Coldean: Petrol in a Diesel Car? How Worried to Be
Less than you probably are, if it hasn't been started. Petrol resting in a diesel tank does nothing to the motor till something pulls it through the system — the ignition priming your pump, your starter, or driving itself. So the truthful answer to the first query anyone in Coldean asks, "have I ruined it?", is normally no. Petrol in Diesel is who to phone, with the motor left off, and so it stays that way. The remainder of this page covers what petrol really does to a diesel, how to judge how far it has got, and how to make sure it does not happen to you again.
Petrol in a diesel: what does it do to the engine?
Passing through a motor, diesel is doing two things at once. Lubricating comes before burning; it does both. Your high-pressure pump and the fuel injectors are designed to extremely fine gaps, and your diesel passing through them is what stops those surfaces from wearing down against each other.
Poorly at the first, not at all at the second: that's petrol. It's thinner than diesel and removes the lubrication the fuel system depends on, and so a pump running on a petrol blend is a pump wearing itself. And petrol is designed to resist igniting under compression, which is the opposite of what a diesel needs from its fuel. That is where the rattling comes from.
Put those together and the shape of the problem is clear. Contact does not do the harm — movement does. Petrol in a tank is a fuel problem. The start of a mechanical one is a pump that has been labouring on that petrol — and whatever a worn pump sheds travels on with your fuel to your injectors downstream.
Coldean, petrol in a diesel: four cases, from mild to significant
The best case there can be: filled up, never started. On a forecourt, and genuinely only there, the petrol is still limited to your tank — since anywhere else the vehicle was driven to reach it. The job is draining and flushing on the spot.
Started for a second, or just the ignition on. The fuel system has been primed, and so petrol has left that tank and got to the filter and the fuel lines. That's normally still an easy job — a drain, a flush, and your filter dealt with.
A couple of miles driven, and the pump has spent every one of them running on diluted fuel. Miles is only half of that; how hard it was driven matters just as much. Either way the work includes the tank, the fuel lines, the filter and fresh fuel through the entire system. Driving the children to Coldean Primary School is one sort of trip. Any distance on the M23, under 25 miles from Coldean, means the motor has worked hard throughout, and a run to Brighton and Hove, under 5 miles away, is a very different job as well.
Clattering, a ragged idle, smoke, a throttle gone soft: driven until it complained. What you are hearing is the engine signalling fuel that no longer runs like diesel. Pull up on the spot — on the verge on Coldean Lane, at the kerb, down a side road — and don't move it again. Permanent damage is very rare when a car is stopped early, and the fuel drain and flush-through that still come first deal with it.
Coldean people and that petrol in a diesel stories they hear
It will not be fine. The myth: "Fill it the rest of the way with diesel and it'll be." Nothing comes out when you top up — the tank simply holds more of the same mixture. A diesel fuel system does not accept petrol by percentage in the way that guidance supposes.
"Modern diesels can handle a little petrol" — a myth, and nearer the reverse. Lubrication matters more on current diesels, not less, because their fuel passes through more precise parts at higher pressure.
This is the one that fools drivers. Myth: "If it starts and drives, there's no harm done." Feed diesel to a petrol engine and it usually will not run, so the motorist stops — and the harm stops with them. Feed petrol to a diesel and it normally fires up, idles and pulls away as if nothing happened — all the while its pump wears. Running does not mean fine.
Not so: a two-stroke additive lets you to drive home. It was an old workaround, supposed for another fault. That petrol is still inside the tank afterwards, and whatever it has weakened isn't put back.
Myth: "Drain the tank yourself and you're sorted." After the engine has run, some of the petrol is no longer in that tank: it is in the filter and your lines, and it goes right back through the pump on your next start. It's also really risky to drain petrol into a can by the roadside.
Petrol in a diesel: how does it take place?
It is seldom carelessness, and no one does it on purpose. The forecourt makes it easy: the petrol nozzle is the slimmer 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 motor at all. So the slip runs one way.
It occurs when routine and your car stop matching. A new car, a hire car or a courtesy car. One petrol and one diesel on the drive of the same household. A forecourt you know, only with its pumps arranged differently. Rushing for a train at Falmer and fuelling up en route. A new-to-you diesel Volkswagen Golf, its first fuelling, and a driver used to petrol: exactly when it happens. Add rain, a phone call or a back seat full of kids, and the hand repeats what it has always done.
Preventing petrol in a diesel next time you fill up around Coldean
- Not every forecourt in the UK keeps to green for unleaded and black for diesel, though most generally do. Check the petrol pump's label; the colour is just a clue.
- In a motor you don't know, look inside the flap over the filler or at the cap before your first fill: many motors print the fuel type there.
- Mark your 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 pump the first time you fill a hired or new car, say "diesel" aloud. Silly, yes, yet it does the trick.
- Put the phone away. This is an easy mistake to make whilst you're thinking about something else.
- Some diesels come with a filler built to block a petrol nozzle, and devices you can add are available for vehicles without one. Such an inhibitor helps up to a point — as a backstop, not a reason to stop reading the petrol pump.
- Noticing it halfway? Stop there and then. A thinner mixture results from less petrol inside your tank, but the next stage remains the same: do not start it.
Coldean: already put petrol in a diesel?
The order of things is short, then. Leave it unstarted, with the ignition off too. Ask the attendants to help you roll it clear of the pump if you are still at the forecourt, whether that is Asda or somewhere else. Ring 0333 366 0103 next, with three answers — the fuel, the rough quantity, and whether it's run.
Corrosion and deposits form the trouble with AdBlue, whereas petrol brings lost protection. So if it was AdBlue, say so — and see its own Coldean page.
One petrol in a diesel task around Coldean costs more than another. Why?
The four situations above are four different jobs, so no single price for this would be fair. What shifts the cost is mostly which of them you're in. After that it is the share — how much petrol was put in against how much the tank takes — and after that where the car is and whether a technician can get to it safely.
That is why our technicians ask three questions before quoting instead of after: what got in, how much, and if it has run. Those replies turn a range into a straight figure.
About Coldean
Coldean is a suburban area located inland in East Sussex, approximately 3.1 miles north of Brighton and Hove. Coldean sits at an elevation of around 74 metres, near the neighbouring areas of Stanmer, North Moulsecoomb, and East Moulsecoomb. Coldean is characterised by its predominantly semi-detached housing stock, typical of many suburban areas in the South East of England. Coldean is also situated within commuting distance of London, at around 44.5 miles away.
Across East Sussex and around Coldean: fuel drain cover
Stanmer, North Moulsecoomb and East Moulsecoomb are among the places around Coldean that the same teams work, answering petrol in diesel call-outs across Coldean's BN postcode area. Our engineers drain wherever the vehicle is — your own drive, a lay-by, a supermarket car park, a forecourt — so it does not have to come to us.
Coldean: still at the pump?
In that case, you couldn't be in a better spot. Keep the vehicle switched off, then ring.