Should You Worry? Petrol in a Diesel Car in Bubblewell
Probably less than you already are — provided no one has started it. Until the ignition primes your pump, your starter cranks, or the vehicle is driven, petrol in a diesel tank simply rests there and does nothing. Which means the honest reply to that first Bubblewell question — "have I ruined it?" — usually no. Leave your engine off and ring Petrol in Diesel — that keeps it that way. Below, you will find what petrol really does inside a diesel, how far it might have got, and how to stop it happening to you again.
Your engine and petrol in a diesel: what happens
Diesel does two tasks on its way through a motor. Oiling comes before burning; it does both. Made to extremely fine tolerances, the fuel injectors and the pump depend on your diesel flowing through them to keep their surfaces from wearing against one another.
The second job petrol does not do at all, and the first it does poorly. Being less viscous than diesel, petrol strips out the protection a fuel system needs, leaving a pump running on that mixture to wear itself. It's equally made to resist igniting under compression — the opposite of what a diesel needs — which is why you hear the clattering.
Put these together and the shape of the trouble is plain. Contact does not do the harm — circulation does. Petrol in a tank is a fuel fault. The start of a mechanical problem is a pump that has been labouring on that petrol — and whatever a worn pump sheds moves on with your fuel to the fuel injectors downstream.
Four scenarios our engineers see in Bubblewell: how serious is petrol in a diesel?
Filled up, never started. The best case there is. Just your tank has petrol in it, so the task is draining that tank and purging the fuel system where your car sits. This scenario can only truly occur on a forecourt: anywhere else, your car got there by being driven.
Ignition on, or started for a moment. With your system primed, the lines and filter now contain petrol that has come from your tank. That's generally still a simple job — a drain, a flush, and the fuel filter dealt with.
Driven a couple of miles. Now your pump has spent those miles running on diluted fuel. How hard the car was driven matters as much as how far, and this work takes in the tank, the fuel lines, the fuel filter and clean fuel through the entire circuit. Short trips, like the school run to Minchinhampton Primary Academy, are one thing. Very different once more: a run to Gloucester, under 15 miles away, or some miles on the M5, under 10 miles from Bubblewell, where your engine never stopped working hard.
Clattering, a ragged idle, smoke, a throttle gone soft: driven till it complained. The engine is telling you your fuel is no longer acting like diesel. Stop wherever you are — the verge on Well Hill, a lay-by, a side street — and leave the car there. The drain and flush still come first, and they take care of it: when a car is stopped early, long-term damage is very rare.
What Bubblewell drivers get told about petrol in a diesel — and the myths in it
Myth: "Fill it the rest of the way with diesel and it'll be fine." It will not. Nothing is removed when you top up — that tank just holds more of the same mixture. That advice supposes a diesel fuel system tolerates petrol by percentage. It does not.
If anything, the reverse holds. Myth: "A modern diesel can cope with a bit of petrol." A newer diesel runs its fuel through smaller components at higher pressure, which makes the protection matter more, not less.
"It starts, it drives, and so no harm done" — the myth that trips up most drivers than any other. Feed diesel to a petrol motor and it usually will not run, so the motorist stops — and the harm stops with them. Feed petrol to a diesel and it usually fires up, idles and drives away as if nothing has happened — all the while its pump wears. Being able to run is not the same as being fine.
"A drop of two-stroke oil and drive it home" — a myth, taken from a fix from years ago, for a separate issue. The petrol is still in the tank afterwards, and what it has diluted is not put back.
Once the engine has been run, part of the petrol is in the filter and the fuel lines, not that tank — and your next start pulls it straight back through your pump. So the myth "drain the tank yourself and you're sorted" does not stand up. Draining petrol into a can by the roadside is also really hazardous.
How it happens: petrol in a diesel
It is rarely carelessness, and nobody does it on purpose. One way only, since of the nozzles: the narrower petrol one slips inside a diesel filler with almost no resistance, while the diesel one generally won't fit a petrol vehicle. That is how the forecourt makes it simple.
When routine and your car stop matching, it takes place. Hire cars, courtesy cars, and cars that are new to you. Two cars on one drive, one petrol, one diesel. Your usual forecourt, its pumps now in a different order. Filling up in a rush en route to Stroud, with a train to catch. Years of petrol motors behind you, a diesel Volkswagen Golf in front of you at the forecourt for its first tank — that's when. Add rain, a phone call or a back seat full of kids, and your hand repeats what it has always done.
Bubblewell people: how to prevent petrol in a diesel next time
- 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 just a hint.
- Many vehicles state the fuel inside your filler flap or on the cap, so check there on the first fill in a vehicle you don't know.
- One of each in the household? Label the key to your diesel — a bright fob, a sticker — because meaning to remember is not enough.
- Before the nozzle comes off the pump the first time you fill a hired or new motor, say "diesel" aloud. Silly, yes, but it does the trick.
- Tuck your phone away. This is an easy mistake to make while you are thinking about something else.
- Some diesels have a filler built to reject a petrol nozzle, and devices you can add are available for vehicles without one. Such an inhibitor helps up to a point — as a safety net, not a reason to stop checking the pump.
- As soon as you realise, stop: less petrol in that tank makes a weaker blend. What to do next does not change, though — still do not start it.
Petrol already in a diesel in Bubblewell? Begin here
Short and simple, then, is the order of things. Don't turn your ignition on, and do not crank it. The attendants on the forecourt — whether at Shell itself or wherever you filled up — will normally help push it clear of the petrol pump if you ask. Next, 0333 366 0103. We will ask what went in, about how much, and if it has been run.
Corrosion and deposits are the trouble with AdBlue, where petrol brings lost protection. So if it was AdBlue, say so — and read its own Bubblewell page.
Bubblewell petrol in a diesel tasks: why one costs more than another
The four scenarios above are four separate jobs, so no single price for this would be fair. Which of them you are in is mostly what moves your cost. Beyond that it is the share — how much petrol got in against how much the tank holds — and after that where the car is and whether our van can reach it safely.
What was put in, how much, and whether it's run — three queries our technicians ask before quoting, not after, for exactly that reason. Those replies change a range into a straight figure.
About Bubblewell itself
Bubblewell is a suburban area in Gloucestershire, situated inland at an elevation of around 150 metres. Bubblewell lies approximately 11.7 miles from Gloucester and 89.3 miles from London, placing it in a commuter belt with access to larger cities. Bubblewell has a population of around 806 people, predominantly living in terraced housing. Bubblewell is near other small communities such as Forwood, Minchinhampton, and Balls Green.
Bubblewell and Gloucestershire: where our fuel drain cover runs
Bubblewell waits in the GL postcode area, and our vans that answer petrol in diesel call-outs there work the places near it as well — Forwood, Minchinhampton and Balls Green among them. A forecourt, a supermarket car park, a lay-by or your own driveway are all spots our technicians work, and the car doesn't need to come to us.
In Bubblewell and still at the petrol pump?
Then you are in the best spot there can be. Phone, and keep it switched off.