Petrol in a Diesel Car in Liss: How Worried Should You Be?
Unstarted? Then less worried than you probably feel. Everyone in Liss begins with "have I ruined it?", and the honest answer is usually no: petrol left inside that tank of a diesel stays harmless till priming, cranking or driving draws it into the system. Leave the motor off and call Petrol in Diesel — that keeps it like that. What petrol really does to a diesel, how to gauge how far it has travelled, and how to keep it from happening again: that's the rest of this page.
The motor and petrol in a diesel: what happens
On its way through a motor, diesel has two tasks. It lubricates to begin with, and after that does it burn. What keeps the surfaces inside the high-pressure pump and the injectors from grinding against each other is the diesel passing through them — they are made to very fine gaps.
Badly at the first, not at all at the second: that's petrol. It is thinner than diesel and removes the protection the system depends on, and so a pump running on a petrol blend is a pump wearing itself. And petrol is made to resist igniting under compression, which is the reverse of what a diesel needs from its fuel. That's where the knocking comes from.
The shape of the problem is plain when you put those together. Contact does not do the harm — movement does. A tank with petrol in it is a fuel fault. The start of a mechanical one is a pump that has been labouring on that petrol — and whatever a worn pump sheds moves on with your fuel to the injectors downstream.
Four situations our engineers see in Liss: how bad is petrol in a diesel?
Filled up, and never started: no case is better. The petrol is inside the tank and only your tank, and the task is a drain and a flush where the vehicle sits. This is the one situation that can only really happen on a forecourt, since anywhere else the vehicle has been driven to get there.
A moment's running, or merely your ignition on. With the system primed, your lines and filter already contain petrol that came from your tank. That is generally still a simple job — a drain, a flush, and the filter seen to.
Those few miles on the road meant your pump labouring on fuel weakened by petrol throughout. Mileage is only half of it; how hard it was driven counts just as much. Either way this work includes the tank, the fuel lines, your filter and clean fuel through the entire circuit. Driving the children to Liss Junior School is one kind of trip. A run as far as Chichester, under 25 miles away, is a very different task. So is any mileage on the Waterlooville Bypass, under 10 miles from Liss, where the engine has been labouring hard the whole time.
Driven until it protested. Knocking, an uneven idle, smoke, a throttle that has gone soft. That is the motor telling you its fuel no longer is behaving like diesel. Whether it is the verge on Mill Road, a lay-by or a side street, stop where you are and leave it. A car stopped early very seldom has long-term damage, since the drain and the flush-through, which still come first, take care of it.
What Liss motorists get told about petrol in a diesel — and the stories in it
It will not be fine. The myth: "Fill it the rest of the way with diesel and it'll be." Topping up takes out nothing; it gives you a fuller tank of the same mixture. The assumption behind that guidance — that diesel fuel systems tolerate petrol by percentage — is wrong.
"Modern diesels can handle a little petrol" — a myth, and closer to the opposite. At higher pressure, through smaller components: that's how a current diesel moves its fuel, and so the protection counts more, not less.
This is the one that catches people. Myth: "If it starts and drives, there is no harm done." Feed diesel to a petrol engine and it generally will not run, and so the motorist stops — and the damage stops with them. Nothing seems to have happened when a diesel fed petrol fires up, ticks over and drives away, as it usually does; meanwhile your pump wears. Fine and running are not the same thing.
An old workaround for a separate issue is behind this one. Myth: "Add some two-stroke oil and drive the vehicle home." None of what petrol weakened is put back by it — and later, the tank still holds the petrol.
The next start sends petrol back round the pump out of your lines and your filter, where some of that ends up once your engine has run. That is why a DIY tank drain does not sort it — a myth. On top of that, petrol drained into a can by the road is genuinely risky.
How it happens: petrol in a diesel
No one does it on purpose, and it is seldom carelessness. One way only, because of the nozzles: the slimmer petrol one slides inside a diesel filler with almost no resistance, whereas the diesel one mostly won't fit a petrol motor. That is how the forecourt makes it easy.
Habit and the vehicle getting out of step is when it occurs. A car that is new to you — hired, on loan as a courtesy car, or just bought. One petrol and one diesel on the driveway of the same household. A forecourt you know, only with its pumps arranged differently. Rushing for a train outside the nearest station and fuelling up en route. Exactly the moment it takes place: after years of driving petrol, a driver fills a diesel Volkswagen Passat for the first time. With rain, a call coming in, or a car full of children to deal with, your hand simply does what it has always done.
Preventing petrol in a diesel next time you fill up in Liss
- Green for unleaded and black for diesel is normal in the UK — yet not on each forecourt. Go by the label on the pump, not the colour.
- The first fill in a new car is the time to check your filler flap — inside it, or on the cap, plenty of cars state the fuel to use.
- Mark the key. In a household with one of each, a coloured fob or a sticker on your diesel's key does more than any amount of meaning to remember.
- Before the nozzle leaves the petrol pump the first time you fill a hired or new car, say "diesel" aloud. Daft, perhaps, yet it works.
- Mistakes like this are easy to make while your mind is on something else, so your phone goes away.
- Some diesels come with a filler built 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 reading the petrol pump.
- Spotting it mid-fill? Stop there and then. A thinner mix follows from less petrol inside the tank, but your next stage remains the same: do not crank it.
Already put petrol in a diesel around Liss?
Then the order of things is short. Leave it unstarted, with your ignition off too. Yet at the forecourt, at Esso or anywhere else? Ask the attendants to help you push it away from the pump. Then call 0333 366 0103 and tell us what got in, about how much, and whether it has run.
AdBlue, not petrol? Then tell us. Corrosion and deposits, not lost lubrication, make it a different fault — Liss has a page all for it.
One petrol in a diesel job around Liss costs more than another. Why?
Four different jobs lie behind the four situations above — which is why there's no honest single price. What moves your cost is mostly which of them you are in. Where the vehicle is matters too, and whether a technician can safely get to it, after the share of petrol to what that tank takes.
What was put in, how much, and if it's run — three questions our technicians ask before pricing, not after, for exactly that reason. Given those replies, there is a straight figure rather than a range.
About Liss and its setting
Liss is a village in Hampshire, situated on the banks of the River Rother at an elevation of 66 metres. Liss has a mix of housing types, but semi-detached homes are predominant, and the village is surrounded by nearby places such as Lower Green, East Hill, and Princes Marsh. Liss is located near the city of Chichester, approximately 15 miles away, and is about 46 miles from London. Liss remains a small community with a population of around 2654 residents.
Liss and Hampshire: where our fuel drain cover runs
Lower Green, East Hill and Princes Marsh are among the locations around Liss that the same teams work, answering petrol in diesel jobs across Liss's GU postcode area. Our engineers drain wherever your vehicle is — your own drive, a lay-by, a supermarket car park, a forecourt — so it does not have to come to us.
At the petrol pump around Liss, right now?
Nothing beats it: that is where you are. Turned off it stays; then call.