Should You Worry? Petrol in a Diesel Car in Merrivale
Likely less than you already are — provided no one has started it. "Have I wrecked it?" is the first question anyone in Merrivale asks, and the honest answer is generally no, because petrol left in a diesel tank hurts nothing until it is drawn through the fuel system — by ignition priming, by your starter, or by driving. Petrol in Diesel is who to phone, with your engine left off, and so it remains that way. The rest of this page sets out what petrol really does to a diesel, how to judge how far it has got, and how to make sure it doesn't happen to you again.
Your engine and petrol in a diesel: what goes on
On its way through a motor, diesel does two tasks. Lubricating comes before burning; it does both. The high-pressure pump and the injectors are made to extremely fine gaps, and your diesel passing through them is what stops those surfaces from wearing down against each other.
Badly at the first, not at all at the second: that is petrol. The knocking comes from petrol being designed not to ignite when compressed, which is precisely the reverse of what a diesel needs. On top of that it is runnier than diesel, it strips away the protection the fuel system hinges on, and any pump working on that mixture is wearing itself.
Put these together and the shape of the trouble is plain. Not contact but movement is what causes the damage. All a tank with petrol in it amounts to is a fuel fault. 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 your injectors downstream.
Four situations we see around Merrivale: how serious is petrol in a diesel?
Fuelled but not once started — the best it gets. The petrol is in that tank and only the tank, and the job is a drain and a flush where the car sits. This is the one situation that can only really happen at a forecourt, as anywhere else your car has been driven to get there.
A brief spell of running, or just your ignition on. Petrol has come out of your tank and got to your filter and the fuel lines, because your system has been primed. Usually little more than emptying, purging and seeing to the fuel filter, and so still simple.
Driven a few miles. Now the pump has spent these miles running on diluted fuel. The work is that tank, your lines, the filter and clean fuel through the entire circuit, and how hard the vehicle was driven matters as much as how far. Short trips, such as the school run to St Joseph's RC Primary School and Nursery, are one thing. Any miles on the M50, under 3 miles from Merrivale, means your engine working hard throughout, and a run to Hereford, under 15 miles away, is a very different task as well.
Driven till it complained. Knocking, a lumpy idle, smoke, a throttle that has gone soft. What you are hearing is your motor reporting fuel that no longer runs like diesel. Pull up wherever you are — the verge on Blake Avenue, a lay-by, a side street — then leave the car there. What comes first is still the fuel drain and flush-through, and that deals with it, with long-term damage very rare when a vehicle is stopped early.
Merrivale motorists and the 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 is removed by topping up — you are left with a fuller tank, still the same mix. The idea behind that advice — that diesel fuel systems tolerate petrol by percentage — is wrong.
Myth: a current diesel copes with a bit of petrol. If anything, the reverse. Protection counts more on newer diesels, not less, because their fuel passes through smaller parts at higher pressure.
One myth that catches drivers out: if it starts and drives, it must be unharmed. Feed diesel to a petrol motor and it usually will not run, so the driver stops — and the harm stops with them. A diesel fed petrol generally starts, ticks over and drives away as if nothing has happened, whilst your pump grinds. Fine and running are not the same thing.
Myth: "Add some two-stroke oil and drive the car home." It is an old workaround for a distinct issue. None of what petrol diluted gets put back by it — and later, that tank still contains that petrol.
Once the motor has run, part of that petrol is in the fuel filter and your lines, not your tank — and the next start sends it straight back through your pump. So the myth "drain your tank yourself and you are sorted" does not hold. Clearing petrol into a can at the kerbside is also truly hazardous.
How petrol ends up: petrol in a diesel
It's seldom carelessness, and nobody does it on purpose. One way only, because of the nozzles: the slimmer petrol one slips inside a diesel filler with almost no resistance, whereas the diesel one mostly won't fit a petrol motor. That's how the forecourt makes it straightforward.
When routine and the vehicle stop matching, it happens. Any car that is new to you — a hire car, on loan as a courtesy car, or just bought. Two cars on one driveway, one petrol, one diesel. Your ordinary forecourt, its pumps suddenly in a different order. Rushing for a train at Ledbury and filling up en route. Exactly the moment it occurs: after years of driving petrol, a driver fills a diesel Volkswagen Golf for the first time. Add a back seat full of children, a phone call or rain, and the hand takes over.
Merrivale people: how to avoid petrol in a diesel next time
- Not every forecourt in the UK keeps to green for unleaded and black for diesel, even if most generally do. Read the pump's label; the colour is only a clue.
- Check the filler flap. Many cars state the fuel inside the flap or on the cap. Look at it on the first fill in a car you don't know.
- A coloured fob or a sticker on your diesel's key does more than any amount of meaning to remember, in a house with one of each.
- "Diesel", aloud, before you pick up the nozzle — each time a new or hired car needs its first tank. It sounds silly. 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.
- Up to a point, a misfuel inhibitor helps: some diesels come with a filler designed to block a petrol nozzle, and aftermarket devices exist for the remainder. Count it as a backstop, then keep reading the petrol pump.
- Stop as soon as you realise. Less petrol inside your tank makes a thinner blend. It does not change what to do next, which is still not to start it.
Merrivale: already put petrol in a diesel?
In that case, there's only a short order of things. Leave it unstarted, with your ignition switched off too. The staff at the forecourt — whether at Morrisons itself or wherever you filled up — will usually help push it clear of the pump if you ask. What went in, roughly how much, and if it's run: tell us those when you phone 0333 366 0103.
Say so if it was AdBlue rather than petrol: it's a separate fault, with its own page for Merrivale, because AdBlue brings corrosion and deposits instead of lost lubrication.
One petrol in a diesel job in Merrivale costs more than another. Why?
There's no honest single quote for this, since the four scenarios above are four different jobs. What moves the cost is mostly which of them you are in. Next it is the ratio — how much petrol got in against how much that tank takes — and after that where your car is and whether our van can reach it safely.
What got in, how much, and whether it has run — three queries our technicians ask before quoting, not after, for precisely that reason. A range turns into a straight figure when the answers are in.
About Merrivale and its setting
Merrivale is a suburban area in Herefordshire, situated inland at an elevation of 46 metres, and is located approximately 11.7 miles from Hereford. Merrivale has a population of around 2794 people and is characterised by predominantly detached housing. Merrivale is part of the wider West Midlands region, and is about 108.6 miles from London. Merrivale is near other places such as Ashfield, Ross-on-Wye, and Archenfield.
Across Herefordshire and around Merrivale: fuel drain cover
Ashfield, Ross-on-Wye and Archenfield are among the places near Merrivale that the same vans work, answering petrol in diesel jobs across Merrivale's HR postcode area. No need to bring your car to us. Forecourts, supermarket car parks, lay-bys and your own drive are all places where we work.
Merrivale: still at the petrol pump?
Then, you could not be in a better position. Keep it off. Ring.