How Worried Should You Be? Petrol in a Diesel Car in Milton Ernest
Probably less than you are now — as long as no one has started the car. Until the ignition primes the pump, your starter turns, or your vehicle is driven, petrol in a diesel tank just rests there and does nothing. Which means the truthful reply to that first Milton Ernest query — "have I ruined it?" — usually no. Keep it that way: leave your engine off and phone Petrol in Diesel. 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 an engine, diesel has two tasks. It combusts, and before it combusts it lubricates. Extremely fine tolerances go into the injectors and your high-pressure pump, and just your diesel running through stops their surfaces grinding together.
Poorly at the first, not at all at the second: that's petrol. A pump working on a petrol mixture is wearing itself out, since petrol is runnier than diesel and strips out 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 clattering comes.
The shape of the trouble is clear once you put those together. Contact does not do the damage — movement does. Petrol in a tank is a fuel issue. The beginning of a mechanical problem is a pump that has been running on that petrol — and whatever a worn pump sheds travels on with your fuel to the injectors downstream.
Milton Ernest, petrol in a diesel: four cases, from mild to major
Fuelled, and not started: no case is better. At a forecourt, and genuinely only there, the petrol is still confined to your tank — since anywhere else your car was driven to reach it. The job is emptying and purging on the spot.
A moment's running, or just the ignition on. With the system primed, the lines and filter now hold petrol that has come from the tank. Drain, flush, see to your filter: still usually simple.
The pump now worked a few miles on weakened fuel — that is what driving it does. The work is the tank, your lines, the filter and fresh fuel through the entire system, and how hard the car was driven matters as much as how far. On the school run to Milton Ernest CofE Primary School, the miles is short. A run as far as Milton Keynes, under 15 miles away, is a very different task. So is any distance on the M1, under 15 miles from Milton Ernest, where the engine has been working hard throughout.
Driven on till it complained — knocking, smoke, a lumpy idle, a dead throttle. The motor is telling you the fuel is no longer behaving like diesel. Leave it wherever it stops: a lay-by, a quiet street, the verge on Rushden Road. The drain and flush-through still go first, and they sort it out: when a car is stopped early, lasting damage is very uncommon.
Petrol in a diesel stories Milton Ernest drivers hear
False: topping up to full with diesel makes it fine. It does not. Nothing is removed when you top up — that tank simply holds more of the same blend. The assumption behind that advice — that diesel fuel systems tolerate petrol by percentage — is wrong.
"Modern diesels can handle a little petrol" — a myth, and closer to the reverse. At higher pressure, through smaller parts: that's how a current diesel handles its fuel, and so the lubrication matters for more, not less.
One myth that catches people out: if it starts and drives, it must be unharmed. A petrol motor fed diesel generally will not run, and so the motorist stops and the harm stops with them. Feed petrol to a diesel and it usually starts, ticks over and drives away as if nothing happened — all the while its pump wears. Running is not the same as fine.
Not so: a two-stroke additive lets you to drive home. It was an old fix, meant for another fault. What petrol has diluted stays diluted, and the petrol remains in your tank regardless.
"Drain it yourself and you're sorted" — a myth, because after it's been running some petrol lies in the filter and lines, waiting to go straight back through the pump at the next start. Clearing petrol into a can by the roadside is also really dangerous.
Petrol in a diesel: how does it happen?
A careless moment is rarely the cause, and no one means to do it. The forecourt makes it easy: the petrol nozzle is the smaller of the two, and it slips into a diesel filler with almost no resistance, whilst a diesel nozzle mostly will not go into a petrol vehicle at all. So the mistake runs one way.
The moment habit stops matching the car is the moment it happens. Any car that's new to you — hired, on loan as a courtesy car, or just bought. Households running one of each, petrol and diesel. Your usual forecourt, its pumps suddenly in a different order. Fuelling up in a rush en route to Bedford, with a train to catch. The first fill-up in a diesel Volkswagen Golf after years of driving petrol is precisely the moment it occurs. Your hand does what it has always done when you add rain, a phone call or a back seat full of kids.
Avoiding petrol in a diesel next time you fill up around Milton Ernest
- The label is what matters, and so check the pump rather than the colour: in the UK unleaded handles are usually green and diesel black, yet not on every forecourt.
- Inspect the filler flap. Many vehicles state the fuel type inside the flap or on the cap. Look at it on your first fill in any car you don't know.
- One of each in the household? Label the key to the diesel — a coloured fob, a sticker — since intending to remember isn't enough.
- Say it before you lift it. On your first fill in a new or hired car, say "diesel" out loud before you take the nozzle off the pump. It sounds silly and it works.
- Mistakes like this are easy to make while your mind is on something else, and so the phone goes away.
- Some diesels have 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 checking the pump.
- Spotting it halfway? Stop at once. A thinner mixture follows from less petrol inside your tank, but the next stage stays the same: do not crank it.
Milton Ernest: already put petrol in a diesel?
In that case, there is just a short order of things. Don't switch your ignition on, and do not fire it up. Yet at the forecourt, at Avon Drive Service Centre or anywhere else? Ask the staff to help you roll the car clear of the pump. What went in, roughly how much, and if it has run: tell us that when you phone 0333 366 0103.
If it was AdBlue instead of petrol, say so. That is a separate problem — corrosion and deposits and not lost lubrication — and it has its own page for Milton Ernest.
One petrol in a diesel job around Milton Ernest costs more than another. Why?
There is no fair single quote for this, since the four situations above are four different tasks. The situation itself does most of the work of moving your cost. Two things come after that: the petrol that was put in as a proportion of what your tank holds, then the place your car is in and whether our van can get to it safely.
Before any quote, not after, we ask three queries: the fuel that was put in, its quantity, and if it has run. That's why. The answers change a range into a straight figure.
About Milton Ernest and where it is
Milton Ernest is a village in Bedfordshire, situated on the banks of the River Great Ouse at an elevation of around 47 metres. Milton Ernest lies approximately 50 miles north of London and 14 miles east of Milton Keynes, with nearby villages including Radwell, Bletsoe, and Oakley. Milton Ernest has a population of around 770 people, predominantly living in detached houses.
Across Bedfordshire and in Milton Ernest: fuel drain cover
Radwell, Bletsoe and Oakley are among the places near Milton Ernest that the same vans work, answering petrol in diesel calls across Milton Ernest's MK postcode area. Our technicians drain wherever your vehicle is — your own driveway, a lay-by, a supermarket car park, a forecourt — so it does not have to come to us.
At the petrol pump around Milton Ernest, right now?
Nothing beats it: that is where you now are. Turned off it stays; then ring.