Roman Hill: Petrol in a Diesel Car? How Worried to Be
Provided it hasn't been started, worry less than you probably are. Petrol resting in a diesel tank does nothing to your motor until something pulls it through the fuel system — the ignition priming your pump, your starter, or the drive on its own. So the honest answer to the first query anyone in Roman Hill asks, "have I wrecked it?", is normally no. To keep it like that, ring Petrol in Diesel then leave the motor alone. The remainder of this page sets out what petrol really does to a diesel, how to tell how far it has got, and how to make sure it doesn't happen to you again.
The motor and petrol in a diesel: what goes on
Two tasks fall to diesel on its journey round a motor. Lubricating comes before burning; it does both. Built to very fine gaps, the fuel injectors and your pump rely on the diesel moving through them to stop their surfaces wearing against one another.
The second task petrol does not do at all, and the first it does badly. The knocking 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 runnier than diesel, it strips out the protection the system hinges on, and any pump running on such a mixture is wearing itself.
Put these together and the shape of the issue is clear. It is circulation that does the damage, not contact. All a tank with petrol in it amounts to is a fuel problem. A pump that has been running on that petrol is the start of a mechanical one, and whatever a worn pump sheds travels on with your fuel to the injectors downstream.
Roman Hill, petrol in a diesel: four situations, from mild to serious
Fuelled up, not once started. The best case there is. That petrol is inside the tank and only the tank, and the job is a drain and a flush where the car sits. This is the one situation that can only truly occur on a forecourt, since anywhere else your car has been driven to get there.
A moment's running, or just the ignition on. Petrol has come out of your tank and reached the fuel filter and the lines, since your system has been primed. That's usually still an easy task — a drain, a flush, and the fuel filter dealt with.
A few miles driven, and the pump has spent each of them labouring on thinned fuel. How hard your car was driven counts as much as how far, and this work takes in your tank, the fuel lines, the filter and fresh fuel through the whole circuit. Driving the kids to Roman Hill Primary School is one sort of trip. A run as far as Norwich, under 25 miles away, is a very different job. So is any mileage on the M11, over 50 miles from Roman Hill, where the engine has been working hard the whole time.
Driven till it complained. Clattering, a ragged idle, smoke, a throttle that has gone soft. What you are hearing is the motor reporting fuel that no longer runs like diesel. Whether it's the verge on Raglan Street, a lay-by or a side street, stop where you are and leave it. A car pulled over quickly very rarely has permanent damage, because the drain and the flush, which still come first, take care of it.
What Roman Hill drivers get told about petrol in a diesel — and the stories in it
"Top it up the rest of the way with diesel and it'll be fine" — a myth. It won't. Topping up takes out nothing; it gives you a fuller tank of the same mix. Percentage is not how a diesel fuel system tolerates petrol, whatever that guidance presumes.
If anything, the reverse holds. Myth: "A current diesel can cope with a bit of petrol." A current diesel runs its fuel through smaller parts at higher pressure, which makes the lubrication count more, not less.
Myth: "If it starts and drives, there is no harm done." This is the one that catches people. Feed diesel to a petrol engine and it normally won't run, and so the motorist stops — and the harm stops with them. Feed petrol to a diesel and it usually starts, idles and drives away as if nothing happened — all while its pump wears. Running does not mean fine.
Myth: "Add some two-stroke oil and drive it home." It's an outdated fix for a different issue. None of what petrol diluted is put back by it — and afterwards, your tank still holds that petrol.
Myth: "Drain the tank yourself and you are sorted." Once your engine has run, some of that petrol is no longer inside your tank: it's in your filter and the fuel lines, and it goes straight back through your pump on your next start. Clearing petrol into a can by the roadside is also truly hazardous.
Petrol in a diesel: how does it occur?
Carelessness is seldom the cause, and nobody means to do it. The petrol nozzle is the slimmer of the two and slides into a diesel filler with almost no resistance; a diesel nozzle mostly will not go into a petrol car at all. The forecourt makes it easy, and the mistake runs one way.
The moment routine stops matching the vehicle is the moment it occurs. Courtesy car, hire car, or a vehicle that is new. A household with one petrol and one diesel on the driveway. The pumps in a different order on a familiar forecourt. Filling up in a hurry en route to Lowestoft, with a train to catch. Years of petrol motors behind you, a diesel Volkswagen Golf in front of you on the forecourt for its first tank — that's when. With rain, a call coming in, or children to deal with, your hand simply does what it always has.
How to prevent petrol in a diesel on your next fill-up in Roman Hill
- Green for unleaded and black for diesel is usual in the UK — but not on every forecourt. Trust the label on the petrol pump, not the colour.
- The first fill in a new car is the time to check your filler flap — on it, or on the cap, plenty of vehicles state which fuel to use.
- Good intentions do less than a sticker or a fob in a vivid colour on your diesel's key when a home has one of each. So mark it.
- "Diesel", out loud, before you pick up the nozzle — every time a new or hired car needs its first tank. It seems silly. It works.
- Whilst you are thinking about something else, this is an easy mistake to make — so tuck the phone away.
- A misfuel inhibitor helps, up to a point. Some diesels come with a filler built to reject a petrol nozzle, and add-on devices exist for vehicles without one. They are a safety net, not a reason to stop reading the pump.
- Stop as soon as you notice. Less petrol in that tank means a weaker blend. It does not change what to do next, which is still not to fire it up.
Put petrol in a diesel in Roman Hill already?
The order of things is brief, then. Don't turn the ignition on, and don't start it. Still at the forecourt, at Esso or anywhere else? Ask the staff to help you push it away from the pump. What was put in, roughly how much, and if it has run: tell us those when you call 0333 366 0103.
Corrosion and deposits form the trouble with AdBlue, whereas petrol means lost lubrication. So if it was AdBlue, say so — and see its own Roman Hill page.
Roman Hill petrol in a diesel tasks: why one costs more than another
There's no honest single price for this, because the four scenarios above are four separate jobs. Which of them you're in is mostly what moves the cost. The share counts next, meaning how much of the tank is petrol, followed by the location of the vehicle and whether reaching it is safe for a van.
Before any quote, not after, come three questions: the fuel that went in, the quantity, and if it's run. That is why. A range becomes a straight figure once those replies are in.
About Roman Hill itself
Roman Hill is a suburban area in Suffolk, situated near the coast and close to the towns of Lowestoft and Great Yarmouth. Roman Hill sits at a low elevation of around 9 metres, looking out towards the North Sea. Roman Hill is characterized by its predominantly terraced housing and forms part of the larger urban area surrounding Norwich and Lowestoft.
Roman Hill and Suffolk: where our fuel drain cover reaches
Roman Hill waits in the NR postcode area, and the teams that answer petrol in diesel call-outs there work the places around it as well — Lowestoft, Normanston and Gunton among them. The car does not need to move to us: we drain at a forecourt, in a supermarket car park, in a lay-by or on your own driveway.
Roman Hill: still at the pump?
The best position there is, then — that's where you are. Ring, and keep it switched off.