North End: Petrol in a Diesel Car? How Worried to Be
Not started? Then less worried than you probably feel. Until your ignition primes the pump, your starter cranks, or your vehicle is driven, petrol in a diesel tank simply sits there and does no harm. Which makes the honest reply to that first North End question — "have I wrecked it?" — normally no. Leave your motor off then call Petrol in Diesel — that keeps it like that. The remainder of this page sets out what petrol really does to a diesel, how to judge how far it has got, and how to make sure it does not happen to you a second time.
Inside the engine: what petrol in a diesel really does
Diesel has two tasks on its way through an engine. Before it burns, it lubricates — then it ignites. Made to extremely fine clearances, your injectors and the pump depend on the diesel moving through them to keep their surfaces from wearing against one another.
Petrol does the first task badly and the second not at all. It is thinner than diesel and removes the lubrication your fuel system hinges on, and so a pump running on a petrol blend is a pump wearing itself. And petrol is designed to resist igniting under compression, which is the reverse of what a diesel needs from its fuel. That's where the knocking comes from.
The shape of the issue is clear once you put those together. It's circulation that does the damage, not contact. All a tank with petrol in it amounts to is a fuel problem. 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 the fuel to your injectors further on.
Four scenarios our engineers see around North End: how serious is petrol in a diesel?
Filled up, not once started. The best case there can be. Only that tank has petrol in it, so the job is emptying your tank and flushing the system where your car stands. This scenario can only really occur at a forecourt: anywhere else, your car got there by being driven.
A moment's running, or just your ignition on. Petrol has left the tank and reached the fuel filter and your lines, since your system has been bled. That's usually still an easy task — a drain, a flush, and the fuel filter seen to.
Driven a couple of miles. Now the pump has spent these miles working on diluted fuel. How hard the vehicle was driven matters as much as how far, and the work covers that tank, the fuel lines, your filter and clean fuel through the whole circuit. A school run to Peareswood Primary School is one matter. Getting as far as London, under 15 miles away, makes a very different job — as does any mileage on the M25, under 5 miles from North End, with your engine labouring hard all the way.
Driven till it protested. Rattling, a lumpy idle, smoke, a throttle that has gone soft. What you are hearing is your motor reporting fuel that no longer runs like diesel. Pull up wherever you are — the verge on Bridge Road, a lay-by, a side street — and leave the car where it is. Permanent damage is very unusual when a vehicle is pulled over quickly, and the fuel drain and flush-through that still go first sort it out.
Myths North End drivers hear about petrol in a diesel
It will not be fine. The myth: "Fill it the rest of the way with diesel and it will be." Topping up takes out nothing; it gives you a fuller tank of the same mixture. Percentage isn't how a diesel fuel system copes with petrol, however much that guidance supposes.
If anything, the reverse holds. Myth: "A modern diesel can cope with a bit of petrol." A newer diesel sends its fuel through smaller parts at higher pressure, which makes the lubrication matter more, not less.
"It starts, it drives, and so no harm done" — the myth that trips up most motorists than any other. Diesel in a petrol motor normally means a motor that will not run: the driver stops, and so does the damage. A diesel fed petrol normally starts, ticks over and drives away as though nothing has happened, whilst the pump grinds. Being able to run is not the same as being fine.
Myth: "Add some two-stroke oil and drive it home." It is an old fix for a different fault. What petrol has diluted remains thinned, and that petrol remains inside your tank anyway.
Myth: "Drain that tank yourself and you are sorted." Once your engine has been run, some of that petrol is no longer in the tank: it's in your filter and the lines, and it goes right back through your pump at the next start. And, a can of petrol filled by the roadside is genuinely hazardous.
Why petrol in a diesel occurs so easily
It's rarely carelessness, and no one does it on purpose. A diesel nozzle generally will not go into a petrol car, yet the narrower petrol nozzle goes into the filler of a diesel almost without resistance — so forecourts make this one error simple, and just in that direction.
When habit and the car stop matching, it takes place. Any motor that is new to you — a hire car, on loan as a courtesy car, or just bought. One petrol and one diesel on the driveway of the same household. Your normal forecourt, its pumps suddenly in a different order. A hurried fill en route to Slade Green with a train to catch. Years of petrol motors behind you, a diesel Renault Megane in front of you at the forecourt for its first tank — that's when. The hand repeats what it has always done when you add rain, a phone call or a back seat full of kids.
How to avoid petrol in a diesel at your next fill-up around North End
- The label is what counts, so check the petrol pump rather than the colour: in the UK unleaded handles are normally green and diesel black, but not on every forecourt.
- Check the filler flap. Plenty of cars state the fuel type inside the flap or on the cap. Look at it on the first fill in a car you don't know.
- A coloured fob or a sticker on the diesel's key achieves more than any amount of meaning to remember, for a house with one of each.
- Say it before you lift it. On your first fill in a new or hired car, say "diesel" aloud before you lift the nozzle off the petrol pump. It seems silly and 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.
- Add-on devices exist for cars without one, and some diesels come with a filler that will not accept a petrol nozzle. Helpful — but a safety net at best, never a reason to stop checking the label.
- Noticing it mid-fill? Stop at once. A weaker mix results from less petrol in the tank, yet your next stage stays the same: do not crank it.
North End: already put petrol in a diesel?
Short and simple, then, is the order of things. Do not switch the ignition on, and do not crank it. Yet at the forecourt, at Shell or anywhere else? Ask the staff to help you push the vehicle away from the pump. What was put in, roughly how much, and whether it has run: tell us that when you ring 0333 366 0103.
AdBlue, not petrol? Then say so. Corrosion and deposits, not lost protection, make it a separate fault — North End has a page just for it.
Why one petrol in a diesel task in North End costs more than another
The four situations above are four separate tasks, so no single price for this would be honest. Chiefly, your cost shifts with which one you are in. The share counts next, meaning how much of your tank is petrol, followed by the position of your car and whether reaching it is safe for a technician.
Three queries come first, before any quote, rather than after — what went in, how much, has it run — and this is the reason. A range turns into a straight figure once those answers are in.
About North End and its setting
North End is a suburban area in Greater London, situated approximately 13.8 miles from central London and 12.4 miles from the city centre. North End is characterized by its flat landscape, with an elevation of around 9 metres, and is predominantly composed of flat housing. North End is located near other suburban areas, including Slade Green, Colyers, and Barnehurst, and has a population of around 10,529 residents.
Fuel drain cover across Greater London, North End included
Slade Green, Colyers and Barnehurst are among the spots around North End that the same teams work, answering petrol in diesel calls across North End's DA postcode area. Our engineers drain where your vehicle is — your own drive, a lay-by, a supermarket car park, a forecourt — so it never needs to come to us.
At the petrol pump in North End, right now?
Nothing beats it: that's where you are. Leave the vehicle switched off, then ring.