Elvet Hill: Petrol in a Diesel Car? How Worried to Be
Less than you likely are, provided it has not been started. Everyone around Elvet Hill starts with "have I wrecked it?", and the honest answer is generally no: petrol left inside your tank of a diesel stays harmless until priming, cranking or driving pulls it into the system. Keep it like that: leave your motor off and ring Petrol in Diesel. The rest of this page explains what petrol really does to a diesel, how to judge how far it has got, and how to make sure it does not happen to you again.
What petrol in a diesel does to the motor
On its way through an engine, diesel does two jobs. Oiling comes before burning; it does both. Very fine clearances are built into the injectors and your high-pressure pump, and only your diesel flowing through stops those surfaces grinding together.
The second job petrol does not do at all, and the first it does badly. The clattering comes from petrol being designed not to ignite when compressed, which is exactly the opposite of what a diesel needs. On top of that it is thinner than diesel, it strips away the protection the fuel system hinges on, and any pump working on that blend is wearing itself.
Together, those leave the shape of the issue clear. Not contact but circulation is what causes the damage. Where the petrol is only inside that tank, it is an issue of fuel, nothing more. Once your pump has been running on that petrol, a mechanical fault has begun: whatever is shed by a pump that is wearing travels downstream to your injectors with your fuel.
Four situations our technicians see in Elvet Hill: how serious is petrol in a diesel?
Filled up, and not started: no case is better. That petrol is inside your tank and only that tank, and the job is a drain and a flush where the vehicle sits. This is the one situation that can only truly take place on a forecourt, because anywhere else the vehicle has been driven to get there.
A moment's running, or merely the ignition on. With your system primed, the fuel lines and filter already contain petrol that came from the tank. That's generally still a straightforward task — a drain, a flush, and the filter seen to.
Driven a few miles. Now your pump has spent those miles working on diluted fuel. The work is your tank, the lines, the filter and fresh fuel through the entire circuit, and how hard your car was driven counts as much as how far. A school run to St Margaret's Church of England Primary School is one thing. Any miles on the A1(M), under 3 miles from Elvet Hill, means your engine has worked hard throughout, and a run to Durham, under a mile away, makes a very different job too.
Driven on until it protested — knocking, smoke, a ragged idle, a soft throttle. The motor is telling you the fuel is no longer behaving like diesel. Leave it wherever it stops: a lay-by, a side street, the verge on Almoners Barn. What goes first is still the drain and flush, and that deals with it, with long-term damage very rare when a car is stopped soon.
Stories Elvet Hill drivers hear about petrol in a diesel
Myth: "Fill it the rest of the way with diesel and it will be fine." It will not. Nothing is removed when you top up — the tank just carries more of the same mixture. That advice presumes a diesel fuel system tolerates petrol by percentage. It doesn't.
Not so: a modern diesel copes with a bit of petrol. Rather, the opposite. More precise components and higher pressure are the way a current diesel runs its fuel, and that makes the protection matter more, not less.
This is the one that catches motorists. Myth: "If it starts and drives, there's no damage done." Feed diesel to a petrol engine and it generally won't run, so the motorist stops — and the harm stops with them. Nothing looks to have happened when a diesel fed petrol fires up, ticks over and drives away, as it usually will; meanwhile the pump grinds. Running isn't the same as fine.
"A drop of two-stroke oil and drive it home" — a myth, taken from a fix from years ago, for a different fault. None of what petrol diluted gets put back by it — and later, your tank still holds that petrol.
"Drain it yourself and you're sorted" — a myth, since after it has been running some petrol lies in your filter and lines, ready to go right back through the pump at the next start. Besides, petrol drained into a can by the road is truly dangerous.
How does petrol in a diesel take place?
It is seldom carelessness, and nobody does it on purpose. One way only, because of the nozzles: the narrower petrol one slides inside a diesel filler with almost no resistance, whereas the diesel one mostly will not fit a petrol vehicle. That is how the forecourt makes it simple.
When routine and the vehicle stop matching, it happens. A new motor, a hire car or a courtesy car. Households running one of each, petrol and diesel. A forecourt you know, but with its pumps arranged differently. Fuelling up in a rush en route to Durham, with a train to catch. Precisely the moment it occurs: after years of driving petrol, a driver fills a diesel Renault Megane for the first time. Add a back seat full of children, a phone call or rain, and habit takes over.
Preventing petrol in a diesel next time you fill up in Elvet Hill
- Read the petrol pump, not the colour. In the UK unleaded handles are generally green and diesel black, but not on each forecourt. The label is what matters.
- Inspect the filler flap. Many cars state the fuel type inside the flap or on the cap. Look at it on your first fill in a car you do not know.
- Mark the key. In a house with one of each, a coloured fob or a sticker on your diesel's key does more than any amount of meaning to remember.
- "Diesel", out loud, before you lift the nozzle — every time a new or hired car needs its first tank. It sounds silly. It works.
- Mistakes like this are easy to make whilst your mind is on something else, and so the phone goes away.
- A misfuel inhibitor helps, up to a point. Some diesels have a filler designed to refuse a petrol nozzle, and add-on devices exist for cars without one. They are a safety net, not a reason to stop checking the petrol pump.
- Less petrol means a thinner mix, so stop as soon as you realise — while remembering that your next stage is unchanged. It is still not to crank it.
Elvet Hill: already put petrol in a diesel?
The order of things is brief, then. Don't start the vehicle, and do not switch your ignition on. Ask the staff to help you push it away from the pump if you are still at the forecourt, whether that's Shell or anywhere else. Then ring 0333 366 0103 and tell us what got in, about how much, and whether it's run.
Say so if it was AdBlue rather than petrol: it is a separate fault, with its own page for Elvet Hill, because AdBlue brings corrosion and deposits rather than lost lubrication.
One petrol in a diesel task in Elvet Hill costs more than another. Why?
There's no fair single price for this, because the four scenarios above are four different tasks. Mostly, your cost shifts with which one you are in. Where the car is counts too, and whether a van can safely get to it, after the proportion of petrol to what your tank takes.
What went in, how much, and whether it's run — three questions our technicians ask before pricing, not after, for exactly that reason. Given those answers, there is a straight figure rather than a range.
About Elvet Hill and where it is
Elvet Hill is a locality situated on the banks of the River Wear in County Durham, England, with a mix of detached housing and scenic riverside views. Elvet Hill lies close to the city of Durham, approximately 0.8 miles away, and is near other local places such as Lowes Barn and Nevilles Cross. Elvet Hill has a population of around 1924 residents and is characterised by its predominantly detached housing stock. Elvet Hill is located at an elevation of 103 metres above sea level, in a region known for its natural beauty and historic significance.
Elvet Hill and Durham: where our fuel drain cover runs
Elvet Hill rests in the DH postcode area, and our vans that answer petrol in diesel jobs there work the spots near it as well — Lowes Barn, Merryoaks and Nevilles Cross among them. We drain where the vehicle is — your own drive, a lay-by, a supermarket car park, a forecourt — so it never needs to come to us.
Still at the pump in Elvet Hill?
Nothing beats it: that is where you now are. Leave it turned off, then ring.