Should You Worry? Petrol in a Diesel Car in Roe Green
Far less than you probably are, provided it hasn't been started. Till the ignition primes your pump, the starter turns, or the car is driven, petrol in a diesel tank simply sits there and does nothing. Which makes the honest reply to the first Roe Green query — "have I ruined it?" — normally no. Leave the motor off and ring Petrol in Diesel — that keeps it like that. What petrol really does to a diesel, how to judge how far it's travelled, and how to stop it from happening again: that's the rest of this page.
Petrol in a diesel: what does it do to your engine?
Passing through an engine, diesel is doing two jobs at once. It lubricates to begin with, and after that does it burn. The high-pressure pump and the fuel injectors are designed to extremely fine tolerances, and your diesel passing through them is what stops those surfaces from grinding against each other.
Poorly at the first, not at all at the second: that is petrol. It is thinner than diesel and takes away the protection the fuel system depends on, and so a pump running on a petrol blend is a pump wearing itself. And petrol is made to resist igniting under compression, which is the reverse of what a diesel needs from its fuel. That's where the rattling comes from.
The shape of the issue is clear once you put those together. It's circulation that does the harm, not contact. Any tank with petrol in it is a fuel issue. Whatever a worn pump sheds travels on, carried by your fuel, into the injectors downstream, which is why a pump that has worked on that petrol is where a mechanical fault begins.
Roe Green, petrol in a diesel: four situations, from mild to major
Fuelled but not once started — as good as it gets. Being at a forecourt is what makes this the case: elsewhere, the car has been driven there to begin with. With that petrol held in that tank alone, it's drained and purged on the spot, and nothing more is needed.
A moment's running, or just your ignition on. With the system primed, the fuel lines and filter already hold petrol that came from the tank. Usually little more than emptying, rinsing and sorting the filter, so still straightforward.
Driven a couple of miles. Now your pump has spent those miles labouring on weakened fuel. Tank, lines, filter, then fresh fuel put through the whole circuit: that's the work, and the way your car was driven matters as much as the distance. Driving the children to Hatfield Community Free School is one kind of trip. Very different again: a trip to St Albans, under 5 miles away, or some mileage on the Hatfield Tunnel, under a mile from Roe Green, where the motor kept labouring hard.
Rattling, an uneven idle, smoke, a throttle gone soft: driven until it complained. That is your motor telling you its fuel no longer is behaving like diesel. Pull up wherever you are — the verge on The Common, a lay-by, a side street — and leave it where it is. Lasting damage is very unusual if a vehicle is pulled over quickly, and the fuel drain and flush-through that still come first deal with it.
Stories Roe Green drivers hear about petrol in a diesel
Myth: topping up to full with diesel makes it fine. It doesn't. Topping up takes out nothing; it gives you a bigger tank of the same mix. That guidance presumes a diesel fuel system tolerates petrol by percentage. It does not.
Myth: a current diesel copes with a bit of petrol. Rather, the reverse. Protection matters more on newer diesels, not less, because their fuel runs through finer components at higher pressure.
This is the one that catches drivers. Myth: "If it starts and drives, there is no harm done." Any petrol engine fed diesel generally won't run, and so the motorist stops and the damage stops with them. Feed petrol to a diesel and it generally fires up, ticks over and drives away as if nothing has happened — all the while its pump wears. Being able to run is not proof of being fine.
"A drop of two-stroke oil and drive it home" — a myth, taken from a fix from years ago, for a separate issue. The petrol is still in the tank afterwards, and whatever it has weakened is not put back.
The next start draws petrol back round the pump from the fuel lines and the fuel filter, where some of that ends up once the motor has run. That is why draining your tank yourself doesn't leave you sorted — a myth. And, a can of petrol drained by the kerbside is genuinely hazardous.
How does petrol in a diesel occur?
Carelessness is seldom the cause, and no one means to do it. The petrol nozzle is the narrower of the two and slides into a diesel filler with almost no resistance; a diesel nozzle generally won't go into a petrol vehicle at all. The forecourt makes it easy, and the mistake runs one way.
Habit and the car getting out of step is when it occurs. Hire cars, courtesy cars, and cars that are new to you. One petrol and one diesel on the driveway of the same household. A forecourt you know, only with its pumps laid out differently. A rushed fill en route to Hatfield with a train to catch. A new-to-you diesel Volkswagen Golf, its first fuelling, and a driver accustomed to petrol: exactly when it happens. Throw in a back seat full of children, a phone call or rain, and habit takes over.
Next time you fill up in Roe Green: avoiding petrol in a diesel
- Not every forecourt in the UK keeps to green for unleaded and black for diesel, even if most generally do. Check the petrol pump's label; the colour is just a clue.
- Many cars state the fuel inside the filler flap or on the cap, so check it on the first fill in any motor you don't know.
- A coloured fob or a sticker on your diesel's key achieves more than any amount of intending to remember, for a house with one of each.
- It sounds silly and it does the trick: on the first fill in a new or hired car, say "diesel" aloud before you take the nozzle off the petrol pump.
- Tuck the phone away. This is an easy mistake to make while you're thinking about something else.
- A misfuel inhibitor helps, up to a point. Some diesels come with a filler built to refuse a petrol nozzle, and add-on devices are available for cars without one. They are a backstop, not a reason to stop reading the petrol pump.
- Stop the moment you realise. Less petrol in the tank makes a thinner mix. It doesn't change what to do next, which is still not to crank it.
Roe Green: already put petrol in a diesel?
Then the order of things is brief. Leave it unstarted, with your ignition off too. Still at the forecourt, at Asda or anywhere else? Ask the staff to help you push the car away from the pump. Next, 0333 366 0103. We'll ask what went in, about how much, and if it has been run.
Say so if it was AdBlue rather than petrol: it's a separate problem, with its own page for Roe Green, because AdBlue brings corrosion and deposits instead of lost lubrication.
Why one petrol in a diesel job in Roe Green costs more than another
There's no fair single quote for this, because the four scenarios above are four separate jobs. Chiefly, your cost shifts with which one you're in. Where the car is matters too, and whether a van can safely get to it, after the share of petrol to what your tank takes.
Three questions come first, before any quote, instead of after — what got in, how much, has it run — and that is the reason. With the answers, there is a straight figure instead of a range.
About Roe Green and its setting
Roe Green is a suburban area in Hertfordshire, situated approximately 18 miles northwest of central London and 5 miles southeast of St Albans. Roe Green sits at an elevation of around 82 metres, in a gently sloping landscape of inland eastern England. Roe Green is characterized by a high proportion of flat dwellings, which dominate the local housing stock. Roe Green is close to nearby places such as Hatfield, Oxlease, and Birchwood, and is part of the wider commuter belt around London.
Across Hertfordshire and around Roe Green: fuel drain cover
Petrol in diesel calls in Roe Green — part of the AL postcode area — go to vans that likewise cover the places about it, Hatfield, Oxlease and Birchwood among them. Our technicians drain where the car is — your own drive, a lay-by, a supermarket car park, a forecourt — so it does not have to come to us.
Roe Green: still at the pump?
No position is better: that is where you are. Keep it off. Phone.