Petrol in a Diesel Car in Coagh: How Worried Should You Be?
Unstarted? Then less anxious than you probably are. Until your ignition primes your pump, your starter turns, or the vehicle is driven, petrol in a diesel tank simply rests there and does nothing. Which makes the honest reply to that first Coagh question — "have I ruined it?" — usually no. Keep it like that: leave the engine off and ring Petrol in Diesel. Read on for three things: the effect petrol has inside a diesel engine, the clues of how far it has spread, and ways to make sure you don't do it again.
Inside the engine: what petrol in a diesel really does
Passing through an engine, diesel is doing two jobs at the same time. Lubricating comes before burning; it does both. Designed to very fine tolerances, your injectors and your pump rely on your diesel moving through them to stop their surfaces wearing against one another.
Petrol does the first task badly and the second not at all. Being less viscous than diesel, petrol strips out the lubrication a fuel system needs, so a pump on the mixture wearing itself. It's also made to resist igniting under compression — the reverse of what a diesel needs — which is where you hear the rattling.
Put those together and the shape of the problem is plain. Contact does not do the damage — movement does. Petrol in a tank is a fuel fault. After the pump has been labouring on that petrol, a mechanical problem has started: whatever is shed by a pump that's wearing travels downstream to your injectors with the fuel.
Four scenarios our technicians see around Coagh: how bad is petrol in a diesel?
Fuelled, and never started: nothing beats it. Only that tank has petrol in it, and so the task is emptying your tank and purging the system where your car sits. This situation can only really happen at a forecourt: anywhere else, your car got there by being driven.
Started for a second, or only your ignition on. Once primed, your system has drawn petrol from your tank as far as the fuel filter and the fuel lines. Drain, flush, deal with the fuel filter: still normally straightforward.
Those few miles on the road were your pump working on fuel weakened by petrol throughout. Distance is only half of that; how hard it was driven counts just as much. Either way this work runs to your tank, the lines, your filter and fresh fuel through the entire system. On the school run to the local primary school, the mileage is short. Driving as far as Armagh, under 25 miles away, makes a very different task — as does any miles on the M77, over 50 miles from Coagh, with the motor running hard all the way.
Driven on until it complained — clattering, smoke, a lumpy idle, a dead throttle. What you are hearing is the motor reporting fuel that no longer runs like diesel. Whether it is the verge on B842, a lay-by or a side road, stop where you are and leave it. Lasting damage is very rare if a car is pulled over early, and the fuel drain and flush that still come first sort it out.
Stories Coagh motorists hear about petrol in a diesel
"Top it up the rest of the way with diesel and it'll be fine" — a myth. It will not. Topping up removes nothing; it gives you a bigger tank of the same mix. A diesel fuel system doesn't accept petrol by percentage in the way that guidance presumes.
Myth: "A modern diesel can cope with a bit of petrol." If anything, the reverse. At higher pressure, through finer parts: that is how a newer diesel moves its fuel, so the protection counts more, not less.
One myth that catches drivers off guard: if it starts and drives, it must be unharmed. Diesel in a petrol motor usually means a motor that won't run: the driver stops, and so does the damage. Whilst the pump wears, a diesel fed petrol normally starts, ticks over and drives away as though nothing has happened. Fine and running are not the same at all.
Myth: "Add some two-stroke oil and drive it home." It is an old fix for a different problem. What petrol has diluted remains weakened, and the petrol remains inside the tank anyway.
Myth: "Drain the tank yourself and you are sorted." After your engine has run, some of that petrol is no longer in the tank: it's in your filter and the fuel lines, and it goes straight back through the pump on the next start. It is also really risky to drain petrol into a can at the roadside.
How does petrol in a diesel happen?
On purpose? Never. Through carelessness? Seldom, if ever. A diesel nozzle mostly will not go into a petrol motor, yet the slimmer petrol nozzle goes into the filler of a diesel nearly without resistance — so forecourts make this one error simple, and just in that direction.
It occurs when routine and the car stop matching. Any car that is new to you — hired, on loan as a courtesy car, or just bought. A household with one petrol and one diesel on the driveway. The pumps in a different order on a familiar forecourt. A train to catch, and a hurried fill on the way to the nearest station. The first fill-up in a diesel Volkswagen Golf after years of driving petrol is exactly the moment it occurs. Throw in a back seat full of children, a phone call or rain, and the hand takes over.
How to avoid petrol in a diesel on your next fill-up in Coagh
- Not every forecourt in the UK keeps to green for unleaded and black for diesel, though most generally do. Read the pump's label; the colour is only a clue.
- Many cars state the fuel inside your filler flap or on the cap, and so check there on the first fill in a vehicle you don't know.
- 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.
- Before the nozzle leaves the petrol pump the first time you fuel a hired or new vehicle, say "diesel" out loud. Daft, yes, yet it works.
- Thinking about something else is when this becomes an easy mistake to make, and so tuck the phone away and keep your mind on the pump.
- Up to a point, a misfuel inhibitor helps: some diesels come with a filler designed to block a petrol nozzle, and add-on devices exist for the remainder. Count it as a safety net, then keep reading the pump.
- Stop as soon as you realise. Less petrol inside the tank means a thinner mixture. It does not change what to do next, which is still not to crank it.
Petrol already in a diesel in Coagh? Start here
Then the order of things is short. Don't crank it, and do not turn your ignition on. If you are still at the forecourt — the nearest petrol station or anywhere else — ask the attendants to help you push the car clear of the pump. What got in, roughly how much, and whether it has run: tell us that when you phone 0333 366 0103.
Say so if it was AdBlue rather than petrol: it's a separate issue, with its own page for Coagh, because AdBlue brings corrosion and deposits rather than lost lubrication.
What makes one Coagh petrol in a diesel task cost more than the next
There's no fair single quote for this, since the four situations above are four different jobs. What moves your cost is mostly which of them you're in. Two things follow that: the petrol that got in as a proportion of what that tank holds, then the place the vehicle is in and whether our van can reach it safely.
Before any quote, not after, we ask three queries: the fuel that went in, the amount, and whether it has run. That is why. Given the answers, you get a straight figure instead of a range.
About Coagh, briefly
Coagh is a small locality in County Tyrone, situated inland at an elevation of 38 metres, approximately 20 miles from Armagh. Coagh lies near several other small settlements, including Drummullan, Derrycrin, and Moneymore, and is characterized by its semi-detached housing stock. Coagh is a relatively small community, with a population of around 816 people, and is located about 345 miles northwest of London.
Fuel drain cover across County Tyrone, Coagh included
Petrol in diesel calls in Coagh — part of the BT postcode area — go to teams that likewise cover the spots around it, Drummullan, Derrycrin and Moneymore among them. Our engineers drain wherever the vehicle is — your own driveway, a lay-by, a supermarket car park, a forecourt — so it does not have to come to us.
Coagh: still at the petrol pump?
The best position there is, then — that's where you are. Phone, and keep it turned off.