How Worried Should You Be? Petrol in a Diesel Car in Thornhill
Less than you likely are, provided it has not been started. "Have I wrecked it?" is the first thing everyone in Thornhill asks, and the truthful answer is usually no, since petrol resting in a diesel tank hurts nothing till it is drawn through the fuel system — by ignition priming, by your starter, or by being driven. To leave the car that way, phone Petrol in Diesel and leave your engine alone. The rest of this page covers what petrol actually does to a diesel, how to judge how far it has got, and how to make sure it does not happen to you a second time.
Inside the engine: what petrol in a diesel really does
Diesel does two tasks on its way through an engine. It combusts, and before it combusts it protects. Your high-pressure pump and your injectors are designed to very fine clearances, and the diesel passing through them is what stops those surfaces from wearing against each other.
Poorly at the first, not at all at the second: that's petrol. The rattling 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 runnier than diesel, it strips away the lubrication the system depends on, and any pump working on such a mixture is wearing itself.
Put these together and the shape of the problem is plain. Contact doesn't do the damage — movement does. Where the petrol is only in that tank, it is an issue of fuel, nothing more. Whatever a worn pump sheds goes on, carried by your fuel, into your injectors downstream, which is why a pump that has worked on the petrol is where a mechanical fault begins.
Thornhill, petrol in a diesel: four situations, from mild to significant
Fuelled up, not once started. The best case there is. On a forecourt, and really only there, the petrol is still limited to the tank — since everywhere else the vehicle was driven to get to it. The job is emptying and rinsing on the spot.
Started for a second, or just your ignition on. The fuel system has been primed, and so petrol has left your tank and reached your filter and the fuel lines. Usually nothing more than draining, flushing and sorting your filter, so still simple.
A couple of miles driven, and your pump has spent each of them labouring on thinned fuel. Distance is only half of it; how hard it was driven matters equally. Either way the work includes that tank, the lines, the filter and clean fuel through the whole system. Driving the kids to Thornhill Junior and Infant School is one kind of trip. Very different again: a trip to Wakefield, under 10 miles away, or some mileage on the M1, under 3 miles from Thornhill, where the motor never stopped labouring hard.
It protested, and only then stopped: smoke, rattling, a throttle gone soft, an idle gone uneven. The fuel is not behaving like diesel any more, and your engine is telling you. Leave it wherever it has stopped: a lay-by, a quiet street, the verge on Frank Close. A car pulled over quickly very rarely has lasting damage, because the drain and the flush, which still come first, take care of it.
Stories Thornhill motorists hear about petrol in a diesel
It will not be fine. The myth: "Fill it the rest of the way with diesel and it will be." Topping up removes nothing; it gives you a bigger tank of the same mixture. A diesel fuel system does not tolerate petrol by percentage in the way that advice presumes.
"Newer diesels can handle a little petrol" — a myth, and closer to the reverse. A newer diesel sends its fuel through smaller parts at higher pressure, which makes the protection matter more, not less.
"It starts, it drives, and so there is no harm" — the myth that trips up more people than any other. Any petrol motor fed diesel normally will not run, so the driver stops and the damage stops with them. Feed petrol to a diesel and it usually fires up, ticks over and pulls away like nothing happened — all while its pump is wearing. Running is not 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 problem. What petrol has weakened remains thinned, and the petrol stays inside the tank regardless.
Once the motor has run, part of the petrol is in the filter and the lines, not that tank — and the next start sends it right back through the pump. So the myth "drain your tank yourself and you are sorted" doesn't stand up. Draining petrol into a can at the kerbside is also truly hazardous.
Why petrol in a diesel happens so easily
A careless moment is seldom the cause, and no one means to do it. The petrol nozzle is the smaller of the two and slips into a diesel filler with almost no resistance; a diesel nozzle mostly will not go into a petrol motor at all. The forecourt makes it easy, and the mistake runs one way.
It happens when routine and your car stop matching. A new vehicle, a hire car or a courtesy car. Two motors on one driveway, one petrol, one diesel. A familiar forecourt with the pumps in a different order. Fuelling up in a rush on the way to Ravensthorpe, with a train to catch. The first fill-up in a diesel Volkswagen Golf after years of driving petrol is exactly the moment it happens. Throw in a back seat full of kids, a phone call or rain, and habit wins.
How to prevent petrol in a diesel on your next fill-up in Thornhill
- Green for unleaded and black for diesel is normal in the UK — but not on each forecourt. Trust the label on the petrol pump, not the colour.
- Inspect the filler flap. Plenty of motors state the fuel type inside the flap or on the cap. Look at it on the first fill in any vehicle you don't know.
- One of each in the household? Mark the key to the diesel — a coloured fob, a sticker — since meaning to remember is not enough.
- Say it before you lift it. On the first fill in a new or hired car, say "diesel" out loud before you take the nozzle off the pump. It sounds daft and it works.
- Tuck your phone away. This is an easy mistake to make while you are thinking about something else.
- A misfuel inhibitor helps, up to a point. Some diesels have a filler built to block a petrol nozzle, and add-on devices exist for vehicles without one. They are a backstop, not a reason to stop reading the petrol pump.
- Stop as soon as you notice. Less petrol inside your tank makes a weaker mixture. It doesn't change what to do next, which is still not to start it.
Thornhill: already put petrol in a diesel?
In that case, there is only a short order of things. Leave it unstarted, with your ignition switched off as well. Ask the staff to help you push it clear of the petrol pump if you're still at the forecourt, whether that is bp or somewhere else. Then phone 0333 366 0103 and tell us what went in, roughly how much, and if it's run.
Say so if it was AdBlue instead of petrol: it is a separate issue, with its own page for Thornhill, since AdBlue brings corrosion and deposits instead of lost protection.
Thornhill petrol in a diesel tasks: why one costs more than another
Four different jobs lie behind the four scenarios above — which is why there is no honest single price. What shifts your cost is mostly which of them you are in. The ratio matters next, meaning how much of the tank is petrol, and then the position of the car and whether reaching it is safe for a van.
What went in, how much, and if it's run — three queries our engineers ask before pricing, not after, for exactly that reason. With the replies, you get a straight figure instead of a range.
About Thornhill and its setting
Thornhill is a suburban area in West Yorkshire, situated approximately 5 miles from Wakefield and 161 miles from London, at an elevation of around 104 metres. Thornhill sits inland, surrounded by nearby places such as Combs, Overthorpe, and Thornhill Edge, and is characterised by its predominantly semi-detached housing stock. Thornhill has a population of around 4355 residents, making it a modestly sized community in the region.
Thornhill and West Yorkshire: where our fuel drain cover runs
Petrol in diesel calls around Thornhill — part of the WF postcode area — go to vans that likewise cover the places round it, Combs, Overthorpe and Thornhill Edge included. A forecourt, a supermarket car park, a lay-by or your own drive are all places our engineers drain, and your car doesn't need to come to us.
Thornhill: still at the petrol pump?
Then, you could not be in a better place. Phone, and leave it switched off.