Greystone: Petrol in a Diesel Car? How Worried to Be
Likely less than you are now — as long as nobody has started the vehicle. "Have I ruined it?" is the first thing anyone around Greystone asks, and the truthful answer is usually no, because petrol left in a diesel tank harms nothing till it's drawn through the system — by ignition priming, by your starter, or by being driven. To leave the car like that, call Petrol in Diesel and leave the engine alone. What petrol really does to a diesel, how to gauge how far it's travelled, and how to keep it from happening again: that's the remainder of this page.
Petrol in a diesel: what does it do to the motor?
Diesel has two tasks on its way through a motor. It burns, and before it ignites it lubricates. Extremely fine clearances are built into the fuel injectors and the high-pressure fuel pump, and just your diesel running through stops those surfaces grinding together.
The second task petrol doesn't do at all, and the first it does badly. Being less viscous than diesel, petrol strips out the lubrication a fuel system needs, so a pump running on that mixture wearing itself. It's also made to resist igniting under compression — the reverse of what a diesel needs — which is where you hear the knocking.
Put these together and the shape of the problem is clear. Contact doesn't do the harm — circulation does. A tank with petrol in it is a fuel fault. A pump that has been running on that petrol is the start of a mechanical one, and whatever a worn pump sheds moves on with the fuel to the fuel injectors downstream.
Four scenarios our technicians see around Greystone: how serious is petrol in a diesel?
Fuelled but never started — as good as it gets. Being on a forecourt is what makes this the case: elsewhere, the car has been driven there to begin with. With the petrol held inside that tank alone, it's emptied and flushed on the spot, and nothing more is needed.
Ignition on, or started for a second. Petrol has come out of that tank and got to the filter and your lines, since the system has been bled. Drain, flush, see to the filter: still usually simple.
Those few miles driven meant the pump working on fuel diluted by petrol throughout. How hard your car was driven matters as much as how far, and the work takes in that tank, the lines, the fuel filter and fresh fuel through the whole system. Driving the children to the local primary school is one sort of trip. A run as far as Carlisle, under 50 miles away, is a very different job. So is any distance on the A74(M), under 10 miles from Greystone, where the motor has been running hard the whole time.
Driven on until it protested — rattling, smoke, an uneven idle, a soft throttle. The engine is telling you your fuel is no longer behaving like diesel. Leave it where it stops: a lay-by, a side street, the verge on Marchmount Avenue. Permanent damage is very uncommon if a car is stopped soon, and the fuel drain and flush that still go first sort it out.
Stories Greystone people hear about petrol in a diesel
"Top it up the rest of the way with diesel and it'll be fine" — a myth. It won't. Nothing comes out when you top up — your tank simply holds more of the same mixture. A diesel fuel system doesn't accept petrol by percentage in the way that advice presumes.
"Newer diesels can handle a little petrol" — a myth, and nearer the reverse. At higher pressure, through finer components: that is how a current diesel handles its fuel, and so the lubrication matters more, not less.
The myth that catches people out: if it starts and drives, it must be unharmed. The driver of a petrol motor fed diesel normally has no choice but to stop, because it will not run, and the harm stops there. Feed petrol to a diesel and it usually starts, idles and pulls away as if nothing has happened — all while its pump wears. Running isn't the same as fine.
An outdated fix for a distinct problem is behind this one. Myth: "Add some two-stroke oil and drive the vehicle home." None of what petrol weakened gets put back by it — and later, the tank still contains the petrol.
The next start sends petrol back round the pump from the fuel lines and the fuel filter, where some of that sits after the motor has been run. That is why draining your tank yourself does not sort it — a myth. Also, a can of petrol drained by the kerbside is truly hazardous.
Why petrol in a diesel occurs so easily
It's rarely carelessness, and no one does it on purpose. A diesel nozzle generally won't fit a petrol car, yet the smaller petrol nozzle goes into the filler of a diesel almost without resistance — so forecourts make this one error easy, and just in that direction.
When routine and the car stop matching, it happens. A new car, a hire car or a courtesy car. Two vehicles on one drive, one petrol, one diesel. A forecourt you know, but with its pumps laid out differently. Rushing for a train outside Dumfries and filling up en route. The first fill-up in a diesel Volkswagen Tiguan after years of driving petrol is precisely the moment it takes place. With rain, a call coming in, or a car full of children to deal with, your hand simply does what it has always done.
Next time you fill up around Greystone: avoiding petrol in a diesel
- Not every forecourt in the UK follows green for unleaded and black for diesel, though most generally do. Read the pump's label; the colour is just a hint.
- In a vehicle you do not know, look inside the flap over the filler or at the cap before the first fill: plenty of vehicles state the fuel type there.
- One of each in the house? Mark the key to the diesel — a coloured fob, a sticker — because intending to remember is not enough.
- It seems daft and it does the trick: on your first fill in a new or hired car, say "diesel" aloud before you lift the nozzle off the petrol pump.
- Mistakes like this are simple to make whilst your mind is on something else, so your phone goes away.
- 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 cars without one. They are a backstop, not a reason to stop checking the pump.
- Stop as soon as you notice. Less petrol inside that tank means a thinner mixture. It does not change what to do next, which is still not to fire it up.
Petrol already in a diesel in Greystone? Begin here
Then the order of things is short. Do not switch your ignition on, and do not start it. Still at the forecourt, at Morrisons or anywhere else? Ask the attendants to help you roll the vehicle clear of the petrol pump. Then ring 0333 366 0103 and tell us what got in, roughly how much, and whether it has run.
Say so if it was AdBlue rather than petrol: it's a different problem, with its own page for Greystone, since AdBlue brings corrosion and deposits rather than lost lubrication.
Greystone petrol in a diesel tasks: why one costs more than another
A fair single quote doesn't exist here: four scenarios, four separate jobs. The scenario itself does most of the work of moving your cost. The proportion matters next, meaning how much of the tank is petrol, followed by the location of your car and whether reaching it is safe for our van.
Ahead of any quote, not after, come three questions: your fuel that was put in, its volume, and whether it has run. That's why. The replies change a range into a straight figure.
About Greystone
Greystone is a suburban area situated on the riverside in Dumfries and Galloway, with a relatively low elevation of 22 metres. Greystone lies near several smaller communities, including Marchmount, Greenbrae, and Stoop, and is located approximately 29 miles from Carlisle. Greystone has a population of around 3291 people, predominantly living in detached housing. Greystone is also relatively distant from major cities, with London being around 285 miles away.
Fuel drain cover in Greystone and across Dumfries and Galloway
The teams answering petrol in diesel calls around Greystone, in the DG postcode area, also work the spots around it, Marchmount, Greenbrae and Stoop included. A forecourt, a supermarket car park, a lay-by or your own drive are all places our engineers drain, and your car does not need to move to us.
In Greystone and still at the petrol pump?
Then you're in the best position there is. Switched off it stays; then phone.