Currie: Petrol in a Diesel Car? How Worried to Be
Unstarted? Then less anxious than you probably are. Everyone in Currie starts with "have I wrecked it?", and the honest answer is normally no: petrol left inside that tank of a diesel remains harmless till priming, cranking or driving draws it into the fuel system. Keep it that way: leave your engine off then ring Petrol in Diesel. What petrol really 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 remainder of this page.
Inside the engine: what petrol in a diesel really does
Two jobs fall to diesel on its journey through a motor. Before it combusts, it lubricates — and then it ignites. Your high-pressure pump and the injectors are designed to extremely fine gaps, and your diesel passing through them is what stops those surfaces from wearing against one another.
The second job petrol does not do at all, and the first it does poorly. A pump running on a petrol mixture is wearing itself out, because petrol is runnier than diesel and takes away the lubrication the fuel system depends on. Petrol is also made to resist igniting under compression — the opposite of what a diesel wants from its fuel — and that's where the knocking comes.
Put those together and the shape of the issue is clear. Not contact but circulation is what causes the harm. Where the petrol is only in that tank, it is a problem of fuel, nothing more. Whatever a worn pump sheds goes on, borne by your fuel, into your injectors downstream, which is why a pump that has been working on the petrol is where a mechanical problem begins.
How bad is petrol in a diesel? Four scenarios our technicians see around Currie
Filled up, not once started. The best case there is. The petrol is in the tank and only the tank, and the job is a drain and a flush where the vehicle sits. This is the one situation that can only truly occur on a forecourt, since anywhere else the car has been driven to get there.
Ignition on, or started for a moment. Petrol has left that tank and got to the filter and the lines, since the system has been bled. Drain, flush, see to your filter: still normally simple.
Those few miles driven were the pump working on fuel diluted by petrol the whole way. The work is that tank, the lines, the fuel filter and clean fuel through the whole circuit, and how hard your car was driven matters as much as how far. On the school run to the local primary school, the miles is small. A run as far as Edinburgh, under 10 miles away, is a very different task. So is any mileage on the M8, under 3 miles from Currie, where the motor has been working hard the whole time.
Driven on until it complained — knocking, smoke, a lumpy idle, a soft throttle. That's the motor telling you its fuel has stopped acting like diesel. Pull up wherever you are — the verge on Curriehill Road, a lay-by, a side street — and leave it where it is. The fuel drain and flush-through still go first, and they deal with it: if a vehicle is stopped quickly, long-term damage is very uncommon.
Currie drivers and that petrol in a diesel myths they hear
"Top it up the rest of the way with diesel and it will be fine" — a myth. It will not. Nothing comes out when you top up — your tank simply carries more of the same mixture. That advice assumes a diesel fuel system handles petrol by percentage. It does not.
"Modern diesels can handle a little petrol" — a myth, and closer to the opposite. More precise parts and higher pressure are how a current diesel runs its fuel, and that makes the lubrication matter more, not less.
Myth: "If it starts and drives, there is no harm done." This is the one that catches drivers. The motorist of a petrol engine fed diesel usually has no choice but to stop, since it will not run, and the harm stops with them. A diesel fed petrol usually starts, idles and drives away as if nothing has happened, whilst the pump grinds. Running is not the same as fine.
Myth: a two-stroke additive lets you to drive home. It was an old fix, supposed for another fault. What petrol has diluted stays thinned, and that petrol remains in your tank anyway.
"Drain it yourself and you're sorted" — a myth, because after it has been running some petrol lies in the filter and lines, ready to go right back through the pump on your next start. Also, a can of petrol drained at the roadside is genuinely dangerous.
How does petrol in a diesel take place?
No one does it on purpose, and it is rarely carelessness. The petrol nozzle is the smaller of the two and slips into a diesel filler with almost no resistance; a diesel nozzle mostly won't go into a petrol vehicle at all. The forecourt makes it easy, and the slip runs one way.
It takes place when routine and the car stop matching. A car that is new to you — hired, on loan as a courtesy car, or brand new. Two vehicles on one drive, one petrol, one diesel. The pumps in a different order on a well-known forecourt. Rushing for a train at Curriehill and filling up en route. The first fill-up in a diesel Volkswagen Golf after years of driving petrol is exactly the moment it happens. 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 in Currie: preventing petrol in a diesel
- Read the petrol pump, not the colour. In the UK unleaded handles are normally green and diesel black, yet not on each forecourt. The label is what counts.
- Check the filler flap. Many vehicles state the fuel type inside the flap or on the cap. Look at it on your first fill in any vehicle you do not know.
- Good intentions count for less than a sticker or a fob in a bright colour on your diesel's key when a household has one of each. So label it.
- Say it before you lift it. On your first fill in a new or hired car, say "diesel" aloud before you lift the nozzle off the pump. It seems daft and it does the trick.
- Mistakes like this are straightforward to make whilst your mind is on something else, and so the phone goes away.
- 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 vehicles without one. They are a backstop, not a reason to stop reading the petrol pump.
- Spotting it mid-fill? Stop there and then. A thinner mix follows from less petrol inside that tank, yet the next step remains the same: don't crank it.
Petrol already in a diesel in Currie? Begin here
Then the order of things is short. Do not switch the ignition on, and do not crank it. Yet on the forecourt, at Sainsbury's or anywhere else? Ask the attendants to help you roll it away from the pump. What was put in, roughly how much, and whether it's run: tell us that when you call 0333 366 0103.
If it was AdBlue and not petrol, say so. That is a separate issue — corrosion and deposits rather than lost protection — and it has its own page for Currie.
One petrol in a diesel task around Currie costs more than another. Why?
Four separate tasks lie behind the four scenarios above — which is why there's no fair single price. What moves the cost is mostly which of them you are in. Where your car is counts too, and whether our van can safely reach it, after the ratio of petrol to what that tank takes.
Ahead of any quote, not after, we ask three questions: your fuel that was put in, its volume, and if it has run. That's why. Their replies are what turn a range into one firm number.
About Currie and where it is
Currie is a suburban area in the City of Edinburgh, situated near the Water of Leith and overlooking the surrounding countryside. Currie sits at an elevation of 136 metres, approximately 6 miles west of Edinburgh's city centre. Currie has a mix of housing types, but semi-detached homes are particularly prevalent in the area. Currie is close to nearby places such as Riccarton and Gowanhill, making it a connected residential community.
Fuel drain cover across City of Edinburgh, Currie included
Our vans answering petrol in diesel call-outs around Currie, in the EH postcode area, also work the locations around it, Riccarton, Gowanhill and Warriston among them. You need not bring the car to us. Forecourts, supermarket car parks, lay-bys and your own drive are all locations we drain.
Still at the petrol pump in Currie?
Nothing beats it: that's where you now are. Turned off it stays; then call.