Tetchill: Petrol in a Diesel Car? How Worried to Be
If it hasn't been started, worry far less than you probably are. Everyone in Tetchill begins with "have I wrecked it?", and the fair answer is usually no: petrol resting inside that tank of a diesel stays harmless till priming, cranking or driving draws it into the system. Petrol in Diesel is who to phone, with the motor left off, and so it stays that way. The rest of this page explains what petrol really does to a diesel, how to judge 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
Two jobs fall to diesel on its journey through a motor. Lubricating comes before burning; it does both. The high-pressure pump and the fuel injectors are made to very fine tolerances, and your diesel passing through them is what stops those surfaces from wearing down against each other.
Petrol does the first task badly and the second not at all. It's thinner than diesel and strips away the protection your fuel system rests on, and so a pump running on a petrol blend 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 make clear the shape the issue has. Not contact but movement is what does the damage. All a tank with petrol in it amounts to is a fuel fault. After your pump has been labouring on that petrol, a mechanical issue has started: whatever is shed by a pump that's grinding travels downstream to your injectors with your fuel.
Tetchill, petrol in a diesel: four cases, from mild to major
The best case there is: filled up, not once started. Being on a forecourt is what makes this the case: elsewhere, the vehicle has been driven there to begin with. With that petrol held in that tank alone, it's cleared and cleaned right where it stands, and nothing more is needed.
Ignition on, or started for a moment. With the system primed, the lines and filter now contain petrol that has come from your tank. Normally nothing more than clearing, cleaning and sorting the fuel filter, so still easy.
The pump has worked a couple of miles on weakened fuel — that is what driving it does. Distance is only half of it; how hard it was driven counts equally. Either way this work runs to your tank, the fuel lines, the fuel filter and fresh fuel through the entire system. Driving the children to Ellesmere Primary School is one kind of trip. Very different a second time: a trip to Wrexham, under 15 miles away, or some mileage on the M54, under 25 miles from Tetchill, where the motor kept working hard.
Clattering, an uneven idle, smoke, a throttle gone soft: driven till it complained. That is the motor telling you its fuel has stopped behaving like diesel. Whether it is the verge on Eaton Court, a lay-by or a side street, stop there and leave it. What goes first is still the drain and flush-through, and that sorts it out, with lasting damage very uncommon when a car is pulled over early.
Tetchill motorists and the petrol in a diesel myths they hear
"Top it up the rest of the way with diesel and it'll be fine" — a myth. It will not. Nothing is removed by topping up — you're left with a fuller tank, still the same mixture. That advice assumes a diesel fuel system tolerates petrol by percentage. It does not.
"Current diesels can handle a little petrol" — a myth, and closer to the opposite. Finer components and higher pressure are the way a current diesel runs its fuel, and that makes the lubrication matter more, not less.
"It starts, it drives, and so there is no harm" — the myth that trips up more people than any other. Feed diesel to a petrol engine and it usually won't run, and so the motorist stops — and the harm stops with them. While the pump wears, a diesel fed petrol usually starts, ticks over and drives away as if nothing has happened. Being able to run is not proof of being fine.
Not so: a two-stroke additive lets you to drive home. It was an old fix, meant for another problem. None of what petrol weakened gets put back by it — and afterwards, that tank still holds the petrol.
"Drain it yourself and you are sorted" — a myth, since after it's been running some petrol sits in the fuel filter and lines, ready to go right back through the pump at your next start. It's also truly risky to drain petrol into a can at the roadside.
Petrol in a diesel: how does it happen?
On purpose? Never. Through carelessness? Seldom, if ever. The petrol nozzle is the smaller of the two and slides into a diesel filler with almost no resistance; a diesel nozzle mostly will not go into a petrol car at all. The forecourt makes it easy, and the mistake runs one way.
It happens when routine and your car stop matching. A new vehicle, a hire car or a courtesy car. One petrol and one diesel on the drive of the same household. A familiar forecourt with the pumps in a different order. A rushed fill en route to Gobowen with a train to catch. Precisely the moment it happens: after years of driving petrol, a driver fills a diesel Renault Clio for the first time. With rain, a call arriving, or children to deal with, the hand just does what it always has.
Next time you fill up in Tetchill: preventing petrol in a diesel
- The label is what matters, and so check the petrol pump instead of the colour: in the UK unleaded handles are usually green and diesel black, but not on every forecourt.
- Check your filler flap. Many cars state the fuel inside the flap or on the cap. Look at it on the first fill in any motor you do not know.
- Label your key. In a household with one of each, a coloured fob or a sticker on the diesel's key does more than any amount of meaning to remember.
- Before the nozzle comes off the petrol pump the first time you fuel a hired or new car, say "diesel" aloud. Silly, yes, but it works.
- Mistakes like this are easy to make whilst your mind is on something else, and so the phone goes away.
- A misfuel inhibitor helps, up to a point. Some diesels come with a filler built to refuse a petrol nozzle, and add-on devices exist for cars without one. They are a safety net, not a reason to stop checking the petrol pump.
- Stop the moment you notice. Less petrol in that tank makes a thinner mixture. It doesn't change what to do next, which is still not to start it.
Already put petrol in a diesel around Tetchill?
Short and simple, then, is the order of things. Do not crank it, and do not turn the ignition on. Ask the staff to help you roll it away from the pump if you are still at the forecourt, whether that's Texaco or somewhere else. Then ring 0333 366 0103 and tell us what got in, about how much, and if it's run.
Corrosion and deposits are the trouble with AdBlue, where petrol means lost protection. So if it was AdBlue, say so — and read its own Tetchill page.
One petrol in a diesel task in Tetchill costs more than another. Why?
There is no fair single price for this, since the four situations above are four different tasks. Which of them you're in is mostly what shifts your cost. Two things follow that: the petrol that went in as a share of what the tank holds, then the spot your car is in and whether a technician can reach it safely.
What went in, how much, and if it's run — three queries our technicians ask before pricing, not after, for exactly that reason. A range becomes a straight figure when the replies are in.
About Tetchill and where it is
Tetchill is a small village in Shropshire, situated on the riverside at an elevation of 92 metres, with detached housing being the predominant type of accommodation. Tetchill lies near the villages of Lee, Newnes, and Hordley, and is approximately 11.6 miles from Wrexham. Tetchill has a population of around 544 people and is located in a rural area of the West Midlands region. Tetchill is also relatively distant from London, at a distance of 151.5 miles.
Across Shropshire and in Tetchill: fuel drain cover
Petrol in diesel call-outs around Tetchill — part of the SY postcode area — go to vans that also cover the spots around it, Lee, Newnes and Hordley included. The car does not need to move to us: our technicians drain at a forecourt, in a supermarket car park, in a lay-by or on your own driveway.
In Tetchill and still at the pump?
No position is better: that is where you are. Leave the car switched off, and ring.