How Worried Should You Be? Petrol in a Diesel Car in Trench
Likely less than you are now — provided nobody has started the vehicle. Until your ignition primes the pump, the starter cranks, or the vehicle is driven, petrol in a diesel tank simply sits there and does no harm. Which means the honest reply to the first Trench question — "have I wrecked it?" — usually no. Petrol in Diesel is who to call, with your motor kept off, and so it remains that way. The remainder of this page sets out what petrol really does to a diesel, how to tell how far it has got, and how to make sure it doesn't happen to you again.
What petrol in a diesel does to the motor
On its way through a motor, diesel does two jobs. It burns, and before it burns it lubricates. Made to very fine tolerances, the injectors and the pump depend on your diesel flowing through them to stop their surfaces wearing against one another.
Petrol does the first job badly and the second not at all. Being less viscous than diesel, petrol strips away the lubrication a fuel system needs, so a pump running on the mixture wearing itself. It's equally made to resist igniting under compression — the reverse of what a diesel needs — which is why you get the rattling.
The shape of the trouble is plain when you put those together. Not contact but circulation is what causes the harm. Petrol in the tank is a fuel problem. The start of a mechanical one is a pump that has been running on that petrol — and whatever a worn pump sheds travels on with the fuel to the fuel injectors beyond it.
Petrol in a diesel around Trench: how bad is it? Four situations
Filled but never started — the best it gets. Being at a forecourt is what makes this possible: elsewhere, the vehicle has been driven there to begin with. With that petrol held in the tank alone, it is cleared and purged right where it stands, and nothing more is needed.
Your ignition turned on, or a short start. Your system has been bled, so petrol has left the tank and reached the fuel filter and your lines. Still usually simple: drain, flush, and the filter dealt with.
A couple of miles driven, and the pump has spent every one of them labouring on thinned fuel. Tank, lines, filter, then fresh fuel put through the entire system: that is this work, and the way the vehicle was driven counts as much as the distance. Driving the children to St Luke's Catholic Primary School, a Voluntary Academy. is one sort of trip. A run as far as Wolverhampton, under 25 miles away, is a very different task. So is any miles on the M54, under 3 miles from Trench, where your engine has been working hard throughout.
Clattering, a lumpy idle, smoke, a throttle gone soft: driven till it complained. The engine is telling you your fuel is no longer acting like diesel. Stop wherever you are — the verge on Bridge Close, a lay-by, a side street — then leave the vehicle where it is. The fuel drain and flush still go first, and they take care of it: when a car is pulled over quickly, long-term damage is very uncommon.
Trench people and that petrol in a diesel stories they hear
Myth: "Fill it the rest of the way with diesel and it'll be fine." It will not. Topping up removes nothing; it gives you a bigger tank of the same mix. That guidance presumes a diesel fuel system handles petrol by percentage. It does not.
Myth: "A newer diesel can cope with a bit of petrol." If anything, the reverse. A modern diesel sends its fuel through more precise components at higher pressure, which makes the protection matter more, not less.
"It starts, it drives, so no harm done" — the myth that catches most motorists than any other. Feed diesel to a petrol motor and it usually will not run, so the driver stops — and the damage stops with them. A diesel fed petrol normally starts, idles and drives away as if nothing has happened, whilst the pump grinds. Fine and running aren't the same at all.
Myth: "Add some two-stroke oil and drive the vehicle home." It is an old fix for a different issue. That petrol is still in the tank afterwards, and what it has weakened is not put back.
Once the engine has run, part of that petrol sits in the filter and the lines, not your tank — and the next start pulls it straight back through the pump. So the myth "drain that tank yourself and you're sorted" doesn't stand up. Also, a can of petrol drained by the roadside is genuinely dangerous.
Why petrol in a diesel happens so easily
A careless moment is rarely the cause, and no one means to do it. One way only, since of the nozzles: the smaller petrol one slips inside a diesel filler with almost no resistance, while the diesel one mostly will not fit a petrol vehicle. That is how the forecourt makes it easy.
Habit and the vehicle falling out of step is when it happens. Courtesy car, hire car, or a vehicle that's new. A household with one petrol and one diesel on the drive. A familiar forecourt with the pumps in a different order. Fuelling up in a rush on the way to Oakengates, with a train to catch. Precisely the moment it happens: after years of driving petrol, someone fills a diesel Skoda Octavia for the first time. Throw in rain, a phone call or a back seat full of kids, and the hand repeats what it has always done.
Next time you fill up around Trench: avoiding petrol in a diesel
- Not every forecourt in the UK follows green for unleaded and black for diesel, even if most generally do. Read the pump's label; the colour is just a clue.
- The first fill in a new motor is the time to check your filler flap — inside it, or on the cap, plenty of cars state the fuel they take.
- Good intentions do less than a sticker or a fob in a bright colour on your diesel's key when a house has one of each. So mark it.
- Say it before you lift it. On the first fill in a new or hired car, say "diesel" out loud before you lift the nozzle off the pump. It sounds daft and it works.
- Whilst you're thinking about something else, this is an easy mistake to make — so put your phone away.
- Up to a point, a misfuel inhibitor helps: some diesels come with a filler designed to refuse a petrol nozzle, and aftermarket devices exist for the remainder. Treat it as a safety net, and keep reading the petrol pump.
- Less petrol means a weaker blend, and so stop as soon as you notice — though remembering that your next step is unchanged. It's still not to crank it.
Put petrol in a diesel around Trench already?
Short and simple, then, is the order of things. Do not switch the ignition on, and don't fire it up. Ask the attendants to help you push it clear of the petrol pump if you're still at the forecourt, whether that is Esso or somewhere else. Then ring 0333 366 0103 and tell us what got in, about how much, and whether it's run.
Say so if it was AdBlue rather than petrol: it's a separate problem, with its own page for Trench, since AdBlue brings corrosion and deposits rather than lost protection.
Trench petrol in a diesel tasks: why one costs more than another
Four separate tasks lie behind the four situations above — which is why there is no honest single quote. Mostly, the cost moves with which situation you are in. Next it is the share — how much petrol was put in against how much that tank takes — and after that where your car is and whether a van can reach it safely.
Three queries come first, before any quote, rather than after — what got in, how much, has it run — and this is the reason. A range becomes a straight figure once the replies are in.
About Trench
Trench is a suburban area in Shropshire, situated inland at an elevation of 91 metres, with Trench Lock and Wrockwardine Wood nearby. Trench is characterized by its predominantly semi-detached housing stock, reflecting the typical residential development of the West Midlands region. Trench is located approximately 16 miles from Wolverhampton and 129 miles from London, making it a commuter-friendly location. Trench has a population of around 4584 residents, according to recent estimates.
Trench and Shropshire: where our fuel drain cover runs
Trench Lock, Wrockwardine Wood and Hortonwood are among the locations around Trench that the same teams work, answering petrol in diesel jobs across Trench's TF postcode area. The car does not 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 Trench and still at the petrol pump?
Nothing beats it: that is where you now are. Keep it off. Ring.