Armitage: Petrol in a Diesel Car? How Worried to Be
If it hasn't been started, you can worry far less than you probably are. Everyone around Armitage starts with "have I ruined it?", and the fair answer is normally no: petrol left in that tank of a diesel remains harmless until priming, cranking or driving pulls it into your fuel system. Leave the motor off then call Petrol in Diesel — that keeps it that way. Further down, you will find what petrol really does inside a diesel, how far it might have gone, and how to stop it happening to you a second time.
Petrol in a diesel: what does it do to the motor?
Two tasks fall to diesel on its journey through a motor. Before it burns, it protects — and then it ignites. Designed to very fine tolerances, your injectors and the pump rely on your diesel flowing through them to keep their surfaces from wearing against one another.
Of those two jobs, petrol manages the first poorly and the second not at all. A pump running on a petrol mixture is wearing itself out, because petrol is runnier than diesel and strips out the protection your 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 comes.
The shape of the issue is plain once you put those together. Not contact but movement is what does the damage. Petrol in the tank is a fuel problem. The start of a mechanical one is a pump that has been working on that petrol — and whatever a worn pump sheds travels on with your fuel to the injectors downstream.
How serious is petrol in a diesel? Four situations our technicians see around Armitage
Fuelled, and not started: nothing beats it. The petrol is in that tank and just your tank, and the job is a drain and a flush where the car stands. This is the one scenario that can only truly occur on a forecourt, because anywhere else the car has been driven to get there.
A moment's running, or merely your ignition on. The fuel system has been bled, so petrol has left your tank and reached the fuel filter and the lines. Still normally straightforward: drain, flush, and your filter dealt with.
Driven a couple of miles. Now your pump has spent these miles labouring on diluted fuel. The work is the tank, the fuel lines, the fuel filter and clean fuel through the whole system, and how hard the vehicle was driven counts as much as how far. Short trips, like the school run to The Croft Primary School, are one matter. Very different a second time: a trip to Lichfield, under 5 miles away, or some distance on the M6 Toll, under 10 miles from Armitage, where the motor never stopped labouring hard.
Driven on till it complained — knocking, smoke, a ragged idle, a dead throttle. What you are hearing is the motor signalling fuel that no longer behaves like diesel. Whether it's the verge on New Road, a lay-by or a side street, stop there then leave it. What goes first is still the drain and flush-through, and that sorts it out, with lasting damage very unusual if a vehicle is pulled over quickly.
Petrol in a diesel myths Armitage people hear
Myth: "Fill it the rest of the way with diesel and it'll be fine." It will not. A fuller tank of the same mixture is all you get, because topping up removes nothing. Percentage isn't how a diesel fuel system tolerates petrol, whatever that advice presumes.
If anything, the opposite holds. Myth: "A current diesel can cope with a bit of petrol." At higher pressure, through smaller parts: that's how a newer diesel handles its fuel, and so the protection counts more, not less.
This is the one that catches people. Myth: "If it starts and drives, there's no harm done." The motorist of a petrol motor fed diesel usually stops, since it will not run, and the damage stops with them. While the pump wears, a diesel fed petrol normally starts, ticks over and drives away as though nothing has happened. A running engine does not mean fine.
Myth: a two-stroke additive lets you to drive home. It was an old workaround, meant for another problem. The petrol is still inside the tank after that, and whatever it has weakened isn't put back.
Myth: "Drain that tank yourself and you're sorted." After the engine has run, some of the petrol is no longer in the tank: it is in your filter and the lines, and it goes right back through your pump on the next start. It's also really risky to drain petrol into a can at the kerbside.
Petrol in a diesel: how does it take place?
It is seldom carelessness, and no one does it on purpose. The petrol nozzle is the slimmer of the two and slides into a diesel filler with almost no resistance; a diesel nozzle generally won't go into a petrol car at all. The forecourt makes it easy, and the error runs one way.
The moment habit stops matching the car is the moment it occurs. Courtesy car, hire car, or a motor that's new. A household with one petrol and one diesel on the drive. A forecourt you know, but with its pumps laid out differently. Fuelling up in a rush en route to Rugeley Town, with a train to catch. Years of petrol vehicles behind you, a diesel Volkswagen Golf in front of you on the forecourt for its first tank — that's when. With rain, a call arriving, or a car full of children to deal with, the hand just does what it always has.
How to avoid petrol in a diesel at your next fill-up in Armitage
- Read the petrol pump, not the colour. In the UK unleaded handles are generally green and diesel black, yet not on each forecourt. The label is what counts.
- The first fill in an unfamiliar motor is the time to check your filler flap — on it, or on the cap, plenty of vehicles state which fuel they take.
- Mark the key. In a house with one of each, a coloured fob or a sticker on your diesel's key does more than any amount of meaning to remember.
- Before the nozzle leaves the petrol pump the first time you fill a hired or new vehicle, say "diesel" out loud. Silly, perhaps, but it works.
- Mistakes like this are simple to make while your mind is on something else, so your phone goes away.
- Up to a point, a misfuel inhibitor helps: some diesels come with a filler built to block a petrol nozzle, and add-on devices are available for the rest. Count it as a safety net, and keep reading the petrol pump.
- Less petrol makes a thinner blend, so stop as soon as you realise — though remembering that the next step is unchanged. It's still not to fire it up.
Armitage: already put petrol in a diesel?
Short and simple, then, is the order of things. Starting it is out, and so is switching on your ignition. Ask the attendants to help you push it away from the pump if you are still at the forecourt, whether that is Esso or somewhere else. Phone 0333 366 0103 next, with three facts — your fuel, the rough quantity, and if it has run.
AdBlue, not petrol? Then say so. Corrosion and deposits, not lost protection, make it a separate problem — Armitage has a page all for it.
One petrol in a diesel job around Armitage costs more than another. Why?
An honest single price does not exist here: four scenarios, four separate tasks. Chiefly, the cost moves with which situation you are in. Where the vehicle is matters too, and whether a van can safely get to it, after the ratio of petrol to what that tank takes.
Three questions come first, before any quote, instead of after — what was put in, how much, has it run — and this is the reason. The answers turn a range into a straight figure.
About Armitage itself
Armitage is a village in Staffordshire, situated on the banks of the River Trent at an elevation of 79 metres. Armitage lies near the city of Lichfield, with neighbouring villages including Handsacre and Mavesyn Ridware. Armitage has a population of approximately 1735 people, predominantly living in semi-detached housing. Armitage is located about 113 miles northwest of London, in the West Midlands region.
Fuel drain cover in Armitage and across Staffordshire
Armitage waits in the WS postcode area, and our vans that answer petrol in diesel call-outs there work the spots around it as well — Handsacre, Mavesyn Ridware and Tuppenhurst 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.
Armitage: still at the petrol pump?
No position is better: that's where you now are. Keep the car switched off, and ring.