Poundfield: Petrol in a Diesel Car? How Worried to Be
If it has not been started, worry far less than you likely are. Until the ignition primes the pump, the starter turns, or the vehicle is driven, petrol in a diesel tank just sits there and does no harm. Which means the honest reply to that first Poundfield question — "have I wrecked it?" — normally no. To keep the vehicle that way, call Petrol in Diesel then leave your engine switched off. Further down, this page sets out what petrol actually does inside a diesel, how far it might have gone, and how to stop it happening to you a second time.
Inside the engine: what petrol in a diesel does
Two tasks fall to diesel on its route through a motor. It burns, and before it burns it protects. Extremely fine tolerances go into your injectors and the high-pressure fuel pump, and only your diesel flowing through stops their surfaces grinding together.
The second job petrol doesn't do at all, and the first it does poorly. It is thinner than diesel and takes away the lubrication the system depends on, so a pump running on a petrol mixture is a pump wearing itself. And petrol is designed to resist igniting under compression, which is the reverse of what a diesel needs from its fuel. That is where the knocking comes from.
Together, those make the shape of the problem clear. It is circulation that causes the damage, not contact. Any tank with petrol in it is a fuel fault. The beginning of a mechanical problem is a pump that has been labouring on that petrol — and whatever a worn pump sheds travels on with the fuel to the fuel injectors beyond it.
Four scenarios our technicians see around Poundfield: how serious is petrol in a diesel?
The best case there is: filled up, not once started. Being at a forecourt is what makes this possible: elsewhere, the vehicle has been driven there to begin with. With that petrol kept in the tank alone, it is cleared and rinsed right where it stands, and nothing more is needed.
Ignition on, or started for a second. With the fuel system primed, the lines and filter already contain petrol that has come from your tank. That's generally still a simple job — a drain, a flush, and your filter seen to.
The pump now worked a few miles on weakened fuel — that's what driving the car meant. Miles is only half of that; how hard it was driven matters just as much. Either way the work runs to your tank, your lines, your filter and clean fuel through the entire circuit. Short trips, such as the school run to Sir Henry Fermor Church of England Primary School, are one thing. Any miles on the M23, under 15 miles from Poundfield, means your engine has worked hard throughout, and a run to Brighton and Hove, under 25 miles away, makes a very different task too.
Driven until it protested. Clattering, a lumpy idle, smoke, a throttle that has gone soft. That is the motor telling you its fuel no longer is behaving like diesel. Stop wherever you are — the verge on Pellings Farm Close, a lay-by, a side street — then leave the car there. A car pulled over soon very rarely has permanent damage, as the drain and the flush-through, which still come first, take care of it.
Myths Poundfield people 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're left with a fuller tank, still the same mix. A diesel fuel system doesn't accept petrol by percentage in the way that advice supposes.
Myth: "A current diesel can cope with a bit of petrol." If anything, the reverse. Protection matters more on current diesels, not less, since their fuel passes through smaller parts at higher pressure.
Myth: "If it starts and drives, there's no damage done." This is the one that catches drivers. The driver of a petrol engine fed diesel normally stops, because it will not run, and the harm stops there. A diesel fed petrol normally starts, ticks over and drives away as if nothing has happened, while your pump wears. Fine and running aren't the same at all.
Myth: "Add some two-stroke oil and drive the car home." It is an outdated workaround for a different fault. What petrol has weakened stays diluted, and the petrol stays inside that tank regardless.
The next start sends petrol back round your pump out of the fuel lines and your filter, where some of it ends up once the motor has been run. That is why a DIY tank drain doesn't sort it — a myth. On top of that, petrol cleared into a can by the road is genuinely risky.
How does petrol in a diesel take place?
Nobody does it on purpose, and it's seldom carelessness. One way only, since of the nozzles: the slimmer petrol one slips inside a diesel filler with almost no resistance, whereas the diesel one generally won't fit a petrol car. That is how the forecourt makes it straightforward.
When habit and your car stop matching, it occurs. A motor that is new to you — hired, on loan as a courtesy car, or brand new. One petrol and one diesel on the driveway of the same household. A familiar forecourt with the pumps in a different order. Fuelling up in a rush on the way to Crowborough, 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. Your hand repeats what it has always done when you add rain, a phone call or a back seat full of children.
Avoiding petrol in a diesel next time you fill up in Poundfield
- A green handle for unleaded and black for diesel is normal in the UK — yet not on every forecourt. Trust the label on the petrol pump, not the colour.
- Inspect your filler flap. Plenty of motors state the fuel type inside the flap or on the cap. Look at it on your first fill in any car you don't know.
- One of each in the house? Label your key to the diesel — a coloured fob, a sticker — since intending to remember isn't enough.
- Say it before you lift it. On your first fill in a new or hired car, say "diesel" out loud before you lift the nozzle off the petrol pump. It seems daft and it works.
- Mistakes like this are simple to make whilst your mind is on something else, so your phone goes away.
- Up to a point, a misfuel inhibitor helps: some diesels come with a filler built to reject a petrol nozzle, and add-on devices exist for the rest. Count it as a backstop, and keep checking the petrol pump.
- Stop as soon as you notice. Less petrol inside the tank means a weaker mix. It does not change what to do next, which is still not to start the vehicle.
Petrol already in a diesel around Poundfield? Start here
Then the order of things is brief. Don't switch the ignition on, and do not crank it. Ask the staff to help you roll it away from the pump if you are still on the forecourt, whether that's Esso or anywhere else. What went in, about how much, and whether it's run: tell us that when you call 0333 366 0103.
If it was AdBlue and not petrol, say so. That's a separate fault — corrosion and deposits and not lost protection — and it has its own page for Poundfield.
One petrol in a diesel job around Poundfield costs more than another. Why?
There's no fair single price for this, since the four situations above are four separate jobs. Which of them you are in is mostly what moves the cost. Two things come after that: the petrol that went in as a share of what your tank holds, then the place your car is in and whether a van can get to it safely.
What was put in, how much, and whether it has run — three questions we ask before costing, not after, for precisely that reason. Those replies change a range into a straight figure.
About Poundfield and where it is
Poundfield is a suburban area situated near the River Uck in East Sussex, with a mix of detached housing and rural surroundings. Poundfield sits at an elevation of around 160 metres, overlooking the rolling countryside of the South East. Poundfield is located near several smaller settlements, including Steel Cross and Blackness, and is within commuting distance of Brighton and Hove. Poundfield has a population of approximately 2964 residents, living in predominantly detached homes.
Across East Sussex and around Poundfield: fuel drain cover
Petrol in diesel call-outs in Poundfield — part of the TN postcode area — go to teams that likewise cover the places round it, Steel Cross, Blackness and Crowborough included. You need not bring the vehicle to us. Forecourts, supermarket car parks, lay-bys and your own drive are all places we drain.
Still at the petrol pump in Poundfield?
Then you're in the best place there is. Leave the car turned off, and ring.