Should You Worry? Petrol in a Diesel Car in Cadnam
Likely less than you are now — as long as no one has started it. Everyone around Cadnam begins with "have I ruined it?", and the fair answer is usually no: petrol left in the tank of a diesel remains harmless till priming, cranking or driving pulls it into your fuel system. To leave the car like that, call Petrol in Diesel then leave the engine alone. Read on for three things: the effect petrol has inside a diesel motor, the signs of how far it has spread, and ways to make sure you don't do it again.
What petrol in a diesel does to the engine
Diesel does two jobs on its way through an engine. Lubricating comes before burning; it does both. The high-pressure pump and the injectors are built to extremely fine tolerances, and your diesel passing through them is what stops those surfaces from wearing against each other.
Petrol handles the first job badly and the second not at all. Being less viscous than diesel, petrol strips out the protection a fuel system needs, leaving a pump on the blend wearing itself. It's equally made to resist igniting under compression — the reverse of what a diesel needs — which is why you get the knocking.
The shape of the trouble is plain when you put those together. Contact does not do the damage — circulation does. Petrol in a tank is a fuel problem. Once the pump has been running on that petrol, a mechanical fault has begun: anything shed by a pump that is wearing down is carried onward to the injectors with the fuel.
How bad is petrol in a diesel? Four situations our engineers see in Cadnam
Filled up, not once started. The best case there is. Being at a forecourt is what makes this possible: elsewhere, your car has been driven there to begin with. With the petrol kept inside that tank alone, it's cleared and rinsed on the spot, and nothing more is needed.
The ignition turned on, or a short start. Your system has been primed, so petrol has left your tank and got to the fuel filter and the fuel lines. That's usually still a simple job — a drain, a flush, and your filter seen to.
Driven a few miles. Now the pump has spent those miles running on weakened fuel. Tank, lines, filter, then fresh fuel run through the entire system: that is the work, and the way the car was driven counts as much as the mileage. Driving the children to Bartley Church of England Junior School is one sort of trip. Any mileage on the M27, under a mile from Cadnam, means the engine has worked hard throughout, and a run to Southampton, under 10 miles away, is a very different task as well.
Driven on until it protested — knocking, smoke, a ragged idle, a dead throttle. That's the engine telling you its fuel has stopped behaving like diesel. Stop wherever you are — the verge on Southampton Road, a lay-by, a side street — then leave the vehicle where it is. What comes first is still the fuel drain and flush-through, and that takes care of it, with long-term damage very unusual when a car is pulled over soon.
What Cadnam 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 bigger tank of the same mix. The idea behind that advice — that diesel fuel systems accept petrol by percentage — is wrong.
"Newer diesels can handle a little petrol" — a myth, and closer to the opposite. At higher pressure, through more precise parts: that's how a newer diesel handles its fuel, and so the lubrication counts more, not less.
"It starts, it drives, and so no harm done" — the myth that catches most people than any other. The driver of a petrol motor fed diesel normally stops, because it will not run, and the damage stops there. Feed petrol to a diesel and it usually fires up, idles and drives away like nothing happened — all while its pump is wearing. Running is not the same as fine.
Myth: "Add some two-stroke oil and drive it home." It is an old fix for a distinct issue. None of what petrol weakened gets put back by it — and afterwards, the tank still contains that petrol.
Myth: "Drain that tank yourself and you're sorted." Once your engine has been run, some of that petrol is no longer inside the tank: it is in the fuel filter and the lines, and it goes straight back through your pump on your next start. Draining petrol into a can by the roadside is also genuinely risky.
Petrol in a diesel: how does it happen?
On purpose? Never. Through carelessness? Seldom, if ever. A diesel nozzle generally will not fit a petrol vehicle, but the slimmer petrol nozzle goes into the filler of a diesel almost without resistance — so forecourts make this one mistake easy, and just in one direction.
When habit and your car stop matching, it occurs. A new motor, a hire car or a courtesy car. Two vehicles on one driveway, one petrol, one diesel. A familiar forecourt with the pumps in a different order. A train to catch, and a rushed fill on the way to Ashurst New Forest. A new-to-you diesel Volkswagen Golf, its first fuelling, and a driver accustomed to petrol: precisely when it takes place. The hand does what it has always done when you add rain, a phone call or a back seat full of kids.
Preventing petrol in a diesel next time you fill up in Cadnam
- Check the petrol pump, not the colour. In the UK unleaded handles are usually green and diesel black, yet not on every forecourt. The label is what matters.
- In a vehicle you do not know, look inside the flap over your filler or at the cap before the first fill: many vehicles print the fuel there.
- One of each in the house? Mark the key to the diesel — a coloured fob, a sticker — because meaning to remember isn't enough.
- "Diesel", out loud, before you lift the nozzle — every time a new or hired car gets its first tank. It seems daft. It works.
- While you're thinking about something else, this is an easy mistake to make — so tuck the phone away.
- Add-on devices exist for cars without one, and some diesels come with a filler that won't take a petrol nozzle. Useful — but a backstop only, never a reason to stop checking the label.
- Less petrol makes a thinner blend, and so stop the moment you notice — while remembering that your next step is unchanged. It's still not to crank it.
Cadnam: already put petrol in a diesel?
In that case, there's just a short order of things. Do not start it, and do not switch the ignition on. Yet at the forecourt, at Texaco or anywhere else? Ask the staff to help you roll the vehicle away from the petrol pump. Then ring 0333 366 0103 and tell us what went in, about how much, and whether it's run.
If it was AdBlue and not petrol, say so. That's a different fault — corrosion and deposits instead of lost protection — and it has its own page for Cadnam.
One petrol in a diesel job around Cadnam costs more than another. Why?
The four situations above are four different jobs, so no single price for this would be honest. Which of them you are in is mostly what moves the cost. Two things come after that: the petrol that went in as a proportion of what your tank takes, then the spot the car is in and whether our van can get to it safely.
What was put in, how much, and if it's run — three questions our technicians ask before quoting, not after, for precisely that reason. With the answers, you get a straight figure instead of a range.
About Cadnam
Cadnam is a small village in Hampshire, situated on the banks of the River Blackwater at an elevation of 31 metres. Cadnam lies near the larger city of Southampton, approximately 7.7 miles away, and is surrounded by smaller settlements such as Bartley and Wittensford. Cadnam has a population of around 667 people and is characterised by predominantly detached housing. Cadnam is located in the South East region of England, about 74.8 miles from London.
Cadnam and Hampshire: where our fuel drain cover runs
Petrol in diesel call-outs in Cadnam — part of the SO postcode area — go to vans that likewise cover the places round it, Bartley, Wittensford and Newbridge included. Our engineers drain wherever the vehicle is — your own driveway, a lay-by, a supermarket car park, a forecourt — so it never needs to come to us.
Cadnam: still at the petrol pump?
No position is better: that's where you are. Keep the vehicle switched off, then ring.