Troedyrhiw: Petrol in a Diesel Car? How Worried to Be
Far less than you likely are, provided it hasn't been started. Petrol sitting in a diesel tank does nothing to your engine until something pulls it through the fuel system — the ignition priming the pump, your starter, or the drive itself. So the truthful answer to the first query anyone in Troedyrhiw asks, "have I ruined it?", is normally no. Petrol in Diesel is who to ring, with your motor kept off, so it stays that way. What petrol really does to a diesel, how to judge how far it's travelled, and how to keep it from happening a second time: that's the remainder of this page.
Inside the engine: what petrol in a diesel really does
Diesel has two tasks on its way through an engine. It lubricates to begin with, and only then does it burn. Designed to very fine tolerances, the injectors and the pump rely on your diesel flowing through them to keep their surfaces from wearing against one another.
The second job petrol doesn't do at all, and the first it does badly. A pump running on a petrol mix is wearing itself out, because petrol is runnier than diesel and strips out the protection your fuel system relies on. Petrol is also designed to resist igniting under compression — the reverse of what a diesel needs from its fuel — and that's where any rattling comes.
Seen together, they show the shape the issue takes. Not contact but movement is what does the damage. Petrol in the tank is a fuel fault. The beginning of a mechanical one is a pump that has been working on that petrol — and whatever a worn pump sheds moves on with your fuel to your injectors beyond it.
How bad is petrol in a diesel? Four scenarios our engineers see in Troedyrhiw
Filled but not once started — the best it gets. On a forecourt, and really only there, the petrol is still confined to the tank — since everywhere else the vehicle was driven to get to it. The task is draining and purging on the spot.
Ignition on, or started for a moment. Petrol has left that tank and reached the filter and the lines, since your system has been bled. Still normally easy: drain, flush, and the fuel filter sorted.
A few miles driven, and your pump has spent each of them running on weakened fuel. How hard the vehicle was driven matters as much as how far, and the work takes in that tank, your lines, the fuel filter and clean fuel through the entire system. The school run to the local primary school is one thing. Very different again: a trip to Newport, under 25 miles away, or any mileage on the M4, under 15 miles from Troedyrhiw, where your engine never stopped working hard.
It protested, and only then stopped: smoke, rattling, a throttle gone soft, an idle gone lumpy. The motor is telling you the fuel is no longer acting like diesel. Leave it wherever it has stopped: a lay-by, a quiet street, the verge on Yew Street. What goes first is still the drain and flush, and that deals with it, with long-term damage very unusual when a vehicle is pulled over soon.
Petrol in a diesel stories Troedyrhiw people hear
False: topping up to full with diesel makes it fine. It doesn't. A bigger tank of the same mixture is all it gives, since topping up removes nothing. That guidance presumes a diesel fuel system tolerates petrol by percentage. It does not.
Myth: "A newer diesel can cope with a bit of petrol." If anything, the reverse. At higher pressure, through more precise parts: that's how a current diesel moves its fuel, so the lubrication matters more, not less.
This is the one that fools motorists. Myth: "If it starts and drives, there is no harm done." Any petrol engine fed diesel generally won't run, so the motorist stops and the damage stops with them. Whilst your pump wears, a diesel fed petrol normally starts, idles and drives away as though nothing has happened. Being able to run isn't proof of being fine.
An outdated workaround for a different issue is behind this one. Myth: "Add some two-stroke oil and drive the car home." What petrol has diluted stays thinned, and the petrol stays inside that tank regardless.
Myth: "Drain your tank yourself and you're sorted." After the motor has run, some of that petrol is no longer in that tank: it is in your filter and the fuel lines, and it goes right back through your pump at your next start. And, a can of petrol drained by the kerbside is genuinely dangerous.
Why petrol in a diesel occurs so easily
It is rarely carelessness, and no one does it on purpose. A diesel nozzle mostly won't go into a petrol vehicle, yet the smaller petrol nozzle goes into the filler of a diesel almost without resistance — so forecourts make this one mistake straightforward, and just in one direction.
When routine and your car stop matching, it occurs. A new motor, a hire car or a courtesy car. A household with one petrol and one diesel on the driveway. The pumps in a different order on a well-known forecourt. Fuelling up in a rush on the way to Troed-Y-Rhiw, with a train to catch. Precisely the moment it happens: after years of driving petrol, someone fills a diesel Renault Clio for the first time. Add a back seat full of children, a phone call or rain, and habit takes over.
How to avoid petrol in a diesel on your next fill-up in Troedyrhiw
- The label is what matters, and so read the pump rather than the colour: in the UK unleaded handles are usually green and diesel black, yet not on each forecourt.
- 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 do less than a sticker or a fob in a bright colour on the diesel's key when a house has one of each. So label it.
- It seems silly and it does the trick: on the first fill in a new or hired car, say "diesel" aloud before you take the nozzle off the petrol pump.
- Mistakes like this are straightforward to make while your mind is on something else, so your phone goes away.
- Some diesels come with a filler built to reject a petrol nozzle, and devices you can add exist for motors without one. Such an inhibitor helps up to a point — as a backstop, not a reason to stop reading the petrol pump.
- As soon as you realise, stop: less petrol in the tank means a weaker blend. What to do next doesn't change, though — still do not fire it up.
Put petrol in a diesel around Troedyrhiw already?
Then, there is just a short order of things. Starting it is out, and so is switching on the ignition. Yet at the forecourt, at Applegreen or anywhere else? Ask the staff to help you push it clear of the pump. Call 0333 366 0103 next, with three answers — the fuel, the approximate quantity, and if it's run.
Say so if it was AdBlue rather than petrol: it is a different issue, with its own page for Troedyrhiw, because AdBlue brings corrosion and deposits instead of lost protection.
Why one petrol in a diesel task in Troedyrhiw costs more than another
There is no honest single price for this, since the four situations above are four different jobs. What shifts the cost is chiefly which of them you're in. Two things follow that: the petrol that went in as a share of what your tank takes, then the spot the vehicle is in and whether a van can get to it safely.
Three queries come first, before quoting, instead of after — what got in, how much, has it run — and this is the reason. Their replies are what change a range into one firm number.
About Troedyrhiw itself
Troedyrhiw is a village situated in the county of Merthyr Tydfil, alongside the River Taff in south Wales. Troedyrhiw has a mix of old and new housing, with many traditional terraced homes, and is located near the communities of Pentrebach, Abercanaid, and Aberfan. Troedyrhiw sits at an elevation of around 140 metres above sea level, with the city of Newport approximately 17 miles to the south. Troedyrhiw is a relatively small village, with a population of around 2077 people.
Troedyrhiw and Merthyr Tydfil: where our fuel drain cover runs
The teams answering petrol in diesel calls in Troedyrhiw, in the CF postcode area, also work the locations around it, Pentrebach, Abercanaid and Aberfan included. The car does not need to come to us: we drain at a forecourt, in a supermarket car park, in a lay-by or on your own driveway.
In Troedyrhiw and still at the petrol pump?
No position is better: that's where you now are. Phone, and keep it switched off.