How Worried Should You Be? Petrol in a Diesel Car in Springfield
Unstarted? Then less worried than you probably are. Everyone around Springfield begins with "have I ruined it?", and the fair answer is normally no: petrol resting inside that tank of a diesel remains harmless till priming, cranking or driving pulls it into your fuel system. Petrol in Diesel is who to call, with your engine kept off, so it remains that way. What petrol really does to a diesel, how to gauge how far it has travelled, and how to keep it from happening again: that's the remainder of this page.
The motor and petrol in a diesel: what happens
On its way through a motor, diesel does two jobs. It combusts, and before it combusts it protects. The high-pressure pump and the injectors are made to very fine clearances, and the diesel passing through them is what stops those surfaces from wearing against each other.
The second job petrol does not do at all, and the first it does poorly. It's thinner than diesel and strips away the lubrication the fuel system depends on, and so a pump running on a petrol mix is a pump wearing itself. And petrol is made to resist igniting under compression, which is the reverse of what a diesel needs from its fuel. That is where the knocking comes from.
Taken together, they show the shape the trouble takes. The harm is done by circulation, not by contact. Where the petrol is only in the tank, it is a fault of fuel, nothing more. A pump that has been labouring on that petrol is the start of a mechanical one, and whatever a worn pump sheds moves on with the fuel to the fuel injectors downstream.
Four scenarios our engineers see around Springfield: how bad is petrol in a diesel?
Fuelled but never started — the best it gets. Only that tank has petrol in it, and so the task is emptying the tank and purging the fuel system where the car stands. This scenario can only truly occur at a forecourt: anywhere else, your car got there by being driven.
A moment's running, or just the ignition on. With the system primed, the lines and filter already contain petrol that came from the tank. Drain, flush, see to the fuel filter: still usually straightforward.
Some miles driven, and the pump has spent each of them running on weakened fuel. Tank, lines, filter, then clean fuel run through the entire system: that's this work, and the way your car was driven matters as much as the mileage. On the school run to Orchard Academy, the mileage is short. Any mileage on the M1, under 3 miles from Springfield, means the motor has worked hard throughout, and a run to Milton Keynes, under a mile away, makes a very different task too.
Driven on till it complained — clattering, smoke, an uneven idle, a dead throttle. What you are hearing is your motor signalling fuel that no longer runs like diesel. Stop wherever you are — the verge on South Enmore Roundabout, a lay-by, a side street — then leave the car there. Permanent damage is very rare when a vehicle is pulled over quickly, and the fuel drain and flush that still go first take care of it.
What Springfield people get told about petrol in a diesel — and the stories in it
"Top it up the rest of the way with diesel and it'll be fine" — a myth. It won't. Topping up takes out nothing; it gives you a fuller tank of the same mix. The idea behind the guidance — that diesel fuel systems accept petrol by percentage — is wrong.
"Newer diesels can handle a little petrol" — a myth, and closer to the reverse. At higher pressure, through smaller parts: that's how a modern diesel moves its fuel, and so the lubrication counts for more, not less.
"It starts, it drives, so there is no harm" — the myth that trips up most people than any other. The driver of a petrol engine fed diesel normally stops, because it will not run, and the damage stops there. Nothing seems 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 doesn't mean fine.
"A drop of two-stroke oil and drive it home" — a myth, borrowed from a fix from years ago, for a different problem. The petrol is still in the tank after that, and whatever it has thinned is not put back.
Myth: "Drain that tank yourself and you're sorted." After your engine has been run, some of the petrol is no longer in that tank: it is in the filter and the lines, and it goes straight back through the pump on the next start. Draining petrol into a can by the kerbside is also truly hazardous.
How petrol ends up: petrol in a diesel
It's rarely carelessness, and no one does it on purpose. One way only, since of the nozzles: the slimmer petrol one slides inside a diesel filler with almost no resistance, whereas the diesel one mostly will not fit a petrol motor. That is how the forecourt makes it simple.
It happens when routine and the car stop matching. Courtesy car, hire car, or a vehicle that's new. A household with one petrol and one diesel on the drive. Your normal forecourt, its pumps now in a different order. Rushing for a train at Milton Keynes Central and filling up en route. Precisely the moment it occurs: after years of driving petrol, a driver fills a diesel Volkswagen Tiguan for the first time. With rain, a call arriving, or children to deal with, the hand just does what it has always done.
Next time you fill up in Springfield: avoiding petrol in a diesel
- The label is what counts, and so read the petrol pump rather than the colour: in the UK unleaded handles are usually green and diesel black, but not on each forecourt.
- Plenty of cars state the fuel type inside your filler flap or on the cap, so check there on the first fill in any vehicle you don't know.
- Good intentions count for less than a sticker or a fob in a vivid colour on your diesel's key when a house has one of each. So label it.
- Before the nozzle leaves the pump the first time you fuel a hired or new motor, say "diesel" out loud. Silly, perhaps, yet it works.
- Thinking about something else is when this becomes an easy mistake to make, so put your phone away and keep your mind on the petrol pump.
- Some diesels have a filler designed to refuse 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 checking the petrol pump.
- Stop as soon as you realise. Less petrol in your tank makes a weaker mix. It does not change what to do next, which is still not to start it.
Petrol already in a diesel around Springfield? Begin here
Short and simple, then, is the order of things. Don't turn your ignition on, and don't start it. Still at the forecourt, at Esso or anywhere else? Ask the staff to help you roll it away from the pump. What got in, roughly how much, and whether it has run: tell us that when you call 0333 366 0103.
Corrosion and deposits form the problem with AdBlue, where petrol brings lost lubrication. So if it was AdBlue, say so — and read its own Springfield page.
Why one petrol in a diesel task in Springfield costs more than another
Four separate tasks lie behind the four situations above — which is why there is no honest single quote. The scenario itself does most of the work of moving the cost. Two things come after that: the petrol that went in as a share of what your tank holds, then the spot the car is in and whether a van can reach it safely.
What was put in, how much, and if it has run — three questions we ask before quoting, not after, for precisely that reason. Those answers are what turn a range into one firm number.
About Springfield itself
Springfield is a suburban area located on the outskirts of Milton Keynes in Buckinghamshire, sitting at an elevation of 92 metres near the River Great Ouse. Springfield is characterized by its terraced housing and riverside setting, with nearby amenities including Campbell Park. Springfield is close to the centre of Milton Keynes, at a distance of approximately 0.6 miles, and is about 45 miles from London.
Springfield and Buckinghamshire: where our fuel drain cover runs
Campbell Park, Woolstone and Milton Keynes are among the spots near Springfield that the same teams work, answering petrol in diesel calls across Springfield's MK postcode area. No need to bring the car to us. Forecourts, supermarket car parks, lay-bys and your own driveway are all places where we work.
Still at the petrol pump in Springfield?
Then you're in the best position there can be. Keep the vehicle turned off, then ring.