Petrol in a Diesel Car in Bourn: How Worried Should You Be?
Provided it has not been started, you can worry far less than you likely are. Till the ignition primes the pump, the starter cranks, or the vehicle is driven, petrol in a diesel tank just rests there and does no harm. Which means the truthful reply to the first Bourn question — "have I ruined it?" — usually no. Keep it like that: leave the motor off then call Petrol in Diesel. What petrol really does to a diesel, how to gauge how far it's gone, and how to keep it from happening again: that is the rest of this page.
What petrol in a diesel does to the motor
On its way through a motor, diesel does two jobs. Oiling comes before burning; it does both. Very fine clearances go into the injectors and the high-pressure fuel pump, and only the diesel flowing through keeps their surfaces from grinding together.
The second job petrol doesn't do at all, and the first it does poorly. A pump running on a petrol blend is wearing itself out, because petrol is runnier than diesel and takes away the lubrication your fuel system relies on. Petrol is also designed to resist igniting under compression — the opposite of what a diesel wants from its fuel — and that is where any clattering comes.
Put those together and the shape of the problem is clear. Not contact but movement is what causes the harm. A tank with petrol in it is a fuel issue. A pump that has been labouring on that petrol is the start of a mechanical one, and whatever a worn pump sheds travels on with your fuel to the injectors further on.
How serious is petrol in a diesel? Four situations we see around Bourn
Fuelled, and not started: no case is better. That petrol is inside the tank and just that tank, and the task is a drain and a flush where the vehicle stands. This is the one scenario that can only really take place at a forecourt, as anywhere else the car has been driven to get there.
Your ignition switched on, or a brief start. Once primed, the system has pulled petrol from that tank as far as the filter and the fuel lines. Still normally straightforward: drain, flush, and the filter seen to.
Your pump has spent a couple of miles on weakened fuel — that's what driving it does. Tank, lines, filter, then clean fuel put through the entire system: that is the work, and the way the car was driven counts as much as the mileage. On the school run to Bourn CofE Primary Academy, the miles is small. A run as far as Cambridge, under 10 miles away, is a very different job. So is any miles on the M11, under 10 miles from Bourn, where the engine has been labouring hard the whole time.
Driven until it complained. Knocking, a ragged idle, smoke, a throttle that has gone soft. The fuel isn't acting like diesel any more, and your motor is telling you. Leave it where it has stopped: a lay-by, a side street, the verge on Short Street. Permanent damage is very rare when a car is pulled over early, and the drain and flush-through that still go first deal with it.
What Bourn drivers get told about petrol in a diesel — and the stories in it
Myth: "Fill it the rest of the way with diesel and it will be fine." It will not. Topping up removes nothing; it gives you a bigger tank of the same mix. A diesel fuel system does not accept petrol by percentage in the way that guidance supposes.
If anything, the opposite holds. Myth: "A newer diesel can cope with a bit of petrol." At higher pressure, through finer components: that's how a modern diesel handles its fuel, and so the protection counts for more, not less.
Myth: "If it starts and drives, there is no harm done." This is the one that fools drivers. The motorist of a petrol motor fed diesel normally stops, because it will not run, and the damage stops there. A diesel fed petrol usually starts, idles and drives away as though nothing has happened, whilst your pump wears. Running isn't the same as fine.
Myth: "Add some two-stroke oil and drive it home." It's an old fix for a different issue. That petrol is still in that tank after that, and whatever it has thinned is not put back.
The next start sends petrol back round your pump out of the lines and the filter, where some of that sits once your engine has been run. That's why draining your tank yourself doesn't leave you sorted — a myth. Also, a can of petrol drained at the kerbside is truly dangerous.
Why petrol in a diesel takes place so easily
A careless moment is rarely the cause, and nobody means to do it. The forecourt makes it easy: the petrol nozzle is the narrower of the two, and it slips into a diesel filler with almost no resistance, whilst a diesel nozzle mostly won't go into a petrol car at all. So the error runs one way.
Habit and the vehicle getting out of step is how it happens. Any car that is new to you — hired, on loan as a courtesy car, or just bought. A household with one petrol and one diesel on the driveway. The pumps in a different order on a familiar forecourt. A hurried fill en route to Shepreth with a train to catch. The first fill-up in a diesel Renault Megane after years of driving petrol is precisely the moment it takes place. Add rain, a phone call or a back seat full of kids, and the hand repeats what it has always done.
How to avoid petrol in a diesel on your next fill-up around Bourn
- 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 motors state the fuel type inside the flap or on the cap. Look at it on your first fill in any motor you do not know.
- A coloured fob or a sticker on your diesel's key achieves more than any amount of meaning to remember, for a home with one of each.
- 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 petrol pump. It sounds daft and it works.
- Whilst you're thinking about something else, this is an easy mistake to make — so tuck your phone away.
- A misfuel inhibitor helps, up to a point. Some diesels have a filler built to reject a petrol nozzle, and add-on devices are available for motors without one. They are a backstop, not a reason to stop reading the pump.
- Stop as soon as you realise. Less petrol inside that tank makes a weaker mix. It does not change what to do next, which is still not to start the vehicle.
Put petrol in a diesel in Bourn already?
Then the order of things is short. Starting it is out, and so is switching on the ignition. Still on the forecourt, at Morrisons or anywhere else? Ask the attendants to help you roll it clear of the petrol pump. Call 0333 366 0103 next, with three facts — your fuel, the rough volume, and if it's run.
Say so if it was AdBlue instead of petrol: it's a separate issue, with its own page for Bourn, because AdBlue brings corrosion and deposits instead of lost protection.
One petrol in a diesel task around Bourn costs more than another. Why?
Four different tasks sit behind the four scenarios above — which is why there is no honest single price. What moves your cost is chiefly which of them you are in. Where the car is matters too, and whether our van can safely get to it, after the share of petrol to what the tank holds.
That is why our technicians ask three queries before quoting instead of after: what was put in, how much, and whether it's run. Those replies change a range into a straight figure.
About Bourn itself
Bourn is a village situated in the Cambridgeshire countryside, near the River Cam, with an elevation of around 48 metres. Bourn lies approximately 7.8 miles west of Cambridge and 47.3 miles north of London, making it a commuter village with a mix of old and new housing, predominantly detached homes. Bourn is surrounded by other small villages, including Crow End, Longstowe, and Caldecote, and has a population of around 1325 residents.
Fuel drain cover across Cambridgeshire, Bourn included
Petrol in diesel call-outs in Bourn — part of the CB postcode area — go to teams that also cover the places about it, Crow End, Longstowe and Caldecote included. The vehicle doesn't need to move to us: our engineers drain on a forecourt, in a supermarket car park, in a lay-by or on your own drive.
In Bourn and still at the pump?
Then, you could not be in a better position. Turned off it stays; then call.