Should You Worry? Petrol in a Diesel Car in Cwm Fields
Probably less than you are now — provided nobody has started it. Until your ignition primes the pump, your starter turns, or your car is driven, petrol in a diesel tank just rests there and does nothing. Which makes the truthful reply to the first Cwm Fields query — "have I ruined it?" — normally no. Keep it that way: leave the engine off then call Petrol in Diesel. The remainder of this page sets out what petrol actually does to a diesel, how to judge how far it has got, and how to make sure it does not happen to you a second time.
Petrol in a diesel: what does it do to the motor?
Passing through an engine, diesel does two things at once. Lubricating comes before burning; it does both. What stops the surfaces inside the high-pressure pump and the fuel injectors from wearing against one another is your diesel passing through them — they are made to extremely fine tolerances.
Of these two jobs, petrol manages the first poorly and the second never. A pump running on a petrol mix is wearing itself out, since petrol is thinner than diesel and strips out the lubrication the fuel system depends on. Petrol is also designed to resist igniting under compression — the opposite of what a diesel wants from its fuel — and that is where any knocking comes.
Put these together and the shape of the problem is clear. Not contact but movement is what causes the harm. Where the petrol is only in the tank, it is an issue of fuel, nothing more. After the pump has been running on that petrol, a mechanical fault has begun: whatever is shed by a pump that is wearing down travels downstream to your injectors with your fuel.
Petrol in a diesel around Cwm Fields: how bad is it? Four situations
Filled but not once started — as good as it gets. That petrol is inside your tank and just your tank, and the job is a drain and a flush where your car sits. This is the one situation that can only really occur on a forecourt, because anywhere else the car has been driven to get there.
A moment's running, or merely your ignition on. Petrol has left your tank and got to your filter and your lines, because the fuel system has been bled. That's generally still a simple job — a drain, a flush, and the fuel filter dealt with.
Your pump now worked a couple of miles on weakened fuel — that's what driving the car does. Tank, lines, filter, then fresh fuel put through the whole circuit: that is this work, and the way the car was driven counts as much as the mileage. Short trips, such as the school run to the local primary school, are one thing. Driving as far as Newport, under 10 miles away, makes a very different task — as does any miles on the M4, under 10 miles from Cwm Fields, with the engine working hard all the way.
Driven on till it protested — rattling, smoke, a ragged idle, a dead throttle. That's the engine telling you its fuel has stopped acting like diesel. Stop wherever you are — the verge on Blaendare Road, a lay-by, a side street — then leave the car there. The fuel drain and flush still come first, and they take care of it: if a vehicle is stopped soon, lasting damage is very uncommon.
What Cwm Fields drivers get told about petrol in a diesel — and the myths in it
False: topping up to full with diesel makes it fine. It does not. Nothing is removed by topping up — you are left with a fuller tank, still the same mixture. The assumption behind that guidance — that diesel fuel systems accept petrol by percentage — is wrong.
If anything, the reverse is true. Myth: "A current diesel can cope with a bit of petrol." A modern diesel sends its fuel through finer parts 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 motorists than any other. Diesel in a petrol motor normally means a motor that will not run: the driver stops, and so does the harm. Nothing seems to have happened when a diesel fed petrol fires up, ticks over and drives away, which it usually will; meanwhile the pump wears. Running is not the same as fine.
"A drop of two-stroke oil and drive it home" — a myth, borrowed from a fix from years ago, for a different fault. That petrol is still inside your tank after that, and whatever it has weakened isn't put back.
"Drain it yourself and you are sorted" — a myth, since after it's been running some petrol lies in the fuel filter and lines, ready to go straight back through the pump on the next start. It is also really hazardous to drain petrol into a can by the roadside.
How does petrol in a diesel take place?
Carelessness is seldom the cause, and nobody means to do it. One way only, since of the nozzles: the smaller petrol one slips inside a diesel filler with almost no resistance, while the diesel one generally won't fit a petrol car. That is how the forecourt makes it straightforward.
When routine and the vehicle stop matching, it occurs. A new car, a hire car or a courtesy car. A household with one petrol and one diesel on the driveway. A well-known forecourt with the pumps in a different order. A train to catch, and a rushed fill en route to Pontypool and New Inn. A new-to-you diesel Volkswagen Passat, its first fuelling, and a motorist used to petrol: exactly when it happens. The hand repeats what it has always done once you add rain, a phone call or a back seat full of kids.
Preventing petrol in a diesel next time you fill up in Cwm Fields
- Read the petrol pump, not the colour. In the UK unleaded handles are normally green and diesel black, yet not on every forecourt. The label is what matters.
- The first fill in an unfamiliar motor is the time to check the filler flap — on it, or on the cap, plenty of cars state which fuel to use.
- Good intentions do less than a sticker or a fob in a bright colour on your diesel's key when a household has one of each. So label it.
- It sounds daft and it works: on your first fill in a new or hired car, say "diesel" aloud before you take the nozzle off the petrol pump.
- Put your phone away. This is an easy mistake to make while you're thinking about something else.
- Add-on devices are available for vehicles without one, and some diesels come with a filler that will not accept a petrol nozzle. Helpful — but a safety net only, never a reason to stop checking the label.
- Less petrol means a weaker mix, and so stop the moment you notice — while remembering that the next stage is unchanged. It is still not to crank it.
Already put petrol in a diesel in Cwm Fields?
In that case, there is just a short order of things. Starting it is out, and so is switching on your ignition. If you are still on the forecourt — Tesco or anywhere else — ask the attendants to help you roll the vehicle away from the pump. Call 0333 366 0103 next, with three facts — your fuel, the rough quantity, and whether it has run.
Say so if it was AdBlue rather than petrol: it is a different fault, with its own page for Cwm Fields, because AdBlue brings corrosion and deposits instead of lost protection.
One petrol in a diesel job around Cwm Fields costs more than another. Why?
A fair single price doesn't exist here: four scenarios, four separate tasks. The scenario itself does most of the work of moving the cost. The share counts next, meaning how much of the tank is petrol, followed by the location of your car and whether reaching it is safe for our van.
Ahead of any quote, not after, we ask three questions: your fuel that went in, the volume, and if it has run. That is why. With the answers, there is a straight figure rather than a range.
About Cwm Fields itself
Cwm Fields is a suburban area in Torfaen, situated on the riverside with a mix of terraced housing. Cwm Fields has a population of around 2422 people and is located near the communities of Trosnant, Cwmynyscoy, and Pontymoel. Cwm Fields sits at an elevation of 168 metres, overlooking the surrounding landscape. Cwm Fields is close to Newport, the nearest city, which is approximately 7.7 miles away.
Cwm Fields and Torfaen: where our fuel drain cover reaches
Cwm Fields waits in the NP postcode area, and our vans that answer petrol in diesel jobs there work the places around it as well — Trosnant, Cwmynyscoy and Pontymoel among them. The vehicle doesn't need to come to us: our engineers drain on a forecourt, in a supermarket car park, in a lay-by or on your own driveway.
In Cwm Fields and still at the petrol pump?
No position is better: that's where you now are. Call, and leave it turned off.