Bradshaw: Petrol in a Diesel Car? How Worried to Be
Less than you likely are, if it has not been started. "Have I ruined it?" is the first question everyone in Bradshaw asks, and the honest answer is generally no, since petrol resting in a diesel tank hurts nothing till it's dragged through the system — by ignition priming, by the starter, or by being driven. To keep it that way, phone Petrol in Diesel and leave your motor switched off. Below, this page sets out what petrol really does inside a diesel, how far it may have gone, and how to stop it happening to you a second time.
What petrol in a diesel does to the motor
On its way through a motor, diesel does two jobs. Before it combusts, it protects — then it ignites. The high-pressure fuel pump and your injectors are made to extremely fine clearances, and your diesel passing through them is what stops those surfaces from wearing against one another.
Petrol handles the first job badly and the second not at all. Being less viscous than diesel, petrol strips out the protection a fuel system needs, so a pump running on the blend wearing itself. It's equally made to resist igniting under compression — the opposite of what a diesel needs — which is why you hear the knocking.
Put these together and the shape of the trouble is plain. Contact does not do the damage — movement does. Where the petrol is only inside the tank, it is a problem of fuel, nothing more. 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 your injectors downstream.
How serious is petrol in a diesel? Four situations our technicians see in Bradshaw
Fuelled up, not once started. The best case there can be. On a forecourt, and really only there, the petrol is still confined to that tank — since anywhere else the vehicle was driven to get to it. The job is draining and cleaning on the spot.
Started for a second, or only the ignition on. Petrol has come out of that tank and reached the fuel filter and your lines, since the system has been bled. Still generally simple: drain, flush, and your filter sorted.
A few miles driven, and your pump has spent each of them running on thinned fuel. The work is that tank, your lines, the fuel filter and fresh fuel through the whole circuit, and how hard the vehicle was driven matters as much as how far. The school run to St Columba's RC Primary School is one thing. Very different again: a run to Salford, under 10 miles away, or some mileage on the St. Peter's Way, under 5 miles from Bradshaw, where your engine kept running hard.
Clattering, a lumpy idle, smoke, a throttle gone soft: driven until it complained. That's the motor telling you its fuel has stopped behaving like diesel. Leave it where it stops: a lay-by, a side street, the verge on Oaks Avenue. The drain and flush-through still come first, and they sort it out: when a vehicle is pulled over quickly, permanent damage is very uncommon.
Petrol in a diesel stories Bradshaw people hear
Myth: topping up to full with diesel makes it fine. It doesn't. Topping up takes out nothing; it gives you a fuller tank of the same mixture. A diesel fuel system does not tolerate petrol by percentage in the way that advice supposes.
If anything, the opposite holds. Myth: "A modern diesel can cope with a bit of petrol." A modern diesel sends its fuel through more precise parts at higher pressure, which makes the protection matter more, not less.
One myth that catches motorists off guard: if it starts and drives, it must be unharmed. Diesel in a petrol motor normally means a motor that will not run: the motorist stops, and so does the damage. Feed petrol to a diesel and it generally fires up, idles and pulls away like nothing has happened — all the while its pump wears. Running is not the same as fine.
Myth: "Add some two-stroke oil and drive it home." It's an old workaround for a different fault. It doesn't put back what petrol has diluted, and the petrol is still inside the tank later on.
"Drain it yourself and you are sorted" — a myth, since after it has been running some petrol sits in the fuel filter and lines, waiting to go straight back through your pump on the next start. Draining petrol into a can by the roadside is also really hazardous.
Petrol in a diesel: how does it happen?
It is rarely carelessness, and no one does it on purpose. The forecourt makes it easy: the petrol nozzle is the slimmer of the two, and it slips into a diesel filler with almost no resistance, whilst a diesel nozzle mostly will not go into a petrol motor at all. So the error runs one way.
Routine and the vehicle falling out of step is how it happens. A new car, a hire car or a courtesy car. One petrol and one diesel on the driveway of the same household. A forecourt you know, but with its pumps laid out differently. Racing for a train at Hall i' th' Wood and fuelling up en route. The first fill-up in a diesel Volkswagen Golf after years of driving petrol is exactly the moment it occurs. With rain, a call arriving, or a car full of children to deal with, the hand just does what it always has.
Next time you fill up in Bradshaw: preventing petrol in a diesel
- A green handle for unleaded and black for diesel is usual in the UK — but not on each forecourt. Go by the label on the petrol pump, not the colour.
- The first fill in a strange motor is the time to check your filler flap — on it, or on the cap, many motors state which fuel to use.
- Good intentions do less than a sticker or a fob in a vivid colour on the diesel's key when a household has one of each. So mark it.
- "Diesel", out loud, before you lift the nozzle — each time a new or hired car needs its first tank. It seems silly. It does the trick.
- Whilst you're thinking about something else, this is an easy mistake to make — so tuck the phone away.
- A misfuel inhibitor helps, up to a point. Some diesels come with a filler built to reject a petrol nozzle, and add-on devices are available for cars without one. They are a safety net, not a reason to stop checking the petrol pump.
- As soon as you realise, stop: less petrol in that tank makes a weaker mixture. What to do next doesn't change, though — still do not fire it up.
Put petrol in a diesel in Bradshaw already?
In that case, there is just a short order of things. Don't turn your ignition on, and don't start it. The staff on the forecourt — whether at Morrisons itself or wherever you filled up — will normally help push it away from the petrol pump if you ask. Next, 0333 366 0103. We'll ask what was put in, roughly how much, and if it has been run.
If it was AdBlue instead of petrol, say so. That's a separate problem — corrosion and deposits instead of lost lubrication — and it has its own page for Bradshaw.
Bradshaw petrol in a diesel jobs: why one costs more than another
There is no fair single price for this, because the four scenarios above are four separate tasks. Chiefly, your cost shifts with which one you are in. Where your car is counts too, and whether a technician can safely reach it, after the ratio of petrol to what that tank takes.
That's why our technicians ask three queries before pricing rather than after: what got in, how much, and whether it's run. The replies change a range into a straight figure.
About Bradshaw
Bradshaw is a suburban area in Greater Manchester, situated near the River Irwell and characterised by semi-detached housing. Bradshaw sits at an elevation of 116 metres, approximately 9.7 miles from Salford and 173.7 miles from London. Bradshaw is close to nearby places such as Bradshaw Chapel, Hall i th Wood, and Harwood Lee, and has a population of around 3309 residents.
Fuel drain cover across Greater Manchester, Bradshaw included
Petrol in diesel calls in Bradshaw — part of the BL postcode area — go to vans that likewise cover the spots about it, Bradshaw Chapel, Hall i th Wood and Harwood Lee included. A forecourt, a supermarket car park, a lay-by or your own drive are all places our engineers work, and your vehicle does not need to come to us.
In Bradshaw and still at the pump?
No position is better: that is where you are. Switched off it remains; then call.