Ludham: Petrol in a Diesel Car? How Worried to Be
Unstarted? Then less anxious than you probably are. Petrol resting in a diesel tank does nothing to the motor till something draws it through the system — the ignition priming the pump, the starter, or the drive on its own. So the honest answer to the first query everyone around Ludham asks, "have I wrecked it?", is normally no. To leave the vehicle like that, phone Petrol in Diesel and leave the engine alone. The rest of this page explains what petrol actually does to a diesel, how to tell how far it has got, and how to make sure it does not happen to you a second time.
The motor and petrol in a diesel: what goes on
Two tasks fall to diesel on its route round a motor. Before it ignites, it protects — then it combusts. What keeps the surfaces inside your high-pressure pump and the injectors from grinding against each other is your diesel flowing through them — they're built to extremely fine gaps.
Petrol handles the first job badly and the second not at all. A pump running on a petrol blend is wearing itself out, since petrol is thinner than diesel and takes away the protection the fuel system depends on. Petrol is also made to resist igniting under compression — the reverse of what a diesel wants from its fuel — and that is where the rattling starts.
Together, those leave the shape of the problem clear. Not contact but movement is what does the harm. Any tank with petrol in it is a fuel fault. A pump that has been working on that petrol is the start of a mechanical one, and whatever a worn pump sheds travels on with your fuel to your injectors further on.
Four scenarios we see in Ludham: how serious is petrol in a diesel?
Filled but not once started — as good as it gets. At a forecourt, and genuinely only there, the petrol is still confined to the tank — because anywhere else the vehicle was driven to reach it. The task is emptying and flushing on the spot.
Ignition on, or started for a second. Once primed, the system has drawn petrol out of that tank up to the fuel filter and your lines. That is generally still a simple job — a drain, a flush, and the filter dealt with.
Driven a couple of miles. Now your pump has spent those miles working on diluted fuel. Tank, lines, filter, then clean fuel run through the whole circuit: that is the work, and the way your car was driven matters as much as the miles. Driving the children to Ludham Primary School and Nursery is one kind of trip. Any miles on the M11, over 50 miles from Ludham, means your engine working hard throughout, and a run to Norwich, under 15 miles away, is a very different task as well.
It protested, and only then stopped: smoke, knocking, a throttle gone soft, an idle gone ragged. The fuel isn't acting like diesel any more, and your motor is telling you. Stop on the spot — on the verge on Yarmouth Road, at the kerb, down a side road — and don't move it again. A vehicle stopped quickly very rarely has lasting damage, because the fuel drain and the flush, which still go first, sort it out.
What Ludham people get told about petrol in a diesel — and the stories in it
"Top it up the rest of the way with diesel and it will be fine" — a myth. It won't. Nothing is removed by topping up — you're left with a fuller tank, still the same mixture. Percentage is not how a diesel fuel system copes with petrol, however much that guidance supposes.
Myth: "A current diesel can cope with a bit of petrol." If anything, the reverse. Lubrication matters more on modern diesels, not less, because their fuel runs through finer components at higher pressure.
This is the one that fools drivers. Myth: "If it starts and drives, there is no damage done." Feed diesel to a petrol engine and it usually will not run, and so the driver stops — and the harm stops with them. Feed petrol to a diesel and it usually starts, ticks over and pulls away like nothing has happened — all while its pump wears. Being able to run isn't proof of being fine.
An outdated fix for a different problem lies behind this one. Myth: "Add some two-stroke oil and drive it home." None of what petrol diluted is put back by it — and later, your tank still holds the petrol.
The next start sends petrol back round the pump from the lines and your filter, where some of that sits after the engine has run. That's why a DIY tank drain does not sort it — a myth. Besides, petrol emptied into a can by the road is truly hazardous.
How it happens: petrol in a diesel
A careless moment is rarely the cause, and nobody means to do it. The forecourt makes it easy: the petrol nozzle is the smaller of the two, and it slides into a diesel filler with almost no resistance, whilst a diesel nozzle generally will not go into a petrol car at all. So the error runs one way.
The moment habit stops matching your car is the moment it happens. Any car that is new to you — hired, on loan as a courtesy car, or just bought. One petrol and one diesel on the drive of the same household. A forecourt you know, only with its pumps arranged differently. A rushed fill on the way to Acle with a train to catch. Precisely the moment it occurs: after years of driving petrol, someone fills a diesel Renault Megane for the first time. The hand repeats what it has always done when you add rain, a phone call or a back seat full of children.
Next time you fill up in Ludham: avoiding petrol in a diesel
- Green for unleaded and black for diesel is normal in the UK — but not on each forecourt. Trust the label on the petrol pump, not the colour.
- Check the filler flap. Many cars state the fuel inside the flap or on the cap. Look at it on the first fill in any vehicle you do not know.
- Label the key. In a house with one of each, a coloured fob or a sticker on the diesel's key does more than any amount of intending to remember.
- Before the nozzle comes off the petrol pump the first time you fill a hired or new car, say "diesel" aloud. Silly, yes, yet it works.
- 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 built to block a petrol nozzle, and add-on devices are available for motors without one. They are a safety net, not a reason to stop checking the petrol pump.
- Less petrol makes a thinner mix, and so stop the moment you realise — though remembering that the next stage is unchanged. It's still not to start it.
Put petrol in a diesel around Ludham already?
Short and simple, then, is the order of things. Don't crank it, and do not switch the ignition on. Ask the attendants to help you roll it clear of the petrol pump if you're still on the forecourt, whether that's the nearest petrol station or somewhere else. Next, 0333 366 0103. We will ask what was put in, roughly how much, and if it's been run.
Say so if it was AdBlue instead of petrol: it's a different fault, with its own page for Ludham, because AdBlue brings corrosion and deposits rather than lost protection.
Ludham petrol in a diesel jobs: why one costs more than another
A fair single price doesn't exist here: four scenarios, four separate jobs. Chiefly, the cost shifts with which situation you're in. Next it's the ratio — how much petrol was put in against how much that tank holds — and after that where the car is and whether our van can get to it safely.
That's why our engineers ask three questions before quoting instead of after: what went in, how much, and whether it's run. The replies turn a range into a straight figure.
About Ludham and its setting
Ludham is a small village situated on the banks of the River Ant in Norfolk, with a low elevation of around 6 metres above sea level. Ludham lies near several other rural settlements, including High Mill Hill and Fritton, and is located approximately 11 miles from Norwich. Ludham has a population of around 718 people, predominantly living in detached houses. Ludham is also relatively distant from London, at a distance of around 109 miles.
Across Norfolk and in Ludham: fuel drain cover
Petrol in diesel call-outs in Ludham — part of the NR postcode area — go to teams that likewise cover the locations about it, High Mill Hill, Fritton and Johnson Street among them. Our engineers drain wherever your car is — your own driveway, a lay-by, a supermarket car park, a forecourt — so it never needs to come to us.
In Ludham and still at the petrol pump?
The best place there is, then — that is where you are. Switched off it remains; then phone.