Tewin: Petrol in a Diesel Car? How Worried to Be
Unstarted? Then less anxious than you probably feel. "Have I ruined it?" is the first question anyone around Tewin asks, and the truthful answer is normally no, because petrol resting in a diesel tank hurts nothing till it is dragged through the fuel system — by ignition priming, by your starter, or by driving. Petrol in Diesel is who to ring, with your engine kept off, and so it stays that way. Below, you will find what petrol really does inside a diesel, how far it may have gone, and how to stop it happening to you again.
Petrol in a diesel: what does it do to the engine?
Two jobs fall to diesel on its journey round a motor. It ignites, and before it ignites it lubricates. What stops the surfaces inside your high-pressure pump and your injectors from grinding against each other is the diesel passing through them — they are made to very fine clearances.
Of those two tasks, petrol manages the first badly and the second not at all. The knocking comes from petrol being designed not to ignite when compressed, which is precisely the reverse of what a diesel needs. On top of that it is thinner than diesel, it strips away the protection your system depends on, and any pump working on that blend is wearing itself.
Together, those leave the shape of the problem plain. It is movement that does the damage, not contact. A tank with petrol in it is a fuel issue. After the pump has been labouring on that petrol, a mechanical fault has started: whatever is shed by a pump that is wearing is carried onward to the injectors with your fuel.
Tewin, petrol in a diesel: four cases, from mild to significant
The best case there can be: filled up, not once started. Only that tank has petrol in it, and so the task is emptying your tank and flushing the system where the vehicle sits. This scenario can only truly happen on a forecourt: anywhere else, the vehicle got there by being driven.
Started for a moment, or only your ignition on. Once primed, your system has pulled petrol from that tank as far as the filter and the lines. Usually nothing more than draining, cleaning and sorting the fuel filter, so still simple.
Those few miles on the road meant the pump running on fuel thinned by petrol throughout. The work is that tank, the lines, your filter and fresh fuel through the whole system, and how hard the car was driven matters as much as how far. The school run to Tewin Cowper Church of England Voluntary Aided Primary School is one matter. Very different a second time: a trip to St Albans, under 10 miles away, or any mileage on the A1(M), under 3 miles from Tewin, where your engine never stopped working hard.
Rattling, an uneven idle, smoke, a throttle gone soft: driven till it complained. What you are hearing is your engine reporting fuel that no longer behaves like diesel. Pull up on the spot — on the verge on Upper Green Road, at the kerb, down a side road — and do not move it. The fuel drain and flush-through still come first, and they deal with it: when a car is stopped early, long-term damage is very rare.
Petrol in a diesel stories Tewin drivers hear
It will not be fine. The myth: "Fill it the rest of the way with diesel and it'll be." A fuller tank of the same mixture is all you get, since topping up takes out nothing. The assumption behind that advice — that diesel fuel systems accept petrol by percentage — is wrong.
"Modern diesels can handle a little petrol" — a myth, and closer to the opposite. Protection matters more on newer diesels, not less, since their fuel runs through more precise parts at higher pressure.
"It starts, it drives, and so no harm done" — the myth that catches most motorists than any other. The driver of a petrol engine fed diesel usually has no choice but to stop, because it will not run, and the harm stops with them. Whilst the pump wears, a diesel fed petrol usually starts, ticks over and drives away as though nothing has happened. A running engine does not mean fine.
Not so: a two-stroke additive lets you to drive home. It was an old workaround, supposed for another fault. The petrol is still in your tank afterwards, and whatever it has weakened isn't put back.
Myth: "Drain the tank yourself and you're sorted." After the motor has run, some of that petrol is no longer inside that tank: it's in your filter and the lines, and it goes right back through your pump at your next start. Clearing petrol into a can at the kerbside is also genuinely risky.
How it happens: petrol in a diesel
On purpose? Never. Through carelessness? Seldom, if ever. A diesel nozzle mostly will not go into a petrol vehicle, but the narrower petrol nozzle goes into the filler of a diesel nearly without resistance — so forecourts make this one mistake straightforward, and just in that direction.
Routine and your car getting out of step is how it happens. Courtesy car, hire car, or a motor that is new. Households running one of each, petrol and diesel. A well-known forecourt with the pumps in a different order. A hurried fill en route to Welwyn North with a train to catch. Years of petrol vehicles behind you, a diesel Volkswagen Golf in front of you at the forecourt for its first tank — that is when. The hand does what it has always done when you add rain, a phone call or a back seat full of children.
Next time you fill up in Tewin: avoiding petrol in a diesel
- A green handle for unleaded and black for diesel is normal in the UK — yet not on each forecourt. Go by the label on the petrol pump, not the colour.
- Many cars state the fuel type inside your filler flap or on the cap, so check it on your first fill in any car you do not know.
- A coloured fob or a sticker on the diesel's key does more than any amount of intending to remember, in a household with one of each.
- It seems silly and it does the trick: on the first fill in a new or hired car, say "diesel" out loud before you lift the nozzle off the petrol pump.
- Mistakes like this are straightforward to make while 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 are available for vehicles without one. They are a safety net, not a reason to stop checking the petrol pump.
- Spotting it mid-fill? Stop at once. A thinner blend results from less petrol inside your tank, yet your next step remains the same: do not fire it up.
Put petrol in a diesel in Tewin already?
In that case, there is just a short order of things. Starting it is out, and so is turning on the ignition. If you're still on the forecourt — Morrisons or anywhere else — ask the staff to help you push the car clear of the pump. What went in, about how much, and whether it's run: tell us those when you call 0333 366 0103.
Say so if it was AdBlue rather than petrol: it's a different issue, with its own page for Tewin, because AdBlue brings corrosion and deposits instead of lost lubrication.
What makes one Tewin petrol in a diesel task cost more than the next
There's no fair single price for this, because the four situations above are four different tasks. What moves the cost is chiefly which of them you're in. Where your car is counts too, and whether our van can safely get to it, after the proportion of petrol to what your tank holds.
That is why our engineers ask three queries before quoting instead of after: what went in, how much, and if it has run. A range turns into a straight figure when the replies are in.
About Tewin itself
Tewin is a small village in Hertfordshire, situated approximately 21 miles north of London and 9 miles southeast of St Albans. Tewin sits in a rural area at an elevation of around 82 metres, surrounded by woodland and open countryside, including Tewin Wood. Tewin has a population of around 615 people, living in predominantly detached houses, with nearby villages including Burnham Green and Harmer Green.
Fuel drain cover across Hertfordshire, Tewin included
Petrol in diesel calls in Tewin — part of the AL postcode area — go to teams that likewise cover the places round it, Tewin Wood, Burnham Green and Harmer Green included. We drain wherever the vehicle is — your own drive, a lay-by, a supermarket car park, a forecourt — so it does not have to come to us.
Tewin: still at the pump?
The best spot there is, then — that's where you are. Keep it off. Ring.