Blue Anchor: Petrol in a Diesel Car? How Worried to Be
Provided it has not been started, worry far less than you probably are. Until your ignition primes your pump, the starter cranks, or the vehicle is driven, petrol in a diesel tank simply waits there and does no harm. Which makes the truthful reply to that first Blue Anchor query — "have I wrecked it?" — normally no. Keep it that way: leave your engine off and call Petrol in Diesel. Read on for three things: the effect petrol has inside a diesel motor, the signs of how far it has spread, and ways to make sure you never do it again.
What petrol in a diesel does to the motor
Passing through an engine, diesel is doing two things at the same time. Lubricating comes before burning; it does both. What stops the surfaces inside your high-pressure pump and the injectors from wearing against one another is your diesel flowing through them — they're made to extremely fine clearances.
Petrol does the first job badly and the second not at all. A pump running on a petrol mixture is wearing itself out, since petrol is runnier than diesel and strips out the lubrication your fuel system relies on. Petrol is also made to resist igniting under compression — the reverse of what a diesel wants from its fuel — and that is where any rattling starts.
Seen together, they show the shape the problem takes. It is movement that does the harm, not contact. All a tank with petrol in it amounts to is a fuel issue. The start of a mechanical problem is a pump that has been running on that petrol — and whatever a worn pump sheds travels on with the fuel to the fuel injectors beyond it.
Four scenarios we see in Blue Anchor: how bad is petrol in a diesel?
Fuelled but not once started — the best it gets. On a forecourt, and genuinely only there, that petrol is still limited to your tank — because anywhere else the car was driven to get to it. The job is draining and rinsing on the spot.
Ignition on, or started for a second. Once primed, the fuel system has pulled petrol out of the tank as far as the filter and the fuel lines. Normally nothing more than draining, flushing and seeing to your filter, and so still straightforward.
Your pump now worked a few miles on diluted fuel — that's what driving it meant. How hard the car was driven counts as much as how far, and this work covers your tank, the lines, your filter and clean fuel through the whole system. A school run to the local primary school is one thing. A run as far as Swansea, under 10 miles away, is a very different job. So is any mileage on the M4, under 5 miles from Blue Anchor, where the engine has been labouring hard throughout.
Rattling, a ragged idle, smoke, a throttle gone soft: driven until it complained. That's the motor telling you its fuel no longer is acting like diesel. Leave it wherever it has stopped: a lay-by, a side street, the verge on Blue Anchor Road. The drain and flush still go first, and they take care of it: when a vehicle is stopped soon, lasting damage is very rare.
Blue Anchor motorists and that petrol in a diesel stories they hear
It will not be fine. The myth: "Fill it the rest of the way with diesel and it will be." A bigger tank of the same mixture is all it gives, because topping up removes nothing. That advice assumes a diesel fuel system tolerates petrol by percentage. It does not.
"Newer diesels can handle a little petrol" — a myth, and closer to the opposite. More precise components and higher pressure are how a current diesel runs its fuel, and that makes the protection count more, not less.
The myth that catches people out: if it starts and drives, it must be unharmed. Diesel in a petrol motor normally leaves a motor that won't run: the driver stops, and so does the damage. A diesel fed petrol usually starts, idles and drives away as if nothing has happened, while the pump grinds. Fine and running aren't the same at all.
An outdated fix for a separate fault lies behind this one. Myth: "Add some two-stroke oil and drive the vehicle home." It doesn't put back what petrol has thinned, and that petrol is still in the tank later on.
"Drain it yourself and you are sorted" — a myth, because after it's been running some petrol lies in your filter and lines, waiting to go right back through your pump on the next start. On top of that, petrol cleared into a can by the road is genuinely dangerous.
Petrol in a diesel: how does it happen?
Carelessness is rarely the cause, and nobody means to do it. A diesel nozzle mostly won't go into a petrol vehicle, but the slimmer petrol nozzle goes into the filler of a diesel almost without resistance — so forecourts make this one error straightforward, and just in that direction.
It occurs when habit and the vehicle stop matching. Hire cars, courtesy cars, and motors that are new to you. Two motors on one drive, one petrol, one diesel. Your normal forecourt, its pumps now in a different order. Racing for a train at Bynea and filling up en route. Years of petrol motors behind you, a diesel Volkswagen Golf in front of you at the forecourt for its first tank — that's when. Throw in rain, a phone call or a back seat full of kids, and the hand repeats what it has always done.
Next time you fill up around Blue Anchor: avoiding petrol in a diesel
- Not every forecourt in the UK keeps to green for unleaded and black for diesel, even if most usually do. Read the pump's label; the colour is just a hint.
- In a motor you don't know, look inside the flap over the filler or at the cap before the first fill: many cars state the fuel type there.
- Good intentions do less than a sticker or a fob in a vivid colour on the diesel's key when a household has one of each. So mark it.
- "Diesel", aloud, before you pick up the nozzle — each time a new or hired car gets its first tank. It sounds silly. It does the trick.
- Mistakes like this are straightforward to make while your mind is on something else, and so the phone goes away.
- A misfuel inhibitor helps, up to a point. Some diesels have a filler built to block a petrol nozzle, and add-on devices are available for motors without one. They are a backstop, not a reason to stop reading the petrol pump.
- Stop the moment you notice. Less petrol in your tank means a thinner mixture. It does not change what to do next, which is still not to start it.
Already put petrol in a diesel around Blue Anchor?
The order of things is short, then. Don't switch the ignition on, and do not fire it up. The staff at the forecourt — whether at Tesco itself or wherever you filled up — will usually help roll it away from the pump if you ask. What got in, about how much, and if it has run: tell us those when you call 0333 366 0103.
Say so if it was AdBlue instead of petrol: it is a separate fault, with its own page for Blue Anchor, because AdBlue brings corrosion and deposits rather than lost lubrication.
Blue Anchor petrol in a diesel tasks: why one costs more than another
There is no fair single price for this, since the four situations above are four separate jobs. Which of them you're in is chiefly what moves your cost. Beyond that it is the proportion — how much petrol was put in against how much your tank takes — and then where the car is and whether our van can reach it safely.
That is why our engineers ask three questions before quoting rather than after: what was put in, how much, and if it has run. A range turns into a straight figure once the answers are in.
About Blue Anchor itself
Blue Anchor is a small coastal village in Swansea, situated near the coast at an elevation of 69 metres. Blue Anchor lies approximately 6.8 miles west of Swansea and is surrounded by nearby places such as Pen-y-Lan and Parc-hendy. Blue Anchor has a population of around 552 people and predominantly consists of semi-detached housing. Blue Anchor is located within a short distance of other local communities, including Wernbwll.
Fuel drain cover around Blue Anchor and across Swansea
Pen-y-Lan, Parc-hendy and Wernbwll are among the spots near Blue Anchor that the same vans work, answering petrol in diesel jobs across Blue Anchor's SA postcode area. We drain wherever the car is — your own drive, a lay-by, a supermarket car park, a forecourt — so it does not have to come to us.
Still at the petrol pump around Blue Anchor?
No position is better: that is where you now are. Switched off it stays; then phone.