Should You Worry? Petrol in a Diesel Car in Frenze
Less than you probably are, if it hasn't been started. Until your ignition primes your pump, your starter cranks, or your vehicle is driven, petrol in a diesel tank simply waits there and does no harm. Which makes the honest reply to the first Frenze query — "have I ruined it?" — normally no. Petrol in Diesel is who to call, with the motor kept off, and so it remains that way. The remainder of this page covers what petrol actually does to a diesel, how to tell how far it has got, and how to make sure it doesn't happen to you again.
What petrol in a diesel does to the engine
Diesel has two jobs on its way through an engine. It lubricates to begin with, and only then does it burn. The high-pressure fuel pump and the fuel injectors are made to extremely fine tolerances, and your diesel passing through them is what stops those surfaces from grinding against each other.
Of these two jobs, petrol manages the first badly and the second never. 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 thinner than diesel, it strips away the protection your system hinges on, and any pump working on that blend is wearing itself.
Put these together and the shape of the trouble is clear. Not contact but circulation is what does the harm. All a tank with petrol in it amounts to is a fuel fault. After the pump has been running on that petrol, a mechanical fault has started: whatever is shed by a pump that is wearing is carried downstream to the injectors with the fuel.
Frenze, petrol in a diesel: four cases, from mild to serious
Fuelled but never started — as good as it gets. That petrol is in that tank and just the tank, and the task is a drain and a flush where your car sits. This is the one situation that can only really occur at a forecourt, because anywhere else your car has been driven to get there.
A moment's running, or just your ignition on. The fuel system has been primed, so petrol has left the tank and reached your filter and your lines. That is usually still a straightforward task — a drain, a flush, and the filter seen to.
Your pump now worked a couple of miles on thinned fuel — that's what driving the car meant. The work is the tank, the lines, your filter and clean fuel through the entire circuit, and how hard the vehicle was driven matters as much as how far. On the school run to Diss Infant Academy and Nursery, the miles is small. Very different once more: a run to Norwich, under 25 miles away, or some mileage on the M11, under 50 miles from Frenze, where your engine never stopped running hard.
It complained, and only then stopped: smoke, knocking, a throttle gone soft, an idle gone uneven. The engine is telling you the fuel is no longer behaving like diesel. Stop wherever you are — the verge on Sandy Lane, a lay-by, a side street — and leave it where it is. A vehicle stopped early very rarely has long-term damage, as the drain and the flush-through, which still come first, deal with it.
Frenze drivers and that petrol in a diesel stories they hear
Myth: topping up to full with diesel makes it fine. It does not. Nothing is removed by topping up — you're left with a bigger tank, still the same mixture. A diesel fuel system does not tolerate petrol by percentage in the way that guidance presumes.
Myth: "A modern diesel can cope with a bit of petrol." If anything, the reverse. At higher pressure, through finer parts: that's how a modern diesel moves its fuel, so the lubrication matters more, not less.
This is the one that catches drivers. Myth: "If it starts and drives, there is no damage done." Diesel in a petrol motor generally leaves a motor that won't run: the motorist stops, and so does the harm. Feed petrol to a diesel and it normally fires up, ticks over and pulls away as if nothing happened — all the while its pump wears. Fine and running are not the same at all.
An outdated workaround for a distinct fault is behind this one. Myth: "Add some two-stroke oil and drive the car home." None of what petrol thinned gets put back by it — and later, your tank still holds that petrol.
Myth: "Drain the tank yourself and you're sorted." After your engine has run, some of that petrol is no longer inside that tank: it's in the filter and the lines, and it goes straight back through your pump at the next start. Also, a can of petrol drained at the roadside is truly dangerous.
Why petrol in a diesel occurs at all
No one does it on purpose, and it is seldom carelessness. One way only, since of the nozzles: the slimmer petrol one slips inside a diesel filler with almost no resistance, whereas the diesel one generally will not fit a petrol car. That's how the forecourt makes it simple.
When habit and the vehicle stop matching, it happens. Hire cars, courtesy cars, and cars that are new to you. 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 outside Diss and filling up en route. A new-to-you diesel Volkswagen Golf, its first fuelling, and a driver accustomed to petrol: exactly when it takes place. Throw in rain, a phone call or a back seat full of children, and the hand does what it has always done.
Next time you fill up in Frenze: preventing petrol in a diesel
- 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 counts.
- The first fill in a new motor is the time to check your filler flap — on it, or on the cap, many motors state which fuel they take.
- Mark your key. In a house with one of each, a coloured fob or a sticker on your diesel's key does more than any amount of meaning to remember.
- Before the nozzle comes off the pump the first time you fuel a hired or new motor, say "diesel" out loud. Daft, yes, yet it works.
- Whilst you are thinking about something else, this is an easy mistake to make — so put the phone away.
- Add-on devices are available for motors without one, and some diesels come with a filler that will not accept a petrol nozzle. Useful — but a safety net only, never a reason to stop checking the label.
- Stop as soon as you notice. Less petrol inside that tank means a thinner blend. It doesn't change what to do next, which is still not to start the car.
Already put petrol in a diesel in Frenze?
Then the order of things is brief. Do not fire it up, and do not turn your ignition on. The attendants on the forecourt — whether at Shell itself or wherever you filled up — will normally help roll it away from the petrol pump if you ask. Next, 0333 366 0103. We'll ask what went in, roughly how much, and if it's been run.
If it was AdBlue and not petrol, say so. That is a different problem — corrosion and deposits rather than lost protection — and it has its own page for Frenze.
Why one petrol in a diesel task around Frenze costs more than another
A fair single price does not exist here: four scenarios, four separate tasks. The scenario itself does most of the work of moving your cost. Next it is the proportion — how much petrol was put in against how much the tank takes — and then where the vehicle is and whether a van can reach it safely.
What was put in, how much, and if it has run — three queries our engineers ask before pricing, not after, for precisely that reason. Those answers turn a range into a straight figure.
About Frenze, for a moment
Frenze is a small hamlet in Norfolk, situated inland at an elevation of around 30 metres, and is located near the villages of Walcot Green and Scole Common. Frenze lies approximately 18 miles south of Norwich and about 81 miles northeast of London, in a rural area characterized by detached housing. Frenze has a population of around 559 people and is part of the wider landscape of the Eastern region. Frenze is also close to the town of Diss, which provides local amenities and services.
Fuel drain cover across Norfolk, Frenze included
Our teams answering petrol in diesel calls around Frenze, in the IP postcode area, equally work the locations around it, Walcot Green, Scole Common and Diss among them. A forecourt, a supermarket car park, a lay-by or your own drive are all spots we work, and the vehicle doesn't need to come to us.
At the pump in Frenze, still?
Nothing beats it: that is where you now are. Keep it off. Phone.