Should You Worry? Petrol in a Diesel Car in Tetsworth
Far less than you likely are, if it has not been started. Until the ignition primes your pump, the starter cranks, or the car is driven, petrol in a diesel tank just rests there and does nothing. Which makes the truthful reply to that first Tetsworth question — "have I ruined it?" — usually no. To keep the car that way, ring Petrol in Diesel then leave your motor switched off. Read on for three things: the effect petrol has inside a diesel engine, the signs of how far it has got, and the way to make sure you don't do it again.
What petrol in a diesel does to the motor
On its way through an engine, diesel has two tasks. Before it combusts, it protects — then it combusts. The high-pressure fuel pump and the fuel injectors are made to extremely fine tolerances, and the diesel passing through them is what keeps those surfaces from grinding against one another.
Of these two jobs, petrol manages the first poorly and the second never. Being less viscous than diesel, petrol strips away the protection a fuel system needs, leaving a pump running on that mixture to wear itself. It's also made to resist igniting under compression — the opposite of what a diesel needs — which is where you hear the knocking.
Combined, those make the shape of the problem plain. The damage is done by movement, not by contact. Where that petrol is only inside your tank, it is a fault of fuel, nothing more. Once the pump has been labouring on that petrol, a mechanical problem has started: anything shed by a pump that's wearing down travels downstream to the fuel injectors with the fuel.
Four scenarios our engineers see around Tetsworth: how serious is petrol in a diesel?
Fuelled, and never started: nothing beats it. At a forecourt, and really only there, that petrol is still confined to the tank — since everywhere else the vehicle was driven to reach it. The job is emptying and rinsing on the spot.
Started for a moment, or just the ignition on. The fuel system has been bled, so petrol has left that tank and got to the fuel filter and the fuel lines. Drain, flush, deal with the filter: still usually straightforward.
Driven a couple of miles. Now the pump has spent those miles labouring on weakened fuel. How hard the car was driven counts as much as how far, and this work covers that tank, the lines, your filter and fresh fuel through the entire system. Short trips, such as the school run to Tetsworth Primary School, are one thing. Very different again: a run to Oxford, under 15 miles away, or any mileage on the M40, under a mile from Tetsworth, where the engine never stopped working hard.
Driven till it protested. Knocking, a ragged idle, smoke, a throttle that has gone soft. What you are hearing is your engine reporting fuel that no longer runs like diesel. Whether it is the verge on Victoria Gardens, a lay-by or a side road, stop there and leave it. The drain and flush-through still go first, and they deal with it: if a car is pulled over early, permanent damage is very unusual.
Tetsworth motorists and the petrol in a diesel stories they hear
"Top it up the rest of the way with diesel and it'll be fine" — a myth. It will not. A bigger tank of the same mixture is all you get, since topping up takes out nothing. Percentage is not how a diesel fuel system tolerates petrol, however much that guidance supposes.
If anything, the reverse holds. Myth: "A newer diesel can cope with a bit of petrol." A modern diesel runs its fuel through smaller components at higher pressure, which makes the lubrication count more, not less.
The myth that catches motorists out: if it starts and drives, it must be unharmed. Any petrol engine fed diesel normally will not run, so the motorist stops and the harm stops with them. Nothing seems to have happened when a diesel fed petrol fires up, ticks over and drives away, which it usually will; meanwhile the pump wears. Being able to run isn't the same as being fine.
An outdated fix for a separate fault lies behind this one. Myth: "Add some two-stroke oil and drive it home." What petrol has weakened remains weakened, and the petrol stays in that tank regardless.
Myth: "Drain that tank yourself and you're sorted." Once your engine has been run, some of that petrol is no longer in the tank: it's in the filter and your lines, and it goes straight back through the pump on the next start. And, a can of petrol drained by the roadside is truly hazardous.
How does petrol in a diesel occur?
Carelessness is seldom the cause, and no one means to do it. The forecourt makes it easy: the petrol nozzle is the slimmer of the two, and it slides into a diesel filler with almost no resistance, whilst a diesel nozzle generally will not go into a petrol car at all. So the mistake runs one way.
When routine and the vehicle stop matching, it happens. Hire cars, courtesy cars, and cars that are new to you. Households running one of each, petrol and diesel. Your usual forecourt, its pumps now in a different order. A hurried fill en route to Haddenham & Thame Parkway with a train to catch. The first fill-up in a diesel Volkswagen Golf after years of driving petrol is exactly the moment it occurs. Throw in a back seat full of children, a phone call or rain, and habit takes over.
Tetsworth motorists: how to avoid petrol in a diesel next time
- Not every forecourt in the UK keeps to green for unleaded and black for diesel, though most usually 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 your filler flap — on it, or on the cap, plenty of motors state the fuel to use.
- A coloured fob or a sticker on the diesel's key achieves more than any amount of meaning to remember, in a household with one of each.
- Before the nozzle leaves the pump the first time you fill a hired or new vehicle, say "diesel" out loud. Silly, perhaps, but it does the trick.
- Whilst you are thinking about something else, this is an easy mistake to make — so tuck your phone away.
- A misfuel inhibitor helps, up to a point. Some diesels have a filler built to block a petrol nozzle, and add-on devices are available for motors without one. They are a safety net, not a reason to stop checking the pump.
- The moment you realise, stop: less petrol in your tank makes a weaker mix. What to do next does not change, though — still do not crank it.
Put petrol in a diesel in Tetsworth already?
In that case, there's only a short order of things. Leave it unstarted, with your ignition off too. If you're still at the forecourt — Murco or anywhere else — ask the staff to help you roll the car clear of the pump. Next, 0333 366 0103. We will ask what went in, about how much, and if it's been run.
Say so if it was AdBlue instead of petrol: it is a different issue, with its own page for Tetsworth, since AdBlue brings corrosion and deposits rather than lost lubrication.
Why one petrol in a diesel job in Tetsworth costs more than another
The four scenarios above are four separate tasks, so no single price for this would be fair. Which of them you are in is chiefly what shifts the cost. The proportion counts next, meaning how much of your tank is petrol, followed by the position of your car and whether reaching it is safe for a van.
Three questions come first, before quoting, rather than after — what went in, how much, has it run — and that is the reason. The replies turn a range into a straight figure.
About Tetsworth and its setting
Tetsworth is a small village in Oxfordshire, situated in the inland countryside of the South East region, with an elevation of around 91 metres. Tetsworth lies approximately 11 miles from Oxford and 40 miles from London, placing it within commuting distance of both cities. Tetsworth is characterised by its predominantly detached housing stock and is surrounded by nearby villages such as Adwell, Stoke Talmage, and Postcombe.
Fuel drain cover across Oxfordshire, Tetsworth included
Tetsworth sits in the OX postcode area, and our teams that answer petrol in diesel jobs there work the spots near it as well — Adwell, Stoke Talmage and Postcombe among them. A forecourt, a supermarket car park, a lay-by or your own driveway are all spots our engineers work, and your car does not need to move to us.
Still at the petrol pump in Tetsworth?
Then you are in the best position there is. Turned off it stays; then ring.