How Worried Should You Be? Petrol in a Diesel Car in St Marychurch
Unstarted? Then less anxious than you probably feel. Until the ignition primes your pump, your starter cranks, or your car is driven, petrol in a diesel tank simply waits there and does nothing. Which makes the honest reply to that first St Marychurch query — "have I ruined it?" — usually no. Petrol in Diesel is who to phone, with the engine kept off, and so it remains that way. What petrol really does to a diesel, how to judge how far it's gone, and how to keep it from happening a second time: that's the rest of this page.
Petrol in a diesel: what does it do to the engine?
Passing through an engine, diesel does two things at once. Before it combusts, it protects — and then it combusts. The high-pressure fuel pump and the fuel injectors are designed to extremely fine gaps, and your diesel passing through them is what keeps those surfaces from wearing against one another.
The second job petrol doesn't do at all, and the first it does badly. The knocking comes from petrol being designed not to ignite when compressed, which is precisely the opposite 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 running on that blend is wearing itself.
Seen together, they make clear what shape the trouble takes. Not contact but movement is what causes the damage. Petrol in a tank is a fuel problem. Whatever a worn pump sheds goes on, carried by your fuel, into your injectors downstream, which is why a pump that has been working on that petrol is where a mechanical fault starts.
How bad is petrol in a diesel? Four scenarios our engineers see in St Marychurch
Filled up, never started. The best case there can be. Only the tank has petrol in it, so the task is clearing your tank and rinsing the fuel system where your car sits. This situation can only really occur at a forecourt: anywhere else, the car got there by being driven.
Ignition on, or started for a second. The system has been bled, so petrol has left that tank and got to your filter and your lines. Drain, flush, deal with the fuel filter: still usually simple.
A few miles driven, and the pump has spent each of them working on weakened fuel. Mileage is only half of that; how hard it was driven matters equally. Either way this work runs to that tank, the fuel lines, your filter and fresh fuel through the entire system. On the school run to Homelands Primary School, the miles is small. Driving as far as Exeter, under 25 miles away, makes a very different job — as does any distance on the M5, under 15 miles from St Marychurch, with your engine labouring hard the whole time.
It complained, and only then stopped: smoke, knocking, a throttle gone soft, an idle gone ragged. The fuel isn't acting like diesel any more, and your motor is telling you. Stop wherever you are — the verge on Manor Road, a lay-by, a side street — and leave it there. Lasting damage is very unusual when a vehicle is stopped soon, and the fuel drain and flush that still go first take care of it.
Petrol in a diesel myths St Marychurch drivers hear
Myth: "Fill it the rest of the way with diesel and it'll be fine." It will not. Topping up takes out nothing; it gives you a bigger tank of the same mixture. The assumption behind that guidance — that diesel fuel systems accept petrol by percentage — is wrong.
If anything, the opposite holds. Myth: "A modern diesel can cope with a bit of petrol." At higher pressure, through smaller parts: that is how a modern diesel handles its fuel, so the lubrication matters for more, not less.
"It starts, it drives, and so no harm done" — the myth that catches more drivers than any other. Feed diesel to a petrol engine and it generally will not run, and so the motorist stops — and the harm stops with them. While the pump wears, a diesel fed petrol usually starts, idles and drives away as if nothing has happened. A running engine doesn't mean fine.
"A drop of two-stroke oil and drive it home" — a myth, taken from a fix from years ago, for a different problem. It does not put back what petrol has thinned, and that petrol is still in your tank later on.
The next start sends petrol back round the pump out of the lines and your filter, where some of that sits after the motor has run. That's why a DIY tank drain does not leave you sorted — a myth. Besides, petrol cleared into a can by the road is genuinely hazardous.
Petrol in a diesel: how does it happen?
Nobody does it on purpose, and it's rarely carelessness. The forecourt makes it easy: the petrol nozzle is the smaller of the two, and it slides into a diesel filler with almost no resistance, while a diesel nozzle mostly won't go into a petrol motor at all. So the mistake runs one way.
It occurs when routine and the vehicle stop matching. Hire cars, courtesy cars, and cars that are new to you. A household with one petrol and one diesel on the drive. A forecourt you know, only with its pumps laid out differently. A train to catch, and a rushed fill en route to Torre. Exactly the moment it takes place: after years of driving petrol, a driver fills a diesel Renault Megane for the first time. 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 St Marychurch: avoiding petrol in a diesel
- Green for unleaded and black for diesel is usual in the UK — yet not on every forecourt. Go by the label on the petrol pump, not the colour.
- Inspect the filler flap. Many vehicles state the fuel inside the flap or on the cap. Look at it on the first fill in a motor you do not know.
- Mark the key. In a household with one of each, a coloured fob or a sticker on your diesel's key does more than any amount of intending to remember.
- It sounds silly and it does the trick: on your first fill in a new or hired car, say "diesel" out loud before you lift the nozzle off the petrol pump.
- Whilst you're thinking about something else, this is an easy mistake to make — so tuck the phone away.
- A misfuel inhibitor helps, up to a point. Some diesels have a filler designed to refuse a petrol nozzle, and add-on devices are available for cars without one. They are a safety net, not a reason to stop reading the pump.
- Stop the moment you notice. Less petrol inside that tank means a thinner blend. It doesn't change what to do next, which is still not to crank it.
Already put petrol in a diesel in St Marychurch?
The order of things is short, then. Never fire it up, and do not switch your ignition on. Still on the forecourt, at Esso or anywhere else? Ask the staff to help you push the vehicle clear of the pump. Next, 0333 366 0103. We will ask what went in, roughly how much, and if it has been run.
If it was AdBlue rather than petrol, say so. That is a different problem — corrosion and deposits rather than lost protection — and it has its own page for St Marychurch.
What makes one St Marychurch petrol in a diesel task cost more than the next
There is no honest single quote for this, since the four scenarios above are four separate tasks. What shifts your cost is chiefly which of them you're in. Two things come after that: the petrol that went in as a share of what the tank holds, then the spot the car is in and whether our van can reach it safely.
Three questions come first, before any quote, instead of after — what went in, how much, has it run — and that is the reason. A range turns into a straight figure once the replies are in.
About St Marychurch, for a moment
St Marychurch is a suburban area on the coast of Devon, situated near the towns of Torquay and Paignton. St Marychurch sits at an elevation of around 90 metres, overlooking the English Channel. St Marychurch is characterised by its predominantly terraced housing and is located near other suburban areas such as Plainmoor and Babbacombe.
Across Devon and around St Marychurch: fuel drain cover
St Marychurch waits in the TQ postcode area, and the teams that answer petrol in diesel jobs there work the locations near it as well — Plainmoor, Babbacombe and Ellacombe among them. The car doesn't need to come to us: our engineers drain at a forecourt, in a supermarket car park, in a lay-by or on your own driveway.
At the pump in St Marychurch, right now?
No position is better: that is where you now are. Ring, and keep it switched off.