Penrose Hill: Petrol in a Diesel Car? How Worried to Be
If it has not been started, worry far less than you probably are. Petrol resting in a diesel tank does nothing to the engine until something draws it through the system — the ignition priming the pump, your starter, or the drive itself. So the truthful answer to the first query everyone around Penrose Hill asks, "have I wrecked it?", is normally no. To leave the vehicle that way, ring Petrol in Diesel then leave the engine switched off. The remainder of this page sets out 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.
Inside the motor: what petrol in a diesel does
Passing through a motor, diesel is doing two jobs at once. Before it ignites, it protects — and then it combusts. Very fine gaps go into your injectors and the high-pressure pump, and just the diesel flowing through keeps their surfaces from grinding together.
Of these two jobs, petrol handles the first badly and the second never. The clattering comes from petrol being designed not to ignite when compressed, which is exactly the reverse of what a diesel needs. On top of that it is thinner than diesel, it strips away the protection your system hinges on, and any pump working on that mixture is wearing itself.
Seen together, they show what shape the problem has. Not contact but circulation is what causes the harm. A tank with petrol in it is a fuel issue. Whatever a worn pump sheds travels on, carried by the fuel, into the injectors further along, which is why a pump that has worked on that petrol is where a mechanical issue begins.
Penrose Hill, petrol in a diesel: four situations, from mild to major
Fuelled up, never started. The best case there is. That petrol is in that tank and only the tank, and the task is a drain and a flush where your car stands. This is the one situation that can only truly occur at a forecourt, as anywhere else the vehicle has been driven to get there.
The ignition switched on, or a brief start. With your system primed, the fuel lines and filter now contain petrol that has come from the tank. Usually nothing more than clearing, cleaning and sorting your filter, and so still straightforward.
Driven a few miles. Now your pump has spent those miles working on thinned fuel. How hard the car was driven counts as much as how far, and the work takes in your tank, the fuel lines, your filter and fresh fuel through the whole circuit. Driving the kids to Porthleven School is one sort of trip. Very different once more: a run to Truro, under 25 miles away, or some miles on the M5, over 50 miles from Penrose Hill, where the engine never stopped working hard.
Driven until it protested. Clattering, an uneven idle, smoke, a throttle that has gone soft. The fuel isn't acting like diesel any more, and the motor is telling you. Leave it wherever it has stopped: a lay-by, a quiet street, the verge on Green Lane. A vehicle stopped quickly very seldom has lasting damage, as the fuel drain and the flush, which still go first, deal with it.
Petrol in a diesel stories Penrose Hill motorists hear
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 mixture. Percentage isn't how a diesel fuel system tolerates petrol, however much that guidance supposes.
If anything, the reverse is true. Myth: "A modern diesel can cope with a bit of petrol." Finer components and higher pressure are the way a modern diesel runs its fuel, and that makes the protection count more, not less.
Myth: "If it starts and drives, there is no damage done." This is the one that catches people. Feed diesel to a petrol engine and it normally will not run, and so the driver stops — and the damage stops with them. Whilst the pump wears, a diesel fed petrol usually starts, ticks over and drives away as though nothing has happened. Running isn't the same as fine.
Myth: "Add some two-stroke oil and drive it home." It's an outdated workaround for a separate problem. That petrol is still in your tank after that, and what it has weakened is not put back.
Myth: "Drain your tank yourself and you're sorted." Once your engine has run, some of the petrol is no longer in that tank: it is in your filter and your lines, and it goes right back through the pump at your next start. Draining petrol into a can at the kerbside is also truly dangerous.
Why petrol in a diesel occurs so easily
On purpose? Never. Through carelessness? Rarely, if ever. A diesel nozzle generally will not fit a petrol motor, but the narrower petrol nozzle goes into the filler of a diesel nearly without resistance — so forecourts make this one error straightforward, and only in one direction.
Habit and the car falling out of step is when it happens. A vehicle that's new to you — hired, on loan as a courtesy car, or brand new. One petrol and one diesel on the driveway of the same household. A forecourt you know, only with its pumps arranged differently. Fuelling up in a hurry en route to St Erth, with a train to catch. Years of petrol vehicles behind you, a diesel Volkswagen Golf in front of you at the forecourt for its first tank — that's when. Throw in rain, a phone call or a back seat full of kids, and your hand does what it has always done.
Avoiding petrol in a diesel next time you fill up around Penrose Hill
- Check the petrol pump, not the colour. In the UK unleaded handles are generally green and diesel black, yet not on every forecourt. The label is what counts.
- In a motor you do not know, look inside the flap over the filler or at the cap before your first fill: many cars state the fuel type there.
- A coloured fob or a sticker on the diesel's key does more than any amount of intending to remember, for a house with one of each.
- Before the nozzle leaves the pump the first time you fuel a hired or new car, say "diesel" aloud. Silly, yes, but it works.
- Put the phone away. This is an easy mistake to make whilst you are thinking about something else.
- Some diesels have a filler designed 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 backstop, not a reason to stop reading the petrol pump.
- Less petrol makes a thinner mix, so stop the moment you realise — though remembering that the next step is unchanged. It's still not to fire it up.
Petrol already in a diesel around Penrose Hill? Start here
Short and simple, then, is the order of things. Starting it is out, and so is switching on your ignition. Ask the attendants to help you roll it clear of the petrol pump if you are still on the forecourt, whether that's Pace or somewhere else. Next, 0333 366 0103. We will ask what was put in, about how much, and if it has been run.
If it was AdBlue instead of petrol, say so. That is a different problem — corrosion and deposits and not lost protection — and it has its own page for Penrose Hill.
Penrose Hill petrol in a diesel tasks: why one costs more than another
The four situations 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. The share matters next, meaning how much of your tank is petrol, followed by the position of the car and whether getting to it is safe for a van.
What went in, how much, and if it has run — three queries we ask before pricing, not after, for precisely that reason. With those answers, there is a straight figure instead of a range.
About Penrose Hill and where it is
Penrose Hill is a coastal locality in Cornwall, situated near the town of Porthleven and overlooking the sea. Penrose Hill sits at an elevation of 67 metres, with detached housing being the predominant type of accommodation in the area. Penrose Hill is located near other small settlements such as Degibna and Sithney Common, and is approximately 16 miles from the city of Truro. Penrose Hill has a population of around 705 people, making it a small but distinct community in the region.
Penrose Hill and Cornwall: where our fuel drain cover runs
Our vans answering petrol in diesel call-outs in Penrose Hill, in the TR postcode area, also work the places around it, Porthleven, Degibna and Sithney Common included. No need to bring your vehicle to us. Forecourts, supermarket car parks, lay-bys and your own drive are all spots where we work.
At the petrol pump around Penrose Hill, still?
Nothing beats it: that's where you are. Switched off it stays; then ring.