How Worried Should You Be? Petrol in a Diesel Car in Red Hall
Less than you probably are, provided it hasn't been started. "Have I ruined it?" is the first thing anyone around Red Hall asks, and the truthful answer is normally no, because petrol left in a diesel tank harms nothing until it's dragged through your fuel system — by ignition priming, by your starter, or by driving. Petrol in Diesel is who to call, with your engine kept off, and so it stays that way. The rest of this page explains what petrol really does to a diesel, how to tell how far it has got, and how to make sure it does not happen to you again.
Inside your engine: what petrol in a diesel really does
Two tasks fall to diesel on its route round a motor. Lubricating comes before burning; it does both. What stops the surfaces inside the high-pressure pump and the injectors from wearing down against one another is your diesel passing through them — they're made to extremely fine tolerances.
Petrol does the first task poorly and the second not at all. The rattling comes from petrol being designed not to ignite when compressed, which is precisely the reverse of what a diesel needs. On top of that it is thinner than diesel, it strips out the protection your system depends on, and any pump working on that mixture is wearing itself.
Taken together, they make clear the shape the issue takes. Contact doesn't do the damage — movement does. Petrol in a tank is a fuel problem. The start of a mechanical problem is a pump that has been running on that petrol — and whatever a worn pump sheds moves on with your fuel to your injectors beyond it.
How serious is petrol in a diesel? Four situations our technicians see in Red Hall
The best case there can be: filled up, not once started. The petrol is in the tank and only the tank, and the task is a drain and a flush where your car stands. This is the one scenario that can only really occur at a forecourt, since anywhere else the vehicle has been driven to get there.
Your ignition switched on, or a short start. With your system primed, the fuel lines and filter already contain petrol that has come from your tank. That is usually still a simple job — a drain, a flush, and the fuel filter seen to.
Some miles driven, and your pump has spent each of them working on diluted fuel. Tank, lines, filter, then fresh fuel run through the entire system: that's this work, and the way your car was driven matters as much as the miles. Short trips, like the school run to Red Hall Primary School, are one matter. Getting as far as Durham, under 25 miles away, makes a very different job — as does any miles on the A66(M), under 5 miles from Red Hall, with your engine labouring hard the whole time.
It complained, and only then stopped: smoke, rattling, a throttle gone soft, an idle gone lumpy. What you are hearing is the motor signalling fuel that no longer behaves like diesel. Leave it where it has stopped: a lay-by, a side street, the verge on Darlington Eastern Transport Corridor. Lasting damage is very unusual when a car is stopped soon, and the drain and flush that still go first deal with it.
What Red Hall people get told about petrol in a diesel — and the stories 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 fuller tank, still the same mix. That advice assumes a diesel fuel system handles petrol by percentage. It doesn't.
If anything, the reverse is true. Myth: "A modern diesel can cope with a bit of petrol." A newer diesel runs its fuel through smaller components at higher pressure, which makes the protection count more, not less.
"It starts, it drives, so there is no harm" — the myth that catches most drivers than any other. The motorist of a petrol motor fed diesel normally has no choice but to stop, since it will not run, and the damage stops there. Nothing looks to have happened when a diesel fed petrol fires up, ticks over and drives away, as it usually will; meanwhile your pump wears. Running doesn't mean fine.
Myth: "Add some two-stroke oil and drive the car home." It's an outdated fix for a separate fault. What petrol has thinned remains diluted, and the petrol remains inside that tank regardless.
Myth: "Drain that tank yourself and you are sorted." Once the engine has been run, some of that petrol is no longer in your tank: it is in the filter and the lines, and it goes right back through the pump on your next start. And, a can of petrol filled at the kerbside is genuinely dangerous.
Petrol in a diesel: how does it occur?
It's rarely carelessness, and no one does it on purpose. A diesel nozzle mostly will not 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.
Habit and your car getting out of step is when it occurs. A new motor, a hire car or a courtesy car. Two cars on one driveway, one petrol, one diesel. Your usual forecourt, its pumps suddenly in a different order. Fuelling up in a rush en route to Darlington, with a train to catch. The first fill-up in a diesel Volkswagen Tiguan after years of driving petrol is precisely the moment it happens. Add rain, a phone call or a back seat full of children, and your hand does what it has always done.
How to prevent petrol in a diesel on your next fill-up in Red Hall
- Not every forecourt in the UK follows green for unleaded and black for diesel, though most generally do. Check the petrol pump's label; the colour is just a hint.
- The first fill in a strange vehicle is the time to check the filler flap — on it, or on the cap, plenty of vehicles state the fuel to use.
- One of each in the household? Mark your key to the diesel — a coloured fob, a sticker — because meaning to remember isn't enough.
- It seems daft and it works: on the first fill in a new or hired car, say "diesel" out loud before you lift the nozzle off the pump.
- Mistakes like this are simple to make whilst your mind is on something else, so your phone goes away.
- Add-on devices exist for motors without one, and some diesels come with a filler that won't accept a petrol nozzle. Useful — but a backstop only, never a reason to stop checking the label.
- Noticing it halfway? Stop there and then. A thinner mix follows from less petrol inside your tank, yet your next stage remains the same: do not fire it up.
Red Hall: already put petrol in a diesel?
Short and simple, then, is the order of things. Don't start the vehicle, and do not switch the ignition on. If you are still on the forecourt — Shell or anywhere else — ask the attendants to help you push the vehicle away from the pump. Then call 0333 366 0103 and tell us what got in, about how much, and if it has run.
If it was AdBlue rather than petrol, say so. That's a separate fault — corrosion and deposits instead of lost lubrication — and it has its own page for Red Hall.
What makes one Red Hall petrol in a diesel job cost more than the next
Four separate jobs lie behind the four situations above — which is why there's no fair single quote. Mostly, your cost moves with which situation you're in. The share counts next, meaning how much of your tank is petrol, and then the location of the car and whether reaching it is safe for a van.
Ahead of any quote, not after, come three queries: your fuel that got in, the amount, and if it's run. That is why. A range becomes a straight figure when the answers are in.
About Red Hall
Red Hall is a suburban area located on the riverside in County Durham, with a mix of terraced housing and a population of around 2915 residents. Red Hall sits at an elevation of 51 metres, close to the nearby settlements of Haughton le Skerne and Great Burdon. Red Hall is situated near the city of Durham, which is approximately 17 miles away, and is part of the wider North East region. Red Hall is also within a reasonable distance from other nearby places, including Eastbourne.
Across Durham and in Red Hall: fuel drain cover
The vans answering petrol in diesel call-outs around Red Hall, in the DL postcode area, also work the locations near it, Haughton le Skerne, Great Burdon and Eastbourne included. You need not bring the vehicle to us. Forecourts, supermarket car parks, lay-bys and your own drive are all locations where we work.
In Red Hall and still at the petrol pump?
The best place there is, then — that is where you are. Turned off it stays; then ring.