Swavesey: Petrol in a Diesel Car? How Worried to Be
Not started? Then less worried than you likely feel. "Have I wrecked it?" is the first thing anyone around Swavesey asks, and the honest answer is usually no, because petrol resting in a diesel tank harms nothing until it's drawn through your fuel system — by ignition priming, by the starter, or by driving. Leave the motor off then ring Petrol in Diesel — that is how you keep it like that. Keep reading for three things: the effect petrol has inside a diesel engine, the clues of how far it has got, and ways to make sure you never do it again.
Petrol in a diesel: what does it do to the engine?
Passing through a motor, diesel is doing two jobs at once. Before it combusts, it lubricates — and then it combusts. What stops the surfaces inside the high-pressure fuel pump and your injectors from wearing against each other is your diesel flowing through them — they are designed to very fine tolerances.
Petrol handles the first task poorly and the second not at all. The clattering comes from petrol being made not to ignite when compressed, which is precisely the opposite of what a diesel needs. On top of that it is runnier than diesel, it strips out the protection your system rests on, and any pump running on that blend is wearing itself.
Taken together, they show the shape the trouble takes. Contact does not do the damage — movement does. A tank with petrol in it is a fuel problem. The start of a mechanical one is a pump that has been running on that petrol — and whatever a worn pump sheds travels on with the fuel to your injectors beyond it.
Four situations our engineers see around Swavesey: how serious is petrol in a diesel?
Fuelled but never started — the best it gets. Just that tank has petrol in it, so the job is clearing your tank and flushing the system where the car stands. This scenario can only really occur on a forecourt: anywhere else, your car got there by being driven.
Your ignition turned on, or a short start. The fuel system has been bled, so petrol has left your tank and got to your filter and the fuel lines. That's normally still a simple job — a drain, a flush, and the fuel filter dealt with.
Your pump has worked a few miles on weakened fuel — that's what driving it does. How hard the car was driven counts as much as how far, and the work covers the tank, the lines, your filter and fresh fuel through the entire circuit. Short trips, such as the school run to Swavesey Primary School, are one thing. Very different a second time: a run to Cambridge, under 10 miles away, or some mileage on the M11, under 5 miles from Swavesey, where your engine never stopped running hard.
Driven on until it complained — clattering, smoke, an uneven idle, a soft throttle. That is the motor telling you its fuel has stopped behaving like diesel. Pull up wherever you are — the verge on Wallmans Lane, a lay-by, a side street — and leave it there. A car pulled over quickly very rarely has permanent damage, since the drain and the flush, which still come first, take care of it.
What Swavesey people get told about petrol in a diesel — and the stories in it
It will not be fine. The myth: "Fill it the rest of the way with diesel and it will be." Nothing is removed when you top up — that tank simply carries more of the same mixture. Percentage is not how a diesel fuel system copes with petrol, whatever that advice supposes.
If anything, the opposite is true. Myth: "A modern diesel can cope with a bit of petrol." Protection counts more on modern diesels, not less, since their fuel passes through finer components at higher pressure.
"It starts, it drives, and so there is no harm" — the myth that trips up most people than any other. Diesel in a petrol motor generally leaves a motor that won't run: the motorist stops, and so does the harm. While your pump grinds, a diesel fed petrol usually starts, idles and drives away as if nothing has happened. Running doesn't mean fine.
Myth: a two-stroke additive makes it safe to drive home. It is an old fix, meant for another issue. None of what petrol diluted is put back by it — and afterwards, the tank still contains the petrol.
"Drain it yourself and you're sorted" — a myth, since after it's been running some petrol lies in the filter and lines, ready to go right back through the pump on your next start. Besides, petrol cleared into a can by the road is genuinely hazardous.
Why petrol in a diesel happens so easily
On purpose? Never. Through carelessness? Seldom, if ever. The forecourt makes it easy: the petrol nozzle is the slimmer of the two, and it slides into a diesel filler with almost no resistance, whilst a diesel nozzle mostly won't go into a petrol motor at all. So the slip runs one way.
The moment habit stops matching the car is the moment it takes place. A new vehicle, a hire car or a courtesy car. Two cars on one drive, one petrol, one diesel. Your ordinary forecourt, its pumps suddenly in a different order. Fuelling up in a rush on the way to Huntingdon, with a train to catch. Precisely the moment it takes place: after years of driving petrol, someone fills a diesel Volkswagen Passat for the first time. Add 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 in Swavesey
- A green handle for unleaded and black for diesel is normal in the UK — yet not on each forecourt. Go by the label on the pump, not the colour.
- In a motor you do not know, look inside the flap over your filler or at the cap before your first fill: many cars print the fuel there.
- Good intentions count for less than a sticker or a fob in a vivid colour on your diesel's key if a house has one of each. So mark it.
- "Diesel", aloud, before you pick up the nozzle — each time a new or hired car gets its first tank. It sounds silly. It does the trick.
- Thinking about something else is when this becomes an easy mistake to make, and so put the phone away then keep your mind on the pump.
- Some diesels come with a filler built to refuse a petrol nozzle, and devices you can add exist for motors without one. Such an inhibitor helps up to a point — as a safety net, not a reason to stop reading the petrol pump.
- Stop as soon as you realise. Less petrol inside your tank makes a weaker mixture. It does not change what to do next, which is still not to crank it.
Petrol already in a diesel around Swavesey? Start here
The order of things is brief, then. Don't start it, and don't turn the ignition on. Ask the staff to help you roll it away from the petrol pump if you're still at the forecourt, whether that is Shell or somewhere else. Ring 0333 366 0103 next, with three facts — the fuel, the rough amount, and whether it has run.
Say so if it was AdBlue rather than petrol: it's a separate fault, with its own page for Swavesey, since AdBlue brings corrosion and deposits rather than lost lubrication.
Why one petrol in a diesel task around Swavesey costs more than another
A fair single quote does not exist here: four scenarios, four separate jobs. Which of them you are in is mostly what moves the cost. The proportion counts next, meaning how much of that tank is petrol, and then the position of the vehicle and whether getting to it is safe for a technician.
Before any quote, not after, come three questions: the fuel that went in, its quantity, and if it's run. That is why. A range becomes a straight figure once the answers are in.
About Swavesey and its setting
Swavesey is a village in Cambridgeshire, situated near lakes and low-lying wetlands, with an elevation of around 10 metres. Swavesey lies approximately 8.5 miles from Cambridge and 55.1 miles from London, making it a commuter village with a mix of old and new housing, predominantly detached homes. Swavesey has a population of around 1314 people and is surrounded by smaller settlements like Boxworth End and Over End.
Fuel drain cover across Cambridgeshire, Swavesey included
Boxworth End, Over End and Over are among the locations around Swavesey that the same vans work, answering petrol in diesel calls across Swavesey's CB postcode area. The vehicle doesn't need to move to us: our engineers drain at a forecourt, in a supermarket car park, in a lay-by or on your own driveway.
Swavesey: still at the pump?
Then, you could not be in a better place. Phone, and keep it turned off.