Should You Worry? Petrol in a Diesel Car in Cold Ash
Far less than you likely are, if it has not been started. Everyone around Cold Ash begins with "have I ruined it?", and the fair answer is generally no: petrol resting inside that tank of any diesel stays harmless until priming, cranking or driving draws it into your fuel system. Petrol in Diesel is who to call, with the motor left off, so it remains that way. Below, you will find what petrol actually does inside a diesel, how far it might have gone, and how to stop it happening to you again.
Petrol in a diesel: what does it do to the engine?
On its way through an engine, diesel has two tasks. Before it burns, it protects — then it combusts. What stops the surfaces inside your high-pressure pump and your injectors from wearing down against one another is your diesel flowing through them — they're made to extremely fine clearances.
The second task petrol does not do at all, and the first it does badly. The rattling comes from petrol being designed not to ignite when compressed, which is exactly the reverse of what a diesel needs. On top of that it is runnier than diesel, it strips away the lubrication the system rests on, and any pump working on such a blend is wearing itself.
The shape of the trouble is clear when you put those together. It is movement that does the harm, not contact. Where the petrol is only in the tank, it is a fault of fuel, nothing more. The beginning of a mechanical problem is a pump that has been working on that petrol — and whatever a worn pump sheds travels on with the fuel to your injectors beyond it.
Cold Ash, petrol in a diesel: four cases, from mild to significant
The best case there is: filled up, not once started. Just that tank has petrol in it, so the job is draining that tank and flushing your system where the car stands. This scenario can only truly occur at a forecourt: anywhere else, your car got there by being driven.
Started for a second, or just your ignition on. Petrol has come out of your tank and reached your filter and your lines, because your system has been bled. Drain, flush, deal with the filter: still usually straightforward.
A few miles driven, and your pump has spent every one of them working on weakened fuel. Tank, lines, filter, then clean fuel run through the whole circuit: that's this work, and the way your car was driven matters as much as the miles. On the school run to St Finian's Catholic Primary School, the miles is small. A run as far as Oxford, under 25 miles away, is a very different job. So is any mileage on the M4, under 3 miles from Cold Ash, where your engine has been working hard throughout.
Clattering, an uneven idle, smoke, a throttle gone soft: driven till it complained. The engine is telling you the fuel is no longer behaving like diesel. Stop on the spot — on the verge on Strouds Meadow, at the kerb, down a side road — and don't move it. Lasting damage is very unusual when a vehicle is stopped soon, and the drain and flush-through that still go first sort it out.
Petrol in a diesel myths Cold Ash drivers hear
Myth: "Fill it the rest of the way with diesel and it'll be fine." It will not. A fuller tank of the same mixture is all it gives, since topping up takes out nothing. That advice supposes a diesel fuel system tolerates petrol by percentage. It does not.
Myth: a modern diesel copes with a bit of petrol. Rather, the opposite. At higher pressure, through smaller components: that's how a current diesel moves its fuel, so the protection matters more, not less.
"It starts, it drives, so no harm done" — the myth that trips up more people than any other. Diesel in a petrol motor generally means a motor that won't run: the driver stops, and so does the damage. A diesel fed petrol normally starts, ticks over and drives away as if nothing has happened, whilst your pump wears. Running doesn't mean fine.
Myth: "Add some two-stroke oil and drive the car home." It's an old fix for a different fault. What petrol has diluted remains thinned, and that petrol stays in the tank regardless.
Once the engine has been run, part of that petrol sits in the filter and the lines, not your tank — and your next start sends it straight back through the pump. So the myth "drain the tank yourself and you're sorted" doesn't hold. Draining petrol into a can at the roadside is also genuinely dangerous.
How it happens: petrol in a diesel
It is rarely carelessness, and no one does it on purpose. One way only, because of the nozzles: the narrower petrol one slips inside a diesel filler with almost no resistance, while the diesel one mostly won't fit a petrol car. That's how the forecourt makes it straightforward.
Habit and the vehicle getting out of step is how it takes place. Courtesy car, hire car, or a vehicle that's brand new. 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 hurried fill en route to Thatcham. Exactly the moment it takes place: after years of driving petrol, a driver fills a diesel Renault Megane for the first time. Add rain, a phone call or a back seat full of kids, and the hand does what it has always done.
Next time you fill up in Cold Ash: preventing petrol in a diesel
- Not every forecourt in the UK follows green for unleaded and black for diesel, though most generally do. Check the pump's label; the colour is just a hint.
- Many motors state the fuel inside your filler flap or on the cap, so check there on your first fill in any motor you don't know.
- A coloured fob or a sticker on your diesel's key does more than any amount of meaning to remember, for a household with one of each.
- It seems daft and it works: on the first fill in a new or hired car, say "diesel" out loud before you take the nozzle off the petrol pump.
- Mistakes like this are straightforward to make while your mind is on something else, so your phone goes away.
- Add-on devices exist for cars without one, and some diesels are built 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 the moment you realise. Less petrol inside that tank makes a weaker blend. It doesn't change what to do next, which is still not to start the vehicle.
Petrol already in a diesel in Cold Ash? Start here
Then the order of things is short. Leave it unstarted, with the ignition off as well. Ask the attendants to help you push it away from the petrol pump if you are still at the forecourt, whether that is Esso or somewhere else. Call 0333 366 0103 next, with three answers — your fuel, the rough amount, and if it has run.
Corrosion and deposits are the trouble with AdBlue, whereas petrol brings lost protection. So if it was AdBlue, say so — and read its own Cold Ash page.
Cold Ash petrol in a diesel tasks: why one costs more than another
A fair single price doesn't exist here: four scenarios, four separate tasks. What moves your cost is mostly which of them you are in. Where the car is counts too, and whether a van can safely reach it, after the proportion of petrol to what the tank holds.
What went in, how much, and whether it has run — three questions we ask before costing, not after, for exactly that reason. Those answers are what change a range into one firm number.
About Cold Ash, for a moment
Cold Ash is a rural village in Berkshire, situated inland at an elevation of 122 metres, with a mix of detached housing and open countryside. Cold Ash lies near the villages of Ashmore Green and Bucklebury Alley, and is surrounded by woodland areas like Stone Copse. Cold Ash is located approximately 22.8 miles from Oxford and 49.3 miles from London, making it a relatively secluded community. Cold Ash has a population of around 1063 residents, living in predominantly detached homes.
Across Berkshire and in Cold Ash: fuel drain cover
The vans answering petrol in diesel jobs in Cold Ash, in the RG postcode area, also work the places near it, Ashmore Green, Bucklebury Alley and Stone Copse included. The car does not need to come to us: our engineers drain at a forecourt, in a supermarket car park, in a lay-by or on your own drive.
At the pump in Cold Ash, still?
Then you're in the best place there is. Leave the car switched off, and ring.