Should You Worry? Petrol in a Diesel Car in Cammo
Not started? Then less anxious than you likely feel. Everyone around Cammo starts with "have I wrecked it?", and the honest answer is generally no: petrol resting inside your tank of any diesel stays harmless till priming, cranking or driving draws it into the system. Leave your motor off and phone Petrol in Diesel — that keeps it like that. Below, this page sets out what petrol really does inside a diesel, how far it might have gone, and how to stop it happening to you again.
Your engine and petrol in a diesel: what happens
Passing through a motor, diesel is doing two things at once. It combusts, and before it combusts it lubricates. Your high-pressure pump and your injectors are made to very fine gaps, and the diesel passing through them is what stops those surfaces from grinding against one another.
Of these two tasks, petrol manages the first badly and the second not at all. Being less viscous than diesel, petrol strips away the protection a fuel system needs, so a pump on the blend wearing itself. It is equally made to resist igniting under compression — the reverse of what a diesel needs — which is where you hear the clattering.
The shape of the issue is plain when you put those together. The damage is done by movement, not by contact. Petrol in the tank is a fuel issue. The start of a mechanical one is a pump that has been running on that petrol — and whatever a worn pump sheds travels on with your fuel to the injectors beyond it.
Four scenarios our technicians see around Cammo: how bad is petrol in a diesel?
Filled but never started — as good as it gets. Only that tank has petrol in it, and so the job is draining the tank and rinsing the system where your car sits. This situation can only truly happen on a forecourt: anywhere else, your car got there by being driven.
Started for a second, or only your ignition on. The fuel system has been bled, so petrol has left the tank and got to the fuel filter and your lines. Drain, flush, see to your filter: still normally straightforward.
The pump has worked a couple of miles on diluted fuel — that is what driving the vehicle meant. Tank, lines, filter, then fresh fuel put through the entire circuit: that's the work, and the way the vehicle was driven counts as much as the miles. Short trips, such as the school run to the local primary school, are one thing. Very different a second time: a trip to Edinburgh, under 5 miles away, or some mileage on the M8, under 3 miles from Cammo, where the motor kept running hard.
It complained, and only then stopped: smoke, knocking, a throttle gone soft, an idle gone uneven. The motor is telling you your fuel is no longer acting like diesel. Whether it is the verge on Cammo Gardens, a lay-by or a side road, stop where you are and leave it. A car pulled over quickly very rarely has long-term damage, as the drain and the flush-through, which still go first, deal with it.
Petrol in a diesel stories Cammo drivers 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 are left with a bigger tank, still the same mixture. The idea behind the advice — that diesel fuel systems accept petrol by percentage — is wrong.
"Current diesels can handle a little petrol" — a myth, and closer to the opposite. Protection matters more on newer diesels, not less, since their fuel passes through more precise components at higher pressure.
The myth that catches motorists out: if it starts and drives, it must be unharmed. A petrol motor fed diesel normally will not run, and so the motorist stops and the damage stops with them. Nothing looks to have happened when a diesel fed petrol fires up, ticks over and drives away, as it usually will; meanwhile the pump wears. A running engine does not mean fine.
Myth: "Add some two-stroke oil and drive it home." It's an old fix for a distinct issue. It doesn't put back what petrol has weakened, and the petrol is still inside the tank later.
Once the motor has been run, part of the petrol sits in your filter and the lines, not that tank — and the next start sends it right back through your pump. So the myth "drain that tank yourself and you are sorted" doesn't hold. On top of that, petrol drained into a can by the road is truly dangerous.
How petrol ends up: petrol in a diesel
It is seldom carelessness, and no one does it on purpose. The petrol nozzle is the slimmer of the two and slips into a diesel filler with almost no resistance; a diesel nozzle mostly won't go into a petrol motor at all. The forecourt makes it simple, and the error runs one way.
It happens when routine and your car stop matching. Any car that is new to you — a hire car, on loan as a courtesy car, or brand new. A household with one petrol and one diesel on the drive. The pumps in a different order on a well-known forecourt. A train to catch, and a hurried fill on the way to Edinburgh Gateway. Exactly the moment it occurs: after years of driving petrol, someone fills a diesel Volkswagen Golf for the first time. The hand repeats what it has always done when you add rain, a phone call or a back seat full of kids.
Avoiding petrol in a diesel next time you fill up around Cammo
- Not every forecourt in the UK follows green for unleaded and black for diesel, though most usually do. Read the petrol pump's label; the colour is just a clue.
- Plenty of motors state the fuel type inside the filler flap or on the cap, and so check there on your first fill in a car you do not know.
- One of each in the household? Mark your key to the diesel — a bright fob, a sticker — since intending to remember isn't enough.
- Before the nozzle leaves the pump the first time you fill a hired or new vehicle, say "diesel" out loud. Silly, perhaps, yet it works.
- Whilst you're thinking about something else, this is an easy mistake to make — so put your phone away.
- Some diesels come with a filler designed to block a petrol nozzle, and devices you can add exist for cars without one. Such an inhibitor helps up to a point — as a backstop, not a reason to stop reading the petrol pump.
- Stop as soon as you realise. Less petrol inside the tank makes a weaker blend. It doesn't change what to do next, which is still not to fire it up.
Cammo: already put petrol in a diesel?
Then the order of things is short. Do not turn the ignition on, and do not start it. If you're still on the forecourt — Shell or anywhere else — ask the attendants to help you push it clear of the pump. Then ring 0333 366 0103 and tell us what was put in, about how much, and whether it has run.
Say so if it was AdBlue rather than petrol: it is a different issue, with its own page for Cammo, since AdBlue brings corrosion and deposits instead of lost lubrication.
One petrol in a diesel task around Cammo costs more than another. Why?
The four situations above are four different jobs, so no single price for this would be fair. Mostly, your cost shifts with which one you are in. Two things come after that: the petrol that got in as a share of what that tank holds, then the place the vehicle is in and whether a technician can get to it safely.
That is why our engineers ask three queries before quoting rather than after: what got in, how much, and if it's run. A range turns into a straight figure when those answers are in.
About Cammo, briefly
Cammo is a suburban area in the City of Edinburgh, situated near the coast at an elevation of 33 metres. Cammo lies approximately 4.9 miles northwest of Edinburgh's city centre, within commuting distance of the capital. Cammo is characterised by its predominantly detached housing stock, with nearby amenities in Barnton, Braepark, and Cramond Bridge. Cammo is home to around 2388 residents, according to recent estimates.
Across City of Edinburgh and around Cammo: fuel drain cover
Petrol in diesel call-outs around Cammo — part of the EH postcode area — go to vans that likewise cover the places around it, Barnton, Braepark and Cramond Bridge among them. Our engineers drain wherever your car is — your own driveway, a lay-by, a supermarket car park, a forecourt — so it never needs to come to us.
Cammo: still at the petrol pump?
Then, you couldn't be in a better spot. Turned off it remains; then phone.