Sharmans Cross: Petrol in a Diesel Car? How Worried to Be
Less than you probably are, if it hasn't been started. Petrol resting in a diesel tank does nothing to your motor till something pulls it through your fuel system — your ignition priming the pump, your starter, or the drive on its own. So the honest answer to the first query anyone in Sharmans Cross asks, "have I ruined it?", is generally no. Keep it like that: leave your motor off then ring Petrol in Diesel. What petrol really does to a diesel, how to gauge how far it's travelled, and how to keep it from happening a second time: that is the remainder of this page.
What petrol in a diesel does to the engine
Two jobs fall to diesel on its journey through a motor. Lubricating comes before burning; it does both. Very fine tolerances are built into the fuel injectors and your high-pressure pump, and just your diesel flowing through keeps their surfaces from grinding together.
The second job petrol doesn't do at all, and the first it does badly. A pump running on a petrol blend is wearing itself out, because petrol is thinner than diesel and strips out the lubrication the fuel system depends on. Petrol is also designed to resist igniting under compression — the reverse of what a diesel needs from its fuel — and that's where any rattling starts.
Put those together and the shape of the trouble is plain. The damage is done by movement, not by contact. A tank with petrol in it is a fuel issue. Whatever a worn pump sheds travels on, carried by the fuel, into your injectors downstream, which is why a pump that has worked on the petrol is where a mechanical problem begins.
How bad is petrol in a diesel? Four scenarios our engineers see in Sharmans Cross
The best case there is: filled up, not once started. At a forecourt, and genuinely only there, the petrol is still limited to your tank — since everywhere else the vehicle was driven to reach it. The job is draining and rinsing on the spot.
Ignition on, or started for a second. Your system has been primed, so petrol has left the tank and got to the fuel filter and your lines. Normally nothing more than emptying, rinsing and sorting your filter, and so still easy.
Some miles driven, and the pump has spent each of them labouring on weakened fuel. Tank, lines, filter, then fresh fuel run through the entire system: that's this work, and the way your car was driven counts as much as the mileage. On the school run to Sharmans Cross Junior School, the miles is small. Getting as far as Birmingham, under 10 miles away, makes a very different job — as does any distance on the M42, under 3 miles from Sharmans Cross, with the engine running hard the whole time.
Knocking, a lumpy idle, smoke, a throttle gone soft: driven until it complained. That's your motor telling you its fuel no longer is acting like diesel. Pull up wherever you are — the verge on Sharmans Cross Road, a lay-by, a side street — and leave the vehicle where it is. What goes first is still the fuel drain and flush-through, and that takes care of it, with long-term damage very unusual if a vehicle is stopped soon.
Sharmans Cross motorists and that petrol in a diesel stories they hear
Myth: topping up to full with diesel makes it fine. It doesn't. Nothing is removed when you top up — that tank simply carries more of the same blend. The assumption behind the advice — that diesel fuel systems tolerate petrol by percentage — is wrong.
Myth: "A modern diesel can cope with a bit of petrol." If anything, the reverse. A modern diesel sends its fuel through more precise parts at higher pressure, which makes the lubrication matter more, not less.
The myth that catches drivers off guard: if it starts and drives, it must be unharmed. The motorist of a petrol engine fed diesel normally stops, because it will not run, and the damage stops with them. A diesel fed petrol usually starts, ticks over and drives away as though nothing has happened, while your pump grinds. Running isn't the same as fine.
An outdated workaround for a separate issue lies behind this one. Myth: "Add some two-stroke oil and drive the vehicle home." It does not put back what petrol has thinned, and that petrol is still in that tank after that.
"Drain it yourself and you're sorted" — a myth, since after it's been running some petrol lies in the fuel filter and lines, waiting to go right back through your pump on the next start. Besides, petrol emptied into a can by the road is genuinely hazardous.
Petrol in a diesel: how does it happen?
Carelessness is rarely the cause, and no one means to do it. The forecourt makes it simple: the petrol nozzle is the slimmer of the two, and it slides into a diesel filler with almost no resistance, while a diesel nozzle generally won't go into a petrol vehicle at all. So the mistake runs one way.
Routine and the vehicle falling out of step is how it takes place. Courtesy car, hire car, or a motor that is brand new. A household with one petrol and one diesel on the drive. The pumps in a different order on a well-known forecourt. A train to catch, and a hurried fill on the way to Solihull. The first fill-up in a diesel Volkswagen Passat after years of driving petrol is exactly the moment it happens. Throw in rain, a phone call or a back seat full of children, and your hand does what it has always done.
Avoiding petrol in a diesel next time you fill up in Sharmans Cross
- A green handle for unleaded and black for diesel is normal in the UK — but not on every forecourt. Trust the label on the pump, not the colour.
- Inspect the filler flap. Many vehicles state the fuel type inside the flap or on the cap. Look at it on the first fill in any vehicle you do not know.
- Label your key. In a house with one of each, a coloured fob or a sticker on the diesel's key does more than any amount of meaning to remember.
- 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 seems daft and it does the trick.
- Mistakes like this are simple to make while your mind is on something else, and so the phone goes away.
- Some diesels come with a filler built to reject a petrol nozzle, and devices you can add are available for cars without one. Such an inhibitor helps up to a point — as a backstop, not a reason to stop reading the petrol pump.
- Stop as soon as you notice. Less petrol in the tank means a weaker mix. It does not change what to do next, which is still not to fire it up.
Petrol already in a diesel in Sharmans Cross? Start here
The order of things is short, then. Starting it is out, and so is switching on your ignition. Ask the staff to help you push it away from the pump if you're still at the forecourt, whether that's BP or somewhere else. What got in, about how much, and whether it has run: tell us those when you call 0333 366 0103.
If it was AdBlue instead of petrol, say so. That's a separate fault — corrosion and deposits instead of lost lubrication — and it has its own page for Sharmans Cross.
Why one petrol in a diesel job around Sharmans Cross costs more than another
The four scenarios above are four separate jobs, so no single quote for this would be honest. The situation itself does most of the work of moving your cost. Where your car is matters too, and whether our van can safely get to it, after the proportion of petrol to what that tank holds.
Three queries come first, before quoting, instead of after — what went in, how much, has it run — and this is the reason. The replies turn a range into a straight figure.
About Sharmans Cross and its setting
Sharmans Cross is a suburban area in the West Midlands, situated approximately 6 miles south of Birmingham city centre. Sharmans Cross sits at an elevation of around 140 metres, with detached housing being the predominant type of accommodation in the area. Sharmans Cross is close to nearby places such as Blossomfield and Shirley, and is about 95 miles northwest of London.
Fuel drain cover in Sharmans Cross and across West Midlands
The vans answering petrol in diesel call-outs around Sharmans Cross, in the B postcode area, equally work the spots near it, Blossomfield, Shirley Street and Shirley included. The vehicle does not need to move to us: our technicians drain on a forecourt, in a supermarket car park, in a lay-by or on your own drive.
In Sharmans Cross and still at the pump?
The best place there is, then — that's where you are. Keep it off. Call.