How Worried Should You Be? Petrol in a Diesel Car in Slaithwaite
If it has not been started, worry less than you likely are. "Have I ruined it?" is the first thing everyone around Slaithwaite asks, and the truthful answer is generally no, since petrol left in a diesel tank hurts nothing until it's drawn through the fuel system — by ignition priming, by the starter, or by driving. To leave it that way, ring Petrol in Diesel then leave your engine switched off. Below, you will find what petrol really does inside a diesel, how far it may have got, and how to stop it happening to you a second time.
Inside your engine: what petrol in a diesel does
On its way through a motor, diesel does two jobs. It combusts, and before it ignites it protects. Built to extremely fine tolerances, the injectors and the pump rely on the diesel flowing through them to stop their surfaces wearing against one another.
The second task petrol does not do at all, and the first it does badly. Being less viscous than diesel, petrol strips away the lubrication a fuel system needs, leaving a pump running on that mixture to wear itself. It is equally made to resist igniting under compression — the reverse of what a diesel needs — which is why you hear the clattering.
Together, those leave the shape of the problem plain. The damage is done by movement, not by contact. A tank with petrol in it is a fuel problem. The beginning of a mechanical problem is a pump that has been running on that petrol — and whatever a worn pump sheds travels on with your fuel to your injectors beyond it.
How bad is petrol in a diesel? Four scenarios our technicians see in Slaithwaite
Fuelled up, never started. The best case there is. The petrol is inside your tank and only the tank, and the job is a drain and a flush where the vehicle stands. This is the one scenario that can only really happen at a forecourt, because anywhere else your car has been driven to get there.
Ignition on, or started for a second. With the system primed, the lines and filter now contain petrol that has come from your tank. Still usually simple: drain, flush, and the filter sorted.
Those few miles on the road were your pump labouring on fuel weakened by petrol throughout. Miles is only half of it; how hard it was driven counts just as much. Either way the work includes the tank, your lines, your filter and clean fuel through the entire circuit. Short trips, like the school run to Nields Academy, are one matter. Very different a second time: a trip to Bradford, under 15 miles away, or any distance on the M62, under 3 miles from Slaithwaite, where the motor never stopped running hard.
Driven on till it protested — knocking, smoke, a lumpy idle, a dead throttle. What you are hearing is the engine signalling fuel that no longer runs like diesel. Whether it's the verge on Carr Lane, a lay-by or a side street, stop there then leave it. Lasting damage is very rare if a vehicle is stopped soon, and the fuel drain and flush that still go first sort it out.
What Slaithwaite people 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 takes out nothing; it gives you a bigger tank of the same mix. A diesel fuel system doesn't accept petrol by percentage in the way that guidance presumes.
If anything, the opposite is true. Myth: "A modern diesel can cope with a bit of petrol." A newer diesel runs its fuel through finer parts at higher pressure, which makes the lubrication count more, not less.
One myth that catches motorists off guard: if it starts and drives, it must be unharmed. Feed diesel to a petrol motor and it generally will not run, and so the driver stops — and the harm stops with them. Feed petrol to a diesel and it normally starts, idles and drives away like nothing happened — all while its pump is wearing. Running does not mean fine.
An old workaround for a distinct problem is behind this one. Myth: "Add some two-stroke oil and drive it home." The petrol is still in the tank afterwards, and whatever it has weakened isn't put back.
Myth: "Drain that tank yourself and you're sorted." Once your engine has run, some of that petrol is no longer inside the tank: it's in your filter and the fuel lines, and it goes straight back through the pump on the next start. And, a can of petrol filled at the roadside is genuinely hazardous.
Why petrol in a diesel happens at all
Nobody does it on purpose, and it's rarely carelessness. One way only, since of the nozzles: the slimmer petrol one slips inside a diesel filler with almost no resistance, whereas the diesel one generally will not fit a petrol vehicle. That's how the forecourt makes it straightforward.
When habit and the car stop matching, it happens. Any car that's new to you — hired, on loan as a courtesy car, or just bought. A household with one petrol and one diesel on the drive. The pumps in a different order on a familiar forecourt. A train to catch, and a rushed fill en route to the nearest station. Precisely the moment it takes place: after years of driving petrol, a driver fills a diesel Volkswagen Golf for the first time. With rain, a call arriving, or a car full of children to deal with, your hand simply does what it has always done.
Slaithwaite drivers: how to avoid petrol in a diesel next time
- Not every forecourt in the UK keeps to green for unleaded and black for diesel, even if most generally do. Check the pump's label; the colour is only a clue.
- The first fill in an unfamiliar motor is the time to check your filler flap — on it, or on the cap, plenty of vehicles state which fuel to use.
- Label your key. In a household with one of each, a coloured fob or a sticker on your diesel's key does more than any amount of meaning to remember.
- It sounds silly and it does the trick: on your first fill in a new or hired car, say "diesel" aloud before you lift the nozzle off the petrol pump.
- 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 come with a filler designed to block a petrol nozzle, and add-on devices are available for the remainder. Count it as a safety net, and keep checking the pump.
- Noticing it halfway? Stop there and then. A weaker mixture results from less petrol inside the tank, yet your next stage stays the same: do not fire it up.
Put petrol in a diesel in Slaithwaite already?
The order of things is brief, then. Do not switch your ignition on, and do not crank it. Yet at the forecourt, at the nearest petrol station or anywhere else? Ask the attendants to help you roll the vehicle away from the pump. Then ring 0333 366 0103 and tell us what went in, roughly how much, and whether it's run.
Say so if it was AdBlue instead of petrol: it's a different fault, with its own page for Slaithwaite, because AdBlue brings corrosion and deposits rather than lost lubrication.
What makes one Slaithwaite petrol in a diesel job cost more than the next
The four scenarios above are four separate tasks, so no single price for this would be honest. The situation itself does most of the work of moving the cost. The ratio counts next, meaning how much of that tank is petrol, followed by the position of the vehicle and whether getting to it is safe for a technician.
Three questions come first, before quoting, instead of after — what got in, how much, has it run — and that is the reason. With the answers, there is a straight figure rather than a range.
About Slaithwaite
Slaithwaite is a village in West Yorkshire, situated near several lakes and reservoirs, including those in the surrounding hills at an elevation of around 144 metres. Slaithwaite has a mix of housing types, but is predominantly characterised by terraced homes. Slaithwaite lies close to the nearby settlements of Hill Top, Blakestones, and Rotcher, and is within commuting distance of Bradford, which is approximately 12.5 miles away.
Slaithwaite and West Yorkshire: where our fuel drain cover runs
Our teams answering petrol in diesel jobs around Slaithwaite, in the HD postcode area, also work the locations around it, Hill Top, Blakestones and Rotcher among them. A forecourt, a supermarket car park, a lay-by or your own driveway are all places our engineers drain, and your vehicle does not need to move to us.
Still at the petrol pump in Slaithwaite?
Then you're in the best spot there is. Keep it turned off, and ring.