Great Dunmow: Petrol in a Diesel Car? How Worried to Be
Unstarted? Then less worried than you likely are. Petrol resting in a diesel tank does nothing to your engine till something draws it through the fuel system — your ignition priming the pump, the starter, or driving on its own. So the truthful answer to the first question everyone around Great Dunmow asks, "have I wrecked it?", is generally no. To leave the vehicle like that, ring Petrol in Diesel then leave your engine alone. What petrol actually does to a diesel, how to gauge how far it's travelled, and how to stop it from happening again: that is the rest of this page.
The motor and petrol in a diesel: what happens
Diesel does two jobs on its way through an engine. It burns, and before it burns it protects. Very fine gaps are built into the injectors and your high-pressure pump, and only the diesel running through keeps those surfaces from grinding together.
Petrol does the first task poorly and the second not at all. The clattering comes from petrol being designed not to ignite when compressed, which is precisely the reverse of what a diesel needs. On top of that it is thinner than diesel, it strips away the protection the system rests on, and any pump working on such a blend is wearing itself.
Together, those leave the shape of the problem clear. The harm is done by circulation, not by contact. A tank with petrol in it is a fuel problem. A pump that has been running on that petrol is the beginning of a mechanical one, and whatever a worn pump sheds moves on with your fuel to the fuel injectors downstream.
How bad is petrol in a diesel? Four scenarios our engineers see in Great Dunmow
Filled but not once started — as good as it gets. Just that tank has petrol in it, so the task is clearing that tank and flushing the fuel system where the vehicle stands. This scenario can only truly take place at a forecourt: anywhere else, the car got there by being driven.
The ignition turned on, or a brief start. With the fuel system primed, the fuel lines and filter already hold petrol that has come from that tank. Drain, flush, see to the fuel filter: still normally simple.
The pump has worked a few miles on thinned fuel — that is what driving the vehicle does. How hard your car was driven matters as much as how far, and the work takes in that tank, your lines, the filter and fresh fuel through the entire circuit. Short trips, such as the school run to Dunmow St Mary's Primary School, are one thing. Very different a second time: a trip to Chelmsford, under 15 miles away, or some distance on the M11, under 10 miles from Great Dunmow, where the motor never stopped working hard.
Driven till it complained. Rattling, a lumpy idle, smoke, a throttle that has gone soft. What you are hearing is your motor reporting fuel that no longer runs like diesel. Leave it wherever it stops: a lay-by, a quiet street, the verge on New Street. What goes first is still the fuel drain and flush, and that sorts it out, with lasting damage very unusual when a car is stopped early.
Petrol in a diesel stories Great Dunmow motorists hear
False: topping up to full with diesel makes it fine. It doesn't. A bigger tank of the same mixture is all it gives, since topping up removes nothing. The idea behind that advice — that diesel fuel systems accept petrol by percentage — is wrong.
Myth: "A newer diesel can cope with a bit of petrol." If anything, the opposite. Protection counts more on newer diesels, not less, because their fuel runs through smaller components at higher pressure.
This is the one that catches drivers. Myth: "If it starts and drives, there is no harm done." Diesel in a petrol motor generally leaves a motor that won't run: the motorist stops, and so does the damage. A diesel fed petrol usually starts, ticks over and drives away as though nothing has happened, whilst your pump grinds. Running isn't the same as fine.
An outdated fix for a different fault lies behind this one. Myth: "Add some two-stroke oil and drive it home." It does not put back what petrol has diluted, and that petrol is still in that tank afterwards.
The next start sends petrol back round the pump from your lines and the fuel filter, where some of it sits once your engine has been run. That is why a DIY tank drain doesn't sort it — a myth. Also, a can of petrol filled by the kerbside is genuinely hazardous.
Why petrol in a diesel happens at all
No one does it on purpose, and it is rarely carelessness. One way only, because of the nozzles: the slimmer petrol one slides inside a diesel filler with almost no resistance, whereas the diesel one generally will not fit a petrol motor. That is how the forecourt makes it easy.
When habit and the car stop matching, it happens. Hire cars, courtesy cars, and cars that are new to you. One petrol and one diesel on the driveway of the same household. A forecourt you know, but with its pumps arranged differently. Rushing for a train at Stansted Airport and fuelling up en route. Precisely the moment it happens: after years of driving petrol, a driver fills a diesel Volkswagen Passat for the first time. Add a back seat full of kids, a phone call or rain, and habit wins.
Next time you fill up around Great Dunmow: preventing petrol in a diesel
- The label is what counts, and so read the pump instead of the colour: in the UK unleaded handles are normally green and diesel black, but not on each forecourt.
- Inspect your filler flap. Plenty of vehicles state the fuel inside the flap or on the cap. Look at it on the first fill in any vehicle you don't know.
- Label your key. In a home with one of each, a coloured fob or a sticker on your diesel's key does more than any amount of meaning to remember.
- Before the nozzle leaves the petrol pump the first time you fill a hired or new car, say "diesel" out loud. Daft, yes, but it does the trick.
- Put your phone away. This is an easy mistake to make whilst you are thinking about something else.
- 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 cars without one. They are a safety net, not a reason to stop reading the petrol pump.
- Spotting it mid-fill? Stop there and then. A thinner mixture follows from less petrol in your tank, yet your next stage remains the same: don't start the car.
Already put petrol in a diesel in Great Dunmow?
Then the order of things is brief. Never fire it up, and don't switch the ignition on. Still at the forecourt, at Tesco or anywhere else? Ask the staff to help you push the car clear of the pump. Next, 0333 366 0103. We'll ask what got in, roughly how much, and if it has been run.
Say so if it was AdBlue rather than petrol: it's a separate fault, with its own page for Great Dunmow, because AdBlue brings corrosion and deposits rather than lost lubrication.
Great Dunmow petrol in a diesel jobs: why one costs more than another
Four different tasks sit behind the four scenarios above — which is why there is no fair single price. Mostly, the cost moves with which situation you're in. The share matters next, meaning how much of your tank is petrol, followed by the position of the car and whether reaching it is safe for a van.
Before any quote, not after, we ask three queries: the fuel that got in, its amount, and if it's run. That is why. A range turns into a straight figure when the replies are in.
About Great Dunmow, for a moment
Great Dunmow is a town situated in the county of Essex, on the banks of the River Chelmer at an elevation of around 75 metres. Great Dunmow has a mix of old and new housing, with detached homes being the predominant type, and is located near other small communities such as Church End and Barnston. Great Dunmow is also close to the city of Chelmsford, which is about 10 miles away, and is around 33 miles from London. Great Dunmow has a population of approximately 10,033 people.
Fuel drain cover across Essex, Great Dunmow included
Our teams answering petrol in diesel calls around Great Dunmow, in the CM postcode area, also work the locations near it, Church End, Pharisee Green and Barnston included. A forecourt, a supermarket car park, a lay-by or your own driveway are all locations we work, and the vehicle doesn't need to move to us.
At the pump in Great Dunmow, right now?
Then, you could not be in a better place. Turned off it remains; then ring.