Bryn Merllyn: Petrol in a Diesel Car? How Worried to Be
Provided it hasn't been started, worry far less than you probably are. Petrol sitting in a diesel tank does nothing to the motor until something draws it through the system — your ignition priming your pump, your starter, or driving on its own. So the fair answer to the first query everyone in Bryn Merllyn asks, "have I wrecked it?", is generally no. Keep it like that: leave your engine off then phone Petrol in Diesel. Below, you will find what petrol actually does inside a diesel, how far it might have got, and how to stop it happening to you again.
Inside the engine: what petrol in a diesel really does
Diesel does two jobs on its way through a motor. It lubricates to begin with, and only then does it burn. Built to very fine gaps, the fuel injectors and your pump rely on your diesel flowing through them to keep their surfaces from wearing against one another.
Petrol handles the first job badly and the second not at all. A pump running on a petrol mix is wearing itself out, since petrol is thinner than diesel and takes away the protection the fuel system depends on. Petrol is also made to resist igniting under compression — the reverse of what a diesel needs from its fuel — and that's where the rattling starts.
Put these together and the shape of the problem is plain. The harm is done by movement, not by contact. A tank with petrol in it is a fuel issue. After the pump has been running on that petrol, a mechanical issue has begun: anything shed by a pump that's wearing down is carried downstream to the fuel injectors with the fuel.
Bryn Merllyn, petrol in a diesel: four situations, from mild to serious
Filled up, and never started: no case is better. Only your tank has petrol in it, so the job is emptying the tank and rinsing the fuel system where the car sits. This situation can only really take place at a forecourt: anywhere else, the vehicle got there by being driven.
A brief spell of running, or just your ignition on. Your system has been primed, so petrol has left your tank and reached your filter and your lines. That is usually still a simple job — a drain, a flush, and your filter dealt with.
A few miles driven, and your pump has spent each of them working on thinned fuel. Mileage is only half of it; how hard it was driven counts equally. Either way this work runs to that tank, the fuel lines, the filter and fresh fuel through the entire system. Short trips, such as the school run to Parkgate Primary School, are one thing. Any miles on the M53, under 10 miles from Bryn Merllyn, means the engine has worked hard throughout, and a run to St Asaph, under 15 miles away, is a very different job too.
Driven on until it protested — rattling, smoke, an uneven idle, a dead throttle. The fuel is not behaving like diesel any more, and the motor is saying so. Leave it wherever it has stopped: a lay-by, a quiet street, the verge on Stryd Tegeingl. A car stopped soon very seldom has lasting damage, since the fuel drain and the flush, which still go first, deal with it.
Bryn Merllyn drivers and the petrol in a diesel myths they hear
Myth: topping up to full with diesel makes it fine. It does not. Nothing is removed by topping up — you're left with a fuller tank, still the same mix. A diesel fuel system does not tolerate petrol by percentage in the way that guidance assumes.
Myth: "A modern diesel can cope with a bit of petrol." If anything, the opposite. A newer diesel runs its fuel through more precise components at higher pressure, which makes the protection matter more, not less.
One myth that catches motorists off guard: if it starts and drives, it must be unharmed. Feed diesel to a petrol engine and it normally won't run, and so the motorist stops — and the harm stops with them. A diesel fed petrol generally starts, ticks over and drives away as though nothing has happened, while the pump grinds. Being able to run isn't proof of being fine.
An outdated fix for a distinct issue lies behind this one. Myth: "Add some two-stroke oil and drive it home." It doesn't put back what petrol has diluted, and the petrol is still inside that tank after that.
The next start draws petrol back round the pump from the lines and the filter, where some of it sits once the engine has run. That's why draining the tank yourself doesn't sort it — a myth. Besides, petrol emptied into a can by the road is genuinely dangerous.
How does petrol in a diesel take place?
It is seldom carelessness, and no one does it on purpose. The petrol nozzle is the slimmer of the two and slides into a diesel filler with almost no resistance; a diesel nozzle generally won't go into a petrol car at all. The forecourt makes it simple, and the mistake runs one way.
The moment routine stops matching the car is the moment it takes place. A new vehicle, a hire car or a courtesy car. One petrol and one diesel on the driveway of the same household. The pumps in a different order on a well-known forecourt. A hurried fill en route to Flint with a train to catch. A new-to-you diesel Volkswagen Golf, its first fuelling, and a motorist accustomed to petrol: exactly when it occurs. Throw in rain, a phone call or a back seat full of children, and the hand does what it has always done.
Next time you fill up in Bryn Merllyn: preventing petrol in a diesel
- Not every forecourt in the UK keeps to green for unleaded and black for diesel, even if most usually do. Check the petrol pump's label; the colour is just a clue.
- In a car you do not know, look inside the flap over your filler or at the cap before your first fill: many vehicles state the fuel type there.
- One of each in the home? Mark the key to your diesel — a coloured fob, a sticker — since meaning to remember isn't enough.
- "Diesel", out loud, before you pick up the nozzle — each time a new or hired car gets its first tank. It sounds silly. It works.
- Put your phone away. This is an easy mistake to make while you're thinking about something else.
- Up to a point, a misfuel inhibitor helps: some diesels come with a filler built to refuse a petrol nozzle, and add-on devices exist for the rest. Treat it as a backstop, then keep reading the pump.
- Less petrol makes a thinner mix, and so stop the moment you realise — though remembering that your next step is unchanged. It's still not to crank it.
Petrol already in a diesel around Bryn Merllyn? Begin here
The order of things is brief, then. Leave it unstarted, with the ignition off as well. Ask the attendants to help you push it clear of the pump if you're still at the forecourt, whether that's the nearest petrol station or somewhere else. Then call 0333 366 0103 and tell us what was put in, about how much, and whether it has run.
If it was AdBlue instead of petrol, say so. That's a different problem — corrosion and deposits rather than lost protection — and it has its own page for Bryn Merllyn.
One petrol in a diesel job around Bryn Merllyn costs more than another. Why?
Four separate tasks lie behind the four situations above — which is why there is no fair single price. The scenario itself does most of the work of moving your cost. Where the car is counts too, and whether a van can safely get to it, after the ratio of petrol to what the tank takes.
That is why we ask three queries before pricing instead of after: what was put in, how much, and if it has run. Those replies turn a range into a straight figure.
About Bryn Merllyn, briefly
Bryn Merllyn is a coastal suburban area in Flintshire, situated near the towns of Bagillt and St Asaph. Bryn Merllyn lies at a low elevation of around 8 metres, close to the shoreline. Bryn Merllyn has a mix of housing types, but semi-detached homes are particularly prevalent in the area. Bryn Merllyn is part of a larger network of communities that include Pentre-bach and Gadlys.
Bryn Merllyn and Flintshire: where our fuel drain cover reaches
Bagillt, Pentre-bach and Gadlys are among the places around Bryn Merllyn that the same teams work, answering petrol in diesel call-outs across Bryn Merllyn's CH postcode area. Our engineers drain where the vehicle is — your own driveway, a lay-by, a supermarket car park, a forecourt — so it does not have to come to us.
Still at the petrol pump around Bryn Merllyn?
In that case, you could not be in a better place. Switched off it stays; then ring.