Brownhills: Petrol in a Diesel Car? How Worried to Be
Probably less than you already are — as long as no one has started it. Everyone around Brownhills begins with "have I ruined it?", and the fair answer is normally no: petrol resting inside the tank of any diesel stays harmless until priming, cranking or driving draws it into your fuel system. To leave the vehicle like that, ring Petrol in Diesel then leave the engine alone. The remainder of this page explains what petrol actually does to a diesel, how to judge how far it has got, and how to make sure it doesn't happen to you a second time.
Petrol in a diesel: what does it do to your engine?
Two jobs fall to diesel on its route round a motor. Before it combusts, it protects — and then it ignites. What stops the surfaces inside your high-pressure pump and your injectors from grinding against one another is the diesel flowing through them — they're built to extremely fine clearances.
Of these two tasks, petrol manages the first poorly and the second not at all. It's runnier than diesel and strips away the protection the 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 clattering comes from.
Seen together, they make clear what shape the trouble takes. Not contact but movement is what causes the harm. Where that petrol is only inside your tank, it is an issue of fuel, nothing more. A pump that has been labouring on that petrol is the start of a mechanical one, and whatever a worn pump sheds moves on with the fuel to the fuel injectors downstream.
Four situations our technicians see in Brownhills: how serious is petrol in a diesel?
Fuelled but not once started — as good as it gets. At a forecourt, and genuinely only there, the petrol is still limited to that tank — because anywhere else the car was driven to get to it. The task is draining and cleaning on the spot.
A moment's running, or just the ignition on. Your system has been bled, so petrol has left your tank and got to your filter and the fuel lines. That is normally still an easy task — a drain, a flush, and the fuel filter dealt with.
Those few miles driven meant your pump running on fuel diluted by petrol throughout. Tank, lines, filter, then fresh fuel run through the whole circuit: that is the work, and the way the car was driven counts as much as the miles. The school run to St James Academy is one matter. Very different again: a trip to Lichfield, under 10 miles away, or some mileage on the M6 Toll, under 3 miles from Brownhills, where the engine never stopped working hard.
Driven until it protested. Rattling, an uneven idle, smoke, a throttle that has gone soft. What you are hearing is the engine reporting fuel that no longer acts like diesel. Leave it wherever it has stopped: a lay-by, a quiet street, the verge on High Street. Long-term damage is very uncommon if a car is pulled over early, and the drain and flush that still come first sort it out.
Brownhills motorists and that petrol in a diesel stories they hear
False: topping up to full with diesel makes it fine. It does not. A fuller tank of the same mixture is all you get, because topping up removes nothing. A diesel fuel system does not tolerate petrol by percentage in the way that guidance assumes.
Myth: a modern diesel copes with a bit of petrol. If anything, the reverse. Smaller components and higher pressure are the way a current diesel runs its fuel, and that makes the protection count more, not less.
"It starts, it drives, so there is no harm" — the myth that trips up most people than any other. The motorist of a petrol motor fed diesel usually has no choice but to stop, because it will not run, and the damage stops there. Whilst the pump wears, a diesel fed petrol usually starts, ticks over and drives away as though nothing has happened. Fine and running are not the same thing.
"A drop of two-stroke oil and drive it home" — a myth, borrowed from a fix from years ago, for a separate issue. It does not put back what petrol has weakened, and the petrol is still inside your tank later.
The next start sends petrol back round the pump from your lines and the fuel filter, where some of that ends up once the engine has run. That is why draining your tank yourself does not sort it — a myth. And, a can of petrol filled at the kerbside is truly dangerous.
Petrol in a diesel: how does it take place?
Nobody does it on purpose, and it is seldom carelessness. A diesel nozzle generally will not go into a petrol vehicle, yet the smaller petrol nozzle goes into the filler of a diesel almost without resistance — so forecourts make this one mistake simple, and just in that direction.
When habit and the vehicle stop matching, it happens. A new car, a hire car or a courtesy car. One petrol and one diesel on the driveway of the same household. A forecourt you know, but with its pumps laid out differently. A train to catch, and a rushed fill on the way to Shenstone. A new-to-you diesel Volkswagen Golf, its first fuelling, and a driver accustomed to petrol: exactly when it happens. Your hand does what it has always done when you add rain, a phone call or a back seat full of children.
Brownhills drivers: how to avoid petrol in a diesel next time
- Not every forecourt in the UK follows green for unleaded and black for diesel, though most usually do. Check the pump's label; the colour is just a clue.
- The first fill in an unfamiliar motor is the time to check the filler flap — on it, or on the cap, many motors state the fuel to use.
- 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.
- Before the nozzle leaves the petrol pump the first time you fuel a hired or new car, say "diesel" out loud. Silly, perhaps, yet it does the trick.
- Put the phone away. This is an easy mistake to make while you're thinking about something else.
- Some diesels have a filler built to refuse a petrol nozzle, and devices you can add are available for vehicles without one. Such an inhibitor helps up to a point — as a safety net, not a reason to stop reading the pump.
- Stop the moment you realise. Less petrol in that tank means a thinner blend. It does not change what to do next, which is still not to crank it.
Brownhills: already put petrol in a diesel?
The order of things is short, then. Leave it unstarted, with the ignition off too. Ask the staff to help you roll it away from the petrol pump if you're still on the forecourt, whether that is the nearest petrol station or anywhere else. Call 0333 366 0103 next, with three facts — your fuel, the rough quantity, and whether it's run.
AdBlue, not petrol? Then tell us. Corrosion and deposits, not lost lubrication, make it a separate fault — Brownhills has a page just for it.
What makes one Brownhills petrol in a diesel task cost more than the next
There is no fair single price for this, since the four situations above are four different jobs. The situation itself does most of the work of moving your cost. The proportion counts next, meaning how much of your tank is petrol, followed by the position of the car and whether reaching it is safe for a van.
What went in, how much, and whether it's run — three questions we ask before pricing, not after, for precisely that reason. A range becomes a straight figure when the answers are in.
About Brownhills and its setting
Brownhills is a town in the West Midlands, situated on the banks of the River Tame, with nearby settlements including Catshill, Clayhanger, and Shire Oak. Brownhills has a population of around 13867 people and is characterised by semi-detached housing. Brownhills is located near the city of Lichfield, approximately 5.1 miles away, and is about 109.7 miles northwest of London. Brownhills sits at an elevation of around 152 metres above sea level.
Fuel drain cover across West Midlands, Brownhills included
Catshill, Clayhanger and Shire Oak are among the places near Brownhills that the same teams work, answering petrol in diesel jobs across Brownhills's WS postcode area. The vehicle doesn't need to come to us: our technicians drain on a forecourt, in a supermarket car park, in a lay-by or on your own drive.
At the pump around Brownhills, still?
Then you are in the best spot there can be. Switched off it stays; then call.