Lochmaben: Petrol in a Diesel Car? How Worried to Be
Likely less than you are now — provided nobody has started the vehicle. Petrol sitting in a diesel tank does nothing to the engine till something pulls it through the system — your ignition priming the pump, your starter, or the drive on its own. So the fair answer to the first question anyone in Lochmaben asks, "have I ruined it?", is normally no. Petrol in Diesel is who to phone, with the motor left off, and so it stays that way. Keep reading 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 never do it again.
What petrol in a diesel does to your engine
Passing through a motor, diesel is doing two jobs at once. Oiling comes before burning; it does both. What stops the surfaces inside the high-pressure pump and the injectors from wearing against one another is the diesel flowing through them — they're made to very fine tolerances.
Petrol does the first task poorly and the second not at all. A pump working on a petrol mixture is wearing itself out, because petrol is thinner than diesel and strips out the lubrication the fuel system relies on. Petrol is also made to resist igniting under compression — the reverse of what a diesel needs from its fuel — and that is where any clattering starts.
Seen together, they make clear the shape the issue takes. Not contact but circulation is what does the damage. Where the petrol is only inside your tank, it's an issue of fuel, nothing more. Whatever a worn pump sheds travels on, borne by the fuel, into the fuel injectors further along, which is why a pump that has worked on that petrol is where a mechanical problem starts.
Petrol in a diesel in Lochmaben: how bad is it? Four cases
The best case there can be: filled up, not once started. That petrol is in the tank and only the tank, and the task is a drain and a flush where your car sits. This is the one scenario that can only truly happen on a forecourt, since anywhere else the car has been driven to get there.
Started for a second, or only your ignition on. With your system primed, the lines and filter already contain petrol that came from that tank. Drain, flush, see to the fuel filter: still normally easy.
Driven a few miles. Now your pump has spent those miles labouring on weakened fuel. How hard your car was driven matters as much as how far, and this work covers the tank, the fuel lines, your filter and clean fuel through the entire system. A school run to the local primary school is one matter. A run as far as Carlisle, under 50 miles away, is a very different job. So is any miles on the A74(M), under 3 miles from Lochmaben, where the motor has been running hard throughout.
Driven on until it complained — rattling, smoke, a lumpy idle, a soft throttle. That's the engine telling you its fuel no longer is behaving like diesel. Leave it where it stops: a lay-by, a quiet street, the verge on Castle Street. Long-term damage is very uncommon if a vehicle is stopped early, and the drain and flush-through that still come first sort it out.
Stories Lochmaben drivers 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. Nothing is removed when you top up — the tank just carries more of the same mixture. A diesel fuel system does not accept petrol by percentage in the way that advice supposes.
If anything, the opposite is true. Myth: "A modern diesel can cope with a bit of petrol." At higher pressure, through smaller components: that's how a modern diesel moves its fuel, and so the lubrication matters more, not less.
Myth: "If it starts and drives, there's no damage done." This is the one that catches people. Diesel in a petrol motor generally means a motor that won't run: the motorist stops, and so does the damage. Feed petrol to a diesel and it generally starts, ticks over and pulls away as if nothing happened — all while its pump wears. Fine and running aren't the same at all.
Not so: a two-stroke additive makes it safe to drive home. It was an old workaround, meant for another issue. What petrol has diluted remains diluted, and the petrol stays inside your tank anyway.
"Drain it yourself and you are sorted" — a myth, because after it has been running some petrol sits in the filter and lines, waiting to go straight back through your pump on the next start. It's also really dangerous to drain petrol into a can at the kerbside.
Why petrol in a diesel occurs so easily
It's rarely carelessness, and nobody does it on purpose. A diesel nozzle mostly will not fit a petrol motor, yet the narrower petrol nozzle goes into the filler of a diesel nearly without resistance — so forecourts make this one error easy, and just in one direction.
Routine and the vehicle falling out of step is how it takes place. Any car that's new to you — hired, 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 familiar forecourt. Fuelling up in a hurry on the way to Lockerbie, with a train to catch. Years of petrol vehicles behind you, a diesel Skoda Octavia in front of you on the forecourt for its first tank — that's when. Your hand does what it has always done once you add rain, a phone call or a back seat full of children.
Next time you fill up around Lochmaben: avoiding petrol in a diesel
- Check the petrol pump, not the colour. In the UK unleaded handles are usually green and diesel black, yet not on every forecourt. The label is what matters.
- The first fill in an unfamiliar motor is the time to check the filler flap — on it, or on the cap, plenty of motors state the fuel to use.
- Good intentions count for less than a sticker or a fob in a bright colour on your diesel's key if a household has one of each. So label it.
- Before the nozzle comes off the petrol pump the first time you fill a hired or new vehicle, say "diesel" out loud. Silly, yes, but it works.
- Tuck your phone away. This is an easy mistake to make whilst you're thinking about something else.
- Some diesels come with a filler designed to reject a petrol nozzle, and devices you can add are available for cars without one. Such an inhibitor helps up to a point — as a backstop, not a reason to stop reading the petrol pump.
- Spotting it mid-fill? Stop there and then. A weaker mix follows from less petrol inside your tank, yet the next stage remains the same: do not fire it up.
Lochmaben: already put petrol in a diesel?
The order of things is short, then. Do not switch your ignition on, and do not start it. The attendants on the forecourt — whether at the nearest petrol station itself or wherever you filled up — will usually help roll it away from the pump if you ask. Then ring 0333 366 0103 and tell us what got in, about how much, and if it has run.
AdBlue, not petrol? Then tell us. Corrosion and deposits, not lost lubrication, make it a separate issue — Lochmaben has a page just for it.
What makes one Lochmaben petrol in a diesel job cost more than the next
There's no honest single quote for this, because the four situations above are four different tasks. What moves the cost is chiefly which of them you are in. Where the vehicle is matters too, and whether a van can safely get to it, after the proportion of petrol to what your tank takes.
What got in, how much, and if it has run — three questions our engineers ask before quoting, not after, for precisely that reason. Given those answers, there is a straight figure rather than a range.
About Lochmaben and where it is
Lochmaben is a small town situated on the banks of the River Annan in Dumfries and Galloway, with a mix of detached housing and other residential properties. Lochmaben sits at an elevation of 56 metres, looking out over the surrounding countryside. Lochmaben is located near several smaller settlements, including Marjoriebanks, Halleaths, and Watchhill, and is approximately 25.9 miles from the city of Carlisle. Lochmaben has a population of around 2187 people, making it a relatively small but distinct community in the region.
Across Dumfries and Galloway and in Lochmaben: fuel drain cover
Marjoriebanks, Halleaths and Watchhill are among the places around Lochmaben that the same teams work, answering petrol in diesel calls across Lochmaben's DG postcode area. No need to move the car to us. Forecourts, supermarket car parks, lay-bys and your own drive are all places where we work.
In Lochmaben and still at the pump?
The best position there is, then — that is where you are. Turned off it stays; then call.