How Worried Should You Be? Petrol in a Diesel Car in Craigerne
Unstarted? Then less anxious than you likely feel. Everyone around Craigerne starts with "have I wrecked it?", and the fair answer is normally no: petrol resting in that tank of any diesel stays harmless until priming, cranking or driving draws it into the fuel system. Petrol in Diesel is who to ring, with the engine kept off, and so it remains that way. Further down, 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.
Petrol in a diesel: what does it do to your engine?
On its way through a motor, diesel does two jobs. Before it combusts, it protects — then it burns. Extremely fine gaps go into the fuel injectors and the high-pressure pump, and just your diesel running through stops their surfaces grinding together.
The second task petrol doesn't do at all, and the first it does poorly. It is thinner than diesel and takes away the lubrication the fuel system hinges on, and so a pump running on a petrol mixture is a pump wearing itself. And petrol is made to resist igniting under compression, which is the opposite of what a diesel needs from its fuel. That's where the knocking comes from.
Taken together, they show the shape the issue takes. Contact doesn't do the harm — circulation does. Where that petrol is only inside your tank, it's a fault of fuel, nothing more. Whatever a worn pump sheds goes on, borne by the fuel, into your injectors further along, which is why a pump that has worked on the petrol is where a mechanical problem starts.
Petrol in a diesel in Craigerne: how bad is it? Four situations
Fuelled up, not once started. The best case there is. The petrol is inside that tank and just that tank, and the job is a drain and a flush where the vehicle stands. This is the one scenario that can only really occur at a forecourt, because anywhere else the vehicle has been driven to get there.
Ignition on, or started for a second. Once primed, the fuel system has pulled petrol from your tank up to the fuel filter and the lines. Drain, flush, deal with the filter: still normally easy.
Those few miles on the road meant the pump working on fuel thinned by petrol throughout. The work is that tank, the lines, the fuel filter and fresh fuel through the entire circuit, and how hard your car was driven matters as much as how far. Short trips, like the school run to the local primary school, are one matter. A run as far as Edinburgh, under 25 miles away, is a very different job. So is any miles on the M8, under 25 miles from Craigerne, where your engine has been working hard throughout.
Driven on until it complained — clattering, smoke, a lumpy idle, a dead throttle. That's your motor telling you its fuel no longer is acting like diesel. Pull up on the spot — on the verge on Glen Road, at the kerb, down a side road — and do not move it again. A car stopped soon very seldom has lasting damage, as the drain and the flush-through, which still go first, take care of it.
Petrol in a diesel stories Craigerne drivers hear
Myth: "Fill it the rest of the way with diesel and it'll be fine." It will not. Nothing is removed by topping up — you are left with a fuller tank, still the same mixture. That guidance supposes a diesel fuel system tolerates petrol by percentage. It doesn't.
If anything, the opposite is true. Myth: "A newer diesel can cope with a bit of petrol." More precise components and higher pressure are the way a current diesel runs its fuel, and that makes the protection count more, not less.
This is the one that catches motorists. Myth: "If it starts and drives, there is no harm done." Any petrol motor fed diesel generally will not run, and so the driver stops and the damage stops with them. Feed petrol to a diesel and it generally starts, ticks over and pulls away as if nothing happened — all the while its pump is wearing. Running isn't the same as fine.
An outdated fix for a different fault lies behind this one. Myth: "Add some two-stroke oil and drive it home." The petrol is still inside the tank after that, and whatever it has diluted isn't put back.
The next start sends petrol back round the pump from your lines and the filter, where some of that sits after the motor has run. That's why a DIY tank drain doesn't leave you sorted — a myth. On top of that, petrol drained into a can by the road is truly risky.
Petrol in a diesel: how does it occur?
It's rarely carelessness, and nobody does it on purpose. The petrol nozzle is the slimmer of the two and slides into a diesel filler with almost no resistance; a diesel nozzle generally won't go into a petrol vehicle at all. The forecourt makes it easy, and the error runs one way.
It occurs when habit and the vehicle stop matching. Courtesy car, hire car, or a motor that is new. One petrol and one diesel on the drive of the same household. A forecourt you know, but with its pumps laid out differently. A hurried fill en route to the nearest station with a train to catch. The first fill-up in a diesel Volkswagen Golf after years of driving petrol is precisely the moment it happens. The hand repeats what it has always done once you add rain, a phone call or a back seat full of kids.
Next time you fill up in Craigerne: preventing petrol in a diesel
- Green for unleaded and black for diesel is normal in the UK — yet not on each forecourt. Go by the label on the petrol pump, not the colour.
- Plenty of cars state the fuel type inside the filler flap or on the cap, and so check there on your first fill in any motor you don't know.
- One of each in the house? Label the key to your diesel — a coloured fob, a sticker — because intending to remember is not enough.
- "Diesel", aloud, before you pick up the nozzle — every time a new or hired car gets its first tank. It seems silly. It works.
- While you are thinking about something else, this is an easy mistake to make — so tuck the phone away.
- Up to a point, a misfuel inhibitor helps: some diesels have a filler designed to reject a petrol nozzle, and aftermarket devices exist for the remainder. Count it as a backstop, and keep checking the petrol pump.
- As soon as you notice, stop: less petrol in the tank makes a thinner blend. What to do next doesn't change, though — still don't start the car.
Petrol already in a diesel around Craigerne? Start here
Then, there's just a short order of things. Leave it unstarted, with the ignition switched off as well. If you are still on the forecourt — BP or anywhere else — ask the attendants to help you push the vehicle away from the pump. Next, 0333 366 0103. We will ask what was put in, about how much, and if it's been run.
Say so if it was AdBlue rather than petrol: it is a different fault, with its own page for Craigerne, because AdBlue brings corrosion and deposits instead of lost lubrication.
What makes one Craigerne petrol in a diesel task cost more than the next
There is no honest single price for this, because the four scenarios above are four separate jobs. What moves your cost is mostly which of them you are in. The ratio matters next, meaning how much of your tank is petrol, and then the position of your car and whether getting to it is safe for a technician.
Three queries come first, before quoting, instead of after — what was put in, how much, has it run — and that is the reason. Those answers are what turn a range into one firm number.
About Craigerne
Craigerne is a locality situated in a riverside setting in the Scottish Borders, with an elevation of 174 metres. Craigerne lies near several other small communities, including Kings Meadows and Kings Muir, and is located approximately 21 miles from Edinburgh. Craigerne has a mix of housing types, but terraced housing is predominant in the area. Craigerne is relatively small, with a population of around 1986 people.
Craigerne and Scottish Borders: where our fuel drain cover reaches
Kings Meadows, Kings Muir and Frankscroft are among the locations near Craigerne that the same vans work, answering petrol in diesel calls across Craigerne's EH postcode area. We drain where the car is — your own driveway, a lay-by, a supermarket car park, a forecourt — so it does not have to come to us.
Craigerne: still at the pump?
In that case, you couldn't be in a better position. Phone, and keep it turned off.