How Worried Should You Be? Petrol in a Diesel Car in Stokenchurch
Less than you probably are, provided it has not been started. "Have I ruined it?" is the first thing anyone in Stokenchurch asks, and the truthful answer is generally no, because petrol left in a diesel tank harms nothing until it is drawn through the fuel system — by ignition priming, by your starter, or by being driven. Leave your motor off then ring Petrol in Diesel — that is how you keep it that way. Read on for three things: the effect petrol has inside a diesel motor, 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 motor?
Passing through a motor, diesel is doing two jobs at once. Oiling comes before burning; it does both. The high-pressure fuel pump and your injectors are designed to very fine clearances, and the diesel passing through them is what keeps those surfaces from wearing against one another.
The second job petrol doesn't do at all, and the first it does badly. Being less viscous than diesel, petrol strips away the protection a fuel system needs, so a pump running on that mixture to wear itself. It's equally made to resist igniting under compression — the reverse of what a diesel needs — which is where you hear the clattering.
Taken together, they show the shape the issue takes. Contact doesn't do the harm — movement does. Where the petrol is only in 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 the fuel to the injectors further on.
Four scenarios our technicians see in Stokenchurch: how bad is petrol in a diesel?
Filled up, and never started: no case is better. That petrol is in that tank and only your tank, and the job is a drain and a flush where the car stands. This is the one situation that can only truly happen on a forecourt, as anywhere else the vehicle has been driven to get there.
Ignition on, or started for a moment. The fuel system has been primed, so petrol has left the tank and reached the filter and the lines. That is usually still a straightforward job — a drain, a flush, and the filter seen to.
A few miles driven, and the pump has spent every one of them labouring on thinned fuel. How hard the car was driven matters as much as how far, and the work takes in the tank, the fuel lines, the fuel filter and clean fuel through the whole system. A school run to Stokenchurch Primary School is one thing. A run as far as Oxford, under 25 miles away, is a very different task. So is any mileage on the M40, under a mile from Stokenchurch, where your engine has been working hard throughout.
It protested, and only then stopped: smoke, rattling, a throttle gone soft, an idle gone uneven. The engine is telling you your fuel is no longer acting like diesel. Stop on the spot — on the verge on The Common, at the kerb, down a side road — and do not move it again. A car pulled over quickly very seldom has permanent damage, as the drain and the flush, which still come first, sort it out.
What Stokenchurch motorists get told about petrol in a diesel — and the stories in it
Myth: "Fill it the rest of the way with diesel and it'll be fine." It will not. A fuller tank of the same mix is all you get, since topping up removes nothing. A diesel fuel system does not tolerate petrol by percentage in the way that advice presumes.
Myth: "A current diesel can cope with a bit of petrol." If anything, the reverse. Smaller parts and higher pressure are how a modern diesel runs its fuel, and that makes the protection matter more, not less.
Myth: "If it starts and drives, there is no damage done." This is the one that fools people. The driver of a petrol engine fed diesel usually stops, since it will not run, and the damage stops with them. Feed petrol to a diesel and it normally fires up, idles and drives away like nothing has happened — all while its pump is wearing. Running doesn't mean fine.
Myth: "Add some two-stroke oil and drive the car home." It's an old workaround for a different issue. The petrol is still in the tank afterwards, and whatever it has thinned is not put back.
If the engine has run, part of that petrol is in the filter and the fuel lines, not that tank — and your next start sends it straight back through the pump. So the myth "drain the tank yourself and you are sorted" does not stand up. It is also truly dangerous to drain petrol into a can at the roadside.
Petrol in a diesel: how does it take place?
It's rarely carelessness, and nobody does it on purpose. The petrol nozzle is the slimmer of the two and slips into a diesel filler with almost no resistance; a diesel nozzle generally won't go into a petrol motor at all. The forecourt makes it simple, and the mistake runs one way.
It takes place when habit and your car stop matching. Courtesy car, hire car, or a motor that's new. Two cars on one driveway, one petrol, one diesel. A forecourt you know, but with its pumps laid out differently. A rushed fill en route to Saunderton with a train to catch. A new-to-you diesel Renault Megane, its first fuelling, and a motorist accustomed to petrol: exactly when it happens. Your hand does what it has always done once you add rain, a phone call or a back seat full of children.
Preventing petrol in a diesel next time you fill up around Stokenchurch
- Not every forecourt in the UK keeps to green for unleaded and black for diesel, even if most generally do. Read the petrol pump's label; the colour is only a clue.
- The first fill in an unfamiliar car is the time to check the filler flap — on it, or on the cap, plenty of motors state which fuel they take.
- 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.
- Say it before you lift it. On your first fill in a new or hired car, say "diesel" aloud before you lift 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.
- Up to a point, a misfuel inhibitor helps: some diesels come with a filler designed to refuse a petrol nozzle, and add-on devices are available for the remainder. Count it as a safety net, then keep checking the petrol pump.
- The moment you realise, stop: less petrol in your tank makes a weaker mixture. What to do next doesn't change, though — still do not fire it up.
Petrol already in a diesel in Stokenchurch? Begin here
Short and simple, then, is the order of things. Do not switch the ignition on, and don't start it. Ask the attendants to help you roll it away from the pump if you're still at the forecourt, whether that is Shell or somewhere else. What got in, roughly how much, and if it's run: tell us those when you phone 0333 366 0103.
Say so if it was AdBlue rather than petrol: it's a separate issue, with its own page for Stokenchurch, because AdBlue brings corrosion and deposits instead of lost lubrication.
One petrol in a diesel job in Stokenchurch costs more than another. Why?
The four scenarios above are four separate jobs, so no single quote for this would be fair. Which of them you're in is mostly what moves the cost. Where your car is matters too, and whether a van can safely get to it, after the ratio of petrol to what the tank holds.
What got in, how much, and whether it's run — three queries we ask before pricing, not after, for exactly that reason. The answers turn a range into a straight figure.
About Stokenchurch, for a moment
Stokenchurch is a village in Buckinghamshire, situated in the Chiltern Hills at an elevation of 227 metres. Stokenchurch lies approximately 34.9 miles west of London and 16.5 miles southeast of Oxford, near the villages of Waterend and Sprigs Alley. Stokenchurch has a population of around 1340 people, predominantly living in terraced housing. Stokenchurch is surrounded by rolling countryside, including the nearby Crowell Hill.
Across Buckinghamshire and around Stokenchurch: fuel drain cover
Stokenchurch sits in the HP postcode area, and the vans that answer petrol in diesel call-outs there work the places around it as well — Waterend, Sprigs Alley and Crowell Hill among them. The car doesn't need to come to us: our technicians drain at a forecourt, in a supermarket car park, in a lay-by or on your own drive.
Still at the petrol pump in Stokenchurch?
The best spot there is, then — that's where you are. Phone, and keep it switched off.