How Worried Should You Be? Petrol in a Diesel Car in Mevagissey
Unstarted? Then less anxious than you probably feel. Petrol sitting in a diesel tank does nothing to the motor until something pulls it through the system — the ignition priming your pump, the starter, or the drive itself. So the fair answer to the first question everyone in Mevagissey asks, "have I wrecked it?", is usually no. To leave it that way, ring Petrol in Diesel and leave your engine alone. The remainder of this page covers what petrol actually 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
On its way through an engine, diesel does two jobs. Before it burns, it lubricates — then it burns. Extremely fine gaps go into your injectors and your high-pressure pump, and just your diesel flowing through stops their surfaces grinding together.
Poorly at the first, not at all at the second: that's petrol. A pump running on a petrol blend is wearing itself out, because petrol is thinner than diesel and strips out the protection the fuel system relies on. Petrol is also designed to resist igniting under compression — the opposite of what a diesel needs from its fuel — and that's where any knocking starts.
Seen together, they show the shape the issue has. Contact does not do the damage — movement does. Petrol in a tank is a fuel fault. A pump that has been running on that petrol is the start of a mechanical one, and whatever a worn pump sheds moves on with your fuel to your injectors downstream.
How bad is petrol in a diesel? Four scenarios our engineers see around Mevagissey
Fuelled up, never started. The best case there can be. At a forecourt, and really only there, that petrol is still limited to your tank — because everywhere else your car was driven to get to it. The job is emptying and purging on the spot.
Started for a second, or only your ignition on. With the system primed, the lines and filter already hold petrol that has come from your tank. Still generally straightforward: drain, flush, and your filter dealt with.
Driven a couple of miles. Now the pump has spent these miles labouring on weakened fuel. Tank, lines, filter, then clean fuel put through the entire system: that's the work, and the way the vehicle was driven matters as much as the miles. On the school run to Mevagissey Community Primary School, the miles is small. Very different a second time: a trip to Truro, under 15 miles away, or any distance on the M5, over 50 miles from Mevagissey, where the engine kept working hard.
Knocking, a lumpy idle, smoke, a throttle gone soft: driven until it complained. The engine is telling you your fuel is no longer acting like diesel. Leave it where it stops: a lay-by, a side street, the verge on Portmellon Road. The fuel drain and flush-through still go first, and they sort it out: when a vehicle is pulled over quickly, lasting damage is very uncommon.
Mevagissey people and that petrol in a diesel myths they hear
Myth: "Fill it the rest of the way with diesel and it will be fine." It will not. Nothing is removed by topping up — you're left with a bigger tank, still the same mixture. The idea behind that advice — that diesel fuel systems tolerate petrol by percentage — is wrong.
"Current diesels can handle a little petrol" — a myth, and closer to the reverse. At higher pressure, through finer parts: that is how a newer diesel handles its fuel, and so the protection counts more, not less.
This is the one that fools motorists. Myth: "If it starts and drives, there's no damage done." The driver of a petrol engine fed diesel normally has no choice but to stop, because it will not run, and the damage stops there. A diesel fed petrol generally starts, ticks over and drives away as though nothing has happened, whilst the pump wears. A running engine doesn't mean fine.
An outdated workaround for a different fault lies behind this one. Myth: "Add some two-stroke oil and drive it home." None of what petrol diluted is put back by it — and afterwards, the tank still contains the petrol.
Once the engine has run, part of that petrol is in the filter and the lines, not that tank — and your next start pulls it straight back through the pump. So the myth "drain your tank yourself and you are sorted" does not stand up. It is also genuinely hazardous to drain petrol into a can by the kerbside.
Why petrol in a diesel occurs at all
It is rarely carelessness, and nobody does it on purpose. A diesel nozzle mostly will not go into a petrol vehicle, but the slimmer petrol nozzle goes into the filler of a diesel almost without resistance — so forecourts make this one error simple, and only in that direction.
It takes place when habit and the vehicle stop matching. A motor that is new to you — a hire car, on loan as a courtesy car, or brand new. One petrol and one diesel on the drive of the same household. A forecourt you know, but with its pumps laid out differently. A train to catch, and a rushed fill on the way to St Austell. Years of petrol cars behind you, a diesel Renault Megane in front of you on the forecourt for its first tank — that's when. With rain, a call arriving, or children to deal with, the hand just does what it always has.
Preventing petrol in a diesel next time you fill up in Mevagissey
- Not every forecourt in the UK follows green for unleaded and black for diesel, though most usually do. Read the pump's label; the colour is just a hint.
- Check your filler flap. Plenty of motors state the fuel type inside the flap or on the cap. Look at it on your first fill in any motor you don't know.
- One of each in the home? Mark your key to your diesel — a bright fob, a sticker — since meaning to remember isn't enough.
- Before the nozzle comes off the petrol pump the first time you fill a hired or new car, say "diesel" aloud. Daft, yes, but it works.
- Thinking about something else is when this becomes an easy mistake to make, so put your phone away and keep your mind on the petrol pump.
- Add-on devices exist for vehicles without one, and some diesels are built with a filler that won't accept a petrol nozzle. Helpful — but a safety net only, never a reason to stop checking the label.
- Less petrol means a thinner mixture, and so stop the moment you realise — while remembering that your next step is unchanged. It is still not to start the car.
Put petrol in a diesel around Mevagissey already?
The order of things is short, then. Starting it is out, and so is switching on the ignition. If you're still on the forecourt — Texaco or anywhere else — ask the staff to help you push the car away from the pump. Then phone 0333 366 0103 and tell us what was put in, roughly how much, and whether it's run.
Say so if it was AdBlue rather than petrol: it is a separate problem, with its own page for Mevagissey, since AdBlue brings corrosion and deposits rather than lost protection.
Why one petrol in a diesel task in Mevagissey costs more than another
An honest single quote does not exist here: four scenarios, four separate jobs. Mostly, your cost shifts with which situation you're in. Where the vehicle is matters too, and whether a van can safely reach it, after the ratio of petrol to what your tank takes.
Three queries come first, before quoting, instead of after — what went in, how much, has it run — and this is the reason. The answers turn a range into a straight figure.
About Mevagissey
Mevagissey is a small coastal village in Cornwall, situated on the south coast at an elevation of around 4 metres. Mevagissey has a population of approximately 248 people and is characterised by predominantly detached housing. Mevagissey is located near other small settlements such as Portmellon and Trevarth Estate, and is within a short distance of the city of Truro. Mevagissey remains a quiet and secluded community, some 220 miles from London.
Fuel drain cover across Cornwall, Mevagissey included
Mevagissey rests in the PL postcode area, and the teams that answer petrol in diesel jobs there work the locations near it as well — Portmellon, Trevarth Estate and Trewollock among them. The car doesn't 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.
Still at the petrol pump around Mevagissey?
The best spot there is, then — that's where you are. Call, and keep it switched off.