Boston: Petrol in a Diesel Car? How Worried to Be
Far less than you probably are, provided it has not been started. Everyone in Boston starts with "have I ruined it?", and the honest answer is generally no: petrol left in the tank of a diesel remains harmless until priming, cranking or driving draws it into the system. Keep it that way: leave the motor off then ring Petrol in Diesel. What petrol actually does to a diesel, how to gauge how far it's travelled, and how to keep it from happening a second time: that is the remainder of this page.
The engine and petrol in a diesel: what goes on
Passing through an engine, diesel is doing two jobs at once. Lubricating comes before burning; it does both. The high-pressure pump and your injectors are built to extremely fine gaps, and the diesel passing through them is what keeps those surfaces from wearing down against each other.
Of those two tasks, petrol manages the first poorly and the second never. Being less viscous than diesel, petrol strips away the protection a fuel system needs, so a pump on the blend to wear itself. It's equally made to resist igniting under compression — the reverse of what a diesel needs — which is why you hear the clattering.
Taken together, they make clear the shape the trouble takes. Contact does not do the harm — circulation does. Petrol in a tank is a fuel fault. Once your pump has been running on that petrol, a mechanical issue has started: anything shed by a pump that is wearing down is carried downstream to the fuel injectors with the fuel.
How serious is petrol in a diesel? Four scenarios our engineers see in Boston
The best case there can be: filled up, not once started. At a forecourt, and genuinely only there, that petrol is still confined to your tank — since everywhere else your car was driven to get to it. The task is draining and flushing on the spot.
A brief spell of running, or just the ignition on. Petrol has come out of the tank and got to the fuel filter and the lines, since the system has been bled. Normally nothing more than emptying, purging and sorting your filter, so still straightforward.
Driven a few miles. Now your pump has spent these miles labouring on weakened fuel. How hard the car was driven matters as much as how far, and this work takes in the tank, your lines, the fuel filter and fresh fuel through the entire system. Short trips, such as the school run to Boston Pioneers Free School Academy, are one thing. Any miles on the A1(M), under 50 miles from Boston, means the motor working hard throughout, and a run to Lincoln, under 50 miles away, is a very different task too.
Driven on till it protested — rattling, smoke, a lumpy idle, a dead throttle. The fuel isn't acting like diesel any more, and your motor is telling you. Whether it's the verge on West Street, a lay-by or a side street, stop there and leave it. Lasting damage is very rare when a vehicle is pulled over early, and the fuel drain and flush-through that still come first deal with it.
Myths Boston motorists hear about petrol in a diesel
It will not be fine. The myth: "Fill it the rest of the way with diesel and it'll be." Nothing is removed by topping up — you are left with a fuller tank, still the same mixture. The idea behind the guidance — that diesel fuel systems tolerate petrol by percentage — is wrong.
Myth: a modern diesel copes with a bit of petrol. If anything, the opposite. Lubrication matters more on current diesels, not less, because their fuel passes through finer parts at higher pressure.
The myth that catches people off guard: if it starts and drives, it must be unharmed. A petrol motor fed diesel usually won't run, so the driver stops and the harm stops with them. A diesel fed petrol generally starts, ticks over and drives away as though nothing has happened, while your pump grinds. Running doesn't mean fine.
Myth: "Add some two-stroke oil and drive the car home." It is an old workaround for a distinct fault. What petrol has weakened remains weakened, and the petrol stays in that tank regardless.
Myth: "Drain the tank yourself and you are sorted." After the motor has run, some of that petrol is no longer inside that tank: it's in your filter and the lines, and it goes straight back through your pump at your next start. Besides, petrol emptied into a can by the road is truly risky.
How does petrol in a diesel take place?
Carelessness is seldom the cause, and nobody means to do it. A diesel nozzle generally won't go into a petrol car, yet the slimmer petrol nozzle goes into the filler of a diesel almost without resistance — so forecourts make this one mistake simple, and just in one direction.
Routine and the vehicle getting out of step is when it occurs. Courtesy car, hire car, or a motor that's new. One petrol and one diesel on the driveway of the same household. The pumps in a different order on a well-known forecourt. A hurried fill on the way to the nearest station with a train to catch. Years of petrol cars behind you, a diesel Volkswagen Golf in front of you at the forecourt for its first tank — that is when. Throw in a back seat full of kids, a phone call or rain, and the hand takes over.
How to prevent petrol in a diesel at your next fill-up in Boston
- Read the petrol pump, not the colour. In the UK unleaded handles are generally green and diesel black, but not on each forecourt. The label is what matters.
- The first fill in an unfamiliar car is the time to check your filler flap — on it, or on the cap, many motors state which fuel to use.
- A coloured fob or a sticker on the diesel's key does more than any amount of meaning to remember, for a household with one of each.
- "Diesel", aloud, before you lift the nozzle — every time a new or hired car gets its first tank. It seems silly. It works.
- Thinking about something else is when this becomes an easy mistake to make, and so tuck the phone away and keep your mind on the petrol pump.
- A misfuel inhibitor helps, up to a point. Some diesels have a filler built to reject a petrol nozzle, and add-on devices are available for cars without one. They are a backstop, not a reason to stop reading the petrol pump.
- Spotting it halfway? Stop at once. A thinner mix results from less petrol in your tank, but the next step remains the same: don't start the vehicle.
Boston: already put petrol in a diesel?
The order of things is brief, then. Starting it is out, and so is turning on the ignition. Ask the attendants to help you push it clear of the pump if you are still on the forecourt, whether that's Asda or anywhere else. Next, 0333 366 0103. We'll ask what got in, about how much, and if it's been run.
Say so if it was AdBlue instead of petrol: it's a different problem, with its own page for Boston, since AdBlue brings corrosion and deposits rather than lost lubrication.
One petrol in a diesel task around Boston costs more than another. Why?
Four separate tasks sit behind the four situations above — which is why there is no honest single price. Mostly, the cost shifts with which one you're in. Two things follow that: the petrol that got in as a share of what your tank holds, then the place the car is in and whether a van can reach it safely.
That's why our technicians ask three queries before quoting instead of after: what went in, how much, and if it has run. Their answers are what change a range into one firm number.
About Boston, for a moment
Boston is a town situated in a riverside location in Lincolnshire, England. It is positioned near several major cities, including Lincoln, Nottingham, and Peterborough. The town is notable for its inland port and its connection to the Lincolnshire coast via The Haven. Boston's setting makes it a distinctive place in the region.
Across Lincolnshire and in Boston: fuel drain cover
Petrol in diesel calls around Boston — part of the PE postcode area — go to vans that likewise cover the locations round it, Skirbeck Quarter, Skirbeck and Burton Corner among them. No need to bring the car to us. Forecourts, supermarket car parks, lay-bys and your own driveway are all spots we drain.
In Boston and still at the petrol pump?
No position is better: that's where you are. Keep it off. Ring.