Sharpness: Petrol in a Diesel Car? How Worried to Be
Likely less than you already are — provided nobody has started the vehicle. Until the ignition primes your pump, your starter cranks, or your car is driven, petrol in a diesel tank just waits there and does nothing. Which means the truthful reply to the first Sharpness question — "have I wrecked it?" — normally no. Leave the engine off and phone Petrol in Diesel — that is how you keep it like that. Further down, this page sets out what petrol actually does inside a diesel, how far it may have got, and how to stop it happening to you a second time.
The motor and petrol in a diesel: what goes on
On its way through an engine, diesel does two jobs. It ignites, and before it combusts it protects. The high-pressure pump and the injectors are designed to very fine clearances, and your diesel passing through them is what keeps those surfaces from wearing down against each other.
Badly at the first, not at all at the second: that is petrol. A pump running on a petrol mixture is wearing itself out, since petrol is runnier 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 needs from its fuel — and that is where the knocking comes.
Put these together and the shape of the trouble is clear. The damage is done by movement, not by contact. All a tank with petrol in it amounts to is a fuel issue. A pump that has been running on that petrol is the start of a mechanical one, and whatever a worn pump sheds moves on with the fuel to the injectors further on.
Petrol in a diesel around Sharpness: how serious is it? Four cases
The best case there can be: filled up, not once started. That petrol is inside the tank and just your tank, and the task is a drain and a flush where your car stands. This is the one situation that can only really happen on a forecourt, since anywhere else your car has been driven to get there.
Ignition on, or started for a moment. With the system primed, the lines and filter already hold petrol that has come from that tank. Drain, flush, see to the fuel filter: still usually easy.
Those few miles driven meant your pump running on fuel weakened by petrol the whole way. Distance is only half of it; how hard it was driven counts just as much. Either way this work runs to your tank, the lines, the filter and fresh fuel through the entire system. On the school run to Sharpness Primary School, the mileage is small. Getting as far as Gloucester, under 15 miles away, makes a very different job — as does any distance on the M5, under 5 miles from Sharpness, with the engine working hard all the way.
Driven until it complained. Rattling, a ragged idle, smoke, a throttle that has gone soft. The fuel isn't acting like diesel any more, and your motor is saying so. Whether it's the verge on New Street, a lay-by or a side road, stop where you are then leave it. The fuel drain and flush-through still come first, and they deal with it: when a car is pulled over early, permanent damage is very unusual.
What Sharpness people get told about petrol in a diesel — and the myths in it
It will not be fine. The myth: "Fill it the rest of the way with diesel and it will be." Nothing comes out when you top up — your tank simply carries more of the same mixture. Percentage isn't how a diesel fuel system tolerates petrol, whatever that guidance assumes.
Not so: a modern diesel copes with a bit of petrol. If anything, the reverse. A newer diesel runs its fuel through finer components at higher pressure, which makes the protection count more, not less.
Myth: "If it starts and drives, there's no damage done." This is the one that catches people. Diesel in a petrol motor usually leaves a motor that will not run: the motorist stops, and so does the harm. A diesel fed petrol generally starts, idles and drives away as though nothing has happened, whilst your pump grinds. Running is not the same as fine.
Myth: "Add some two-stroke oil and drive it home." It's an outdated workaround for a distinct fault. The petrol is still in the tank afterwards, and what it has diluted is not put back.
Myth: "Drain that tank yourself and you are sorted." After your engine has run, some of the petrol is no longer inside your tank: it is in the filter and your lines, and it goes straight back through the pump on your next start. Besides, petrol emptied into a can by the road is truly dangerous.
Why petrol in a diesel occurs so easily
It is seldom carelessness, and nobody does it on purpose. The petrol nozzle is the smaller of the two and slides into a diesel filler with almost no resistance; a diesel nozzle mostly won't go into a petrol motor at all. The forecourt makes it simple, and the mistake runs one way.
Habit and the vehicle getting out of step is how it occurs. Hire cars, courtesy cars, and vehicles that are new to you. A household with one petrol and one diesel on the driveway. Your normal forecourt, its pumps now in a different order. A hurried fill en route to Lydney with a train to catch. Years of petrol motors behind you, a diesel Skoda Octavia in front of you at the forecourt for its first tank — that is when. 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 around Sharpness: avoiding petrol in a diesel
- Not every forecourt in the UK keeps to green for unleaded and black for diesel, even if most usually do. Read the petrol pump's label; the colour is just a clue.
- The first fill in a strange car is the time to check the filler flap — on it, or on the cap, plenty of cars state the fuel they take.
- Good intentions count for less than a sticker or a fob in a vivid colour on the diesel's key if a home has one of each. So label it.
- Before the nozzle comes off the pump the first time you fill a hired or new car, say "diesel" out loud. Silly, perhaps, yet it does the trick.
- Thinking about something else is when this becomes an easy mistake to make, and so tuck your phone away then keep your mind on the petrol pump.
- Some diesels come with a filler built to refuse a petrol nozzle, and devices you can add exist for cars without one. Such an inhibitor helps up to a point — as a backstop, not a reason to stop reading the petrol pump.
- Less petrol makes a thinner mixture, so stop as soon as you realise — though remembering that your next step is unchanged. It's still not to fire it up.
Sharpness: already put petrol in a diesel?
The order of things is brief, then. Starting it is out, and so is switching on the ignition. If you are still on the forecourt — Co-op or anywhere else — ask the staff to help you roll the car away from the pump. What went in, roughly how much, and if it's run: tell us that when you phone 0333 366 0103.
AdBlue, not petrol? Then tell us. Corrosion and deposits, not lost lubrication, make it a different problem — Sharpness has a page just for it.
What makes one Sharpness petrol in a diesel task cost more than the next
The four situations above are four different jobs, so no single quote for this would be fair. Which of them you're in is mostly what moves the cost. Two things come after that: the petrol that got in as a proportion of what the tank takes, then the spot the vehicle is in and whether a van can get to it safely.
What went in, how much, and whether it has run — three queries we ask before costing, not after, for exactly that reason. Given the replies, you get a straight figure instead of a range.
About Sharpness
Sharpness is a small coastal village in Gloucestershire, situated near the Severn Estuary at an elevation of around 21 metres. Sharpness lies within a short distance of several nearby settlements, including Newtown, Wanswell, and Brookend. Sharpness has a mix of housing types, but terraced houses are particularly prevalent in the village. Sharpness is located approximately 14 miles from Gloucester and around 102 miles from London.
Fuel drain cover in Sharpness and across Gloucestershire
Petrol in diesel jobs around Sharpness — part of the GL postcode area — go to vans that also cover the locations around it, Newtown, Wanswell and Brookend among them. The vehicle does not need to move to us: we drain on a forecourt, in a supermarket car park, in a lay-by or on your own drive.
Sharpness: still at the petrol pump?
Then you're in the best spot there is. Keep it off. Ring.