — you're left with a bigger tank, still the same mixture. The assumption behind the guidance — that diesel fuel systems tolerate petrol by percentage — is wrong.
Myth: "A newer diesel can cope with a bit of petrol." If anything, the reverse. A current diesel runs its fuel through more precise parts at higher pressure, which makes the lubrication count more, not less.
The myth that catches drivers out: if it starts and drives, it must be unharmed. The driver of a petrol motor fed diesel normally stops, because it will not run, and the harm stops with them. A diesel fed petrol normally starts, ticks over and drives away as if nothing has happened, while your pump grinds. Fine and running aren't the same at all.
Myth: "Add some two-stroke oil and drive it home." It is an outdated fix for a separate issue. None of what petrol weakened gets put back by it — and later, that tank still holds the petrol.
Once the engine has been run, part of that petrol is in the filter and the lines, not that tank — and your next start sends it straight back through your pump. So the myth "drain the tank yourself and you're sorted" does not hold. It's also genuinely hazardous to drain petrol into a can at the roadside.
Petrol in a diesel: how does it occur?
Nobody does it on purpose, and it is rarely carelessness. The forecourt makes it simple: the petrol nozzle is the smaller of the two, and it slides into a diesel filler with almost no resistance, while a diesel nozzle generally will not go into a petrol car at all. So the mistake runs one way.
It takes place when habit and your car stop matching. A new vehicle, a hire car or a courtesy car. A household with one petrol and one diesel on the driveway. Your normal forecourt, its pumps now in a different order. Fuelling up in a hurry en route to Colne, with a train to catch. Years of petrol vehicles behind you, a diesel Volkswagen Golf in front of you at the forecourt for its first tank — that is when. With rain, a call coming in, or a car full of children to deal with, the hand simply does what it has always done.
Next time you fill up around Foulridge: avoiding petrol in a diesel
- A green handle for unleaded and black for diesel is usual in the UK — yet not on each forecourt. Go by the label on the pump, not the colour.
- Check your filler flap. Many vehicles state the fuel inside the flap or on the cap. Look at it on the first fill in a car you don't know.
- One of each in the home? Mark the key to the diesel — a bright fob, a sticker — since intending to remember is not enough.
- "Diesel", aloud, before you lift the nozzle — each time a new or hired car gets its first tank. It seems silly. It works.
- Mistakes like this are simple to make while your mind is on something else, so your phone goes away.
- Some diesels have a filler designed to refuse a petrol nozzle, and devices you can add are available for vehicles without one. Such an inhibitor helps up to a point — as a safety net, not a reason to stop checking the pump.
- Noticing it mid-fill? Stop at once. A thinner mixture follows from less petrol in that tank, yet your next stage stays the same: don't fire it up.
Foulridge: already put petrol in a diesel?
Short and simple, then, is the order of things. Do not switch the ignition on, and do not crank it. Still on the forecourt, at Sainsbury's or anywhere else? Ask the attendants to help you roll it away from the pump. Then ring 0333 366 0103 and tell us what was put in, roughly how much, and if it has run.
If it was AdBlue and not petrol, say so. That's a different problem — corrosion and deposits rather than lost lubrication — and it has its own page for Foulridge.
One petrol in a diesel task in Foulridge costs more than another. Why?
The four situations above are four separate tasks, so no single quote for this would be fair. What moves your cost is mostly which of them you are in. Two things follow that: the petrol that got in as a proportion of what the tank holds, then the spot the vehicle is in and whether a technician can reach it safely.
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 answers, there is a straight figure instead of a range.
About Foulridge
Foulridge is a village situated on the shores of a lake in Lancashire, with a mix of terraced housing and other residential properties. Foulridge sits at an elevation of 174 metres, near the towns of Colne and Nelson, and is surrounded by the Pennine countryside. Foulridge is located near the villages of Colne Edge and Hey, and is approximately 17.9 miles from Bradford. Foulridge has a population of around 1556 people, according to recent estimates.
Across Lancashire and around Foulridge: fuel drain cover
Colne Edge, Hey and Colne are among the spots near Foulridge that the same teams work, answering petrol in diesel calls across Foulridge's BB postcode area. Our engineers drain wherever the vehicle is — your own driveway, a lay-by, a supermarket car park, a forecourt — so it does not have to come to us.
Foulridge: still at the petrol pump?
Nothing beats it: that is where you are. Keep it off. Call.