Should You Worry? Petrol in a Diesel Car in Leigham
Unstarted? Then less worried than you probably are. Everyone in Leigham starts with "have I wrecked it?", and the fair answer is usually no: petrol left inside your tank of any diesel stays harmless until priming, cranking or driving pulls it into your fuel system. Petrol in Diesel is who to call, with your motor left off, and so it stays that way. What petrol actually does to a diesel, how to judge how far it's gone, and how to keep it from happening a second time: that is the remainder of this page.
What petrol in a diesel does to the engine
Passing through an engine, diesel is doing two jobs at the same time. Before it burns, it lubricates — then it combusts. What keeps the surfaces inside the high-pressure fuel pump and your injectors from wearing down against each other is the diesel flowing through them — they are designed to extremely fine gaps.
Petrol does the first task poorly and the second not at all. Being less viscous than diesel, petrol strips away the protection a fuel system needs, so a pump on that mixture wearing itself. It is equally made to resist igniting under compression — the reverse of what a diesel needs — which is where you get the rattling.
Combined, those leave the shape of the issue plain. Not contact but movement is what does the harm. Where that petrol is only inside that tank, it is a fault of fuel, nothing more. A pump that has been labouring on that petrol is the beginning of a mechanical one, and whatever a worn pump sheds moves on with your fuel to your injectors downstream.
Four situations our technicians see in Leigham: how serious is petrol in a diesel?
The best case there is: filled up, never started. Being at a forecourt is what makes this the case: elsewhere, the car has been driven there to begin with. With the petrol kept inside your tank alone, it's drained and rinsed on the spot, and nothing more is needed.
The ignition switched on, or a short start. Once primed, the fuel system has pulled petrol out of that tank up to the filter and your lines. Drain, flush, deal with your filter: still usually straightforward.
Driven a couple of miles. Now your pump has spent those miles labouring on thinned fuel. Tank, lines, filter, then clean fuel put through the entire system: that is this work, and the way your car was driven matters as much as the miles. On the school run to Leigham Primary School, the mileage is small. Very different a second time: a run to Plymouth, under 5 miles away, or any miles on the M5, under 50 miles from Leigham, where the engine kept running hard.
Clattering, a ragged idle, smoke, a throttle gone soft: driven until it complained. The fuel isn't acting like diesel any more, and the motor is telling you. Pull up where you are — on the verge on Bampton Road, at the kerb, down a side road — and don't move it. A car stopped soon very rarely has lasting damage, because the drain and the flush, which still come first, sort it out.
What Leigham motorists get told about petrol in a diesel — and the myths in it
False: topping up to full with diesel makes it fine. It does not. Nothing is removed by topping up — you are left with a fuller tank, still the same mix. That guidance assumes a diesel fuel system tolerates petrol by percentage. It does not.
"Newer diesels can handle a little petrol" — a myth, and closer to the reverse. Smaller components and higher pressure are the way a modern diesel runs its fuel, and that makes the protection count more, not less.
Myth: "If it starts and drives, there is no damage done." This is the one that catches drivers. Any petrol motor fed diesel generally will not run, so the motorist stops and the damage stops with them. Nothing looks to have happened when a diesel fed petrol fires up, ticks over and drives away, as it usually does; meanwhile the pump grinds. Being able to run is not the same as being fine.
Not so: a two-stroke additive lets you to drive home. It was an old workaround, supposed for another problem. None of what petrol diluted is put back by it — and later, the tank still contains the petrol.
Myth: "Drain the tank yourself and you are sorted." Once the engine has run, some of that petrol is no longer inside that tank: it's in the fuel filter and the lines, and it goes right back through your pump at your next start. It is also genuinely hazardous to drain petrol into a can by the roadside.
Why petrol in a diesel occurs so easily
A careless moment is rarely the cause, and nobody means to do it. One way only, because of the nozzles: the slimmer petrol one slides inside a diesel filler with almost no resistance, while the diesel one mostly won't fit a petrol car. That's how the forecourt makes it easy.
The moment routine stops matching the vehicle is the moment it happens. Courtesy car, hire car, or a motor that is new. Two vehicles on one drive, one petrol, one diesel. Your usual forecourt, its pumps now in a different order. A train to catch, and a hurried fill on the way to Plymouth. The first fill-up in a diesel Volkswagen Passat after years of driving petrol is precisely the moment it occurs. With rain, a call arriving, or a car full of children to deal with, the hand simply does what it always has.
Next time you fill up around Leigham: 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 only a hint.
- The first fill in an unfamiliar car is the time to check the filler flap — inside it, or on the cap, plenty of vehicles state which fuel to use.
- A coloured fob or a sticker on your diesel's key achieves more than any amount of meaning to remember, in a household with one of each.
- "Diesel", out loud, before you pick up the nozzle — every time a new or hired car needs its first tank. It sounds silly. It does the trick.
- Thinking about something else is when this becomes an easy mistake to make, and so put the phone away and keep your mind on the pump.
- A misfuel inhibitor helps, up to a point. Some diesels have a filler built to block a petrol nozzle, and add-on devices exist for cars without one. They are a backstop, not a reason to stop checking the petrol pump.
- As soon as you notice, stop: less petrol inside the tank makes a weaker mix. What to do next does not change, though — still do not start it.
Petrol already in a diesel in Leigham? Start here
Then the order of things is brief. Starting it is out, and so is turning on your ignition. If you are still at the forecourt — Esso or anywhere else — ask the staff to help you push the vehicle away from the pump. Next, 0333 366 0103. We'll ask what was put in, roughly how much, and if it has been run.
If it was AdBlue and not petrol, say so. That is a separate problem — corrosion and deposits rather than lost protection — and it has its own page for Leigham.
Why one petrol in a diesel task in Leigham costs more than another
A fair single price doesn't exist here: four situations, four separate jobs. What shifts the cost is chiefly which of them you're in. The proportion matters next, meaning how much of that tank is petrol, and then the position of the vehicle and whether getting to it is safe for our van.
Before any quote, not after, we ask three questions: your fuel that was put in, the volume, and whether it has run. That's why. With those replies, you get a straight figure rather than a range.
About Leigham itself
Leigham is a suburban area located on the outskirts of Plymouth in Devon, sitting at an elevation of 63 metres above sea level. Leigham is situated near the coast, with nearby places including Longbridge, Eggbuckland, and Mainstone. Leigham has a population of approximately 3349 residents, with a predominance of terraced housing. Leigham is close to the city of Plymouth, being only 3.1 miles away.
Leigham and Devon: where our fuel drain cover reaches
Leigham sits in the PL postcode area, and our teams that answer petrol in diesel calls there work the places around it as well — Longbridge, Eggbuckland and Mainstone among them. The vehicle does not need to move to us: our engineers drain on a forecourt, in a supermarket car park, in a lay-by or on your own drive.
At the petrol pump in Leigham, right now?
The best place there is, then — that's where you are. Keep it off. Phone.