Should You Worry? Petrol in a Diesel Car in Smallfield
If it has not been started, you can worry less than you likely are. Petrol resting in a diesel tank does nothing to the motor until something draws it through the system — your ignition priming the pump, your starter, or the drive on its own. So the truthful answer to the first question everyone in Smallfield asks, "have I wrecked it?", is normally no. Petrol in Diesel is who to call, with your engine kept off, so it stays that way. Further down, this page sets out what petrol really does inside a diesel, how far it might have got, and how to stop it happening to you a second time.
Petrol in a diesel: what does it do to the motor?
Two tasks fall to diesel on its journey round a motor. Oiling comes before burning; it does both. The high-pressure fuel pump and the fuel injectors are built to extremely fine clearances, and your diesel passing through them is what keeps those surfaces from grinding against each other.
The second task petrol does not do at all, and the first it does poorly. It is thinner than diesel and removes the protection the system rests on, and 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 opposite of what a diesel needs from its fuel. That's where the knocking comes from.
Combined, those leave the shape of the issue plain. The harm is done by movement, not by contact. Any tank with petrol in it is a fuel problem. A pump that has been labouring on that petrol is the start of a mechanical one, and whatever a worn pump sheds travels on with your fuel to the fuel injectors downstream.
Smallfield, petrol in a diesel: four situations, from mild to significant
Fuelled, and not started: no case is better. Being at a forecourt is what makes this possible: elsewhere, the vehicle has been driven there to begin with. With that petrol held inside that tank alone, it is drained and cleaned right where it stands, and nothing more is needed.
Ignition on, or started for a second. Once primed, the fuel system has pulled petrol out of the tank up to the filter and the fuel lines. Normally little more than clearing, rinsing and sorting the fuel filter, so still straightforward.
Those few miles driven were the pump labouring on fuel thinned by petrol throughout. How hard the vehicle was driven counts as much as how far, and the work takes in your tank, the fuel lines, the filter and clean fuel through the whole circuit. On the school run to Burstow Primary School, the distance is short. Any mileage on the M23, under a mile from Smallfield, means the engine working hard throughout, and a run to Westminster, under 25 miles away, is a very different task too.
Knocking, an uneven idle, smoke, a throttle gone soft: driven until it complained. What you are hearing is the motor signalling fuel that no longer behaves like diesel. Stop where you are — on the verge on Redehall Road, at the kerb, down a side road — and do not move it. Lasting damage is very uncommon when a vehicle is pulled over early, and the drain and flush-through that still go first take care of it.
Myths Smallfield motorists hear about petrol in a diesel
"Top it up the rest of the way with diesel and it'll be fine" — a myth. It won't. A bigger tank of the same mix is all you get, since topping up takes out nothing. The idea behind that guidance — that diesel fuel systems accept petrol by percentage — is wrong.
If anything, the opposite holds. Myth: "A newer diesel can cope with a bit of petrol." More precise parts and higher pressure are the way a newer diesel runs its fuel, and that makes the lubrication count more, not less.
"It starts, it drives, so there is no harm" — the myth that catches more people than any other. Diesel in a petrol motor normally leaves a motor that will not run: the driver stops, and so does the harm. While your pump grinds, a diesel fed petrol usually starts, ticks over and drives away as if nothing has happened. Being able to run isn't proof of being fine.
Myth: "Add some two-stroke oil and drive it home." It's an outdated workaround for a separate problem. It doesn't put back what petrol has weakened, and that petrol is still inside your tank later on.
"Drain it yourself and you're sorted" — a myth, because after it has been running some petrol lies in the fuel filter and lines, ready to go right back through the pump on the next start. Emptying petrol into a can by the kerbside is also really dangerous.
How petrol ends up: petrol in a diesel
Carelessness is seldom the cause, and nobody means to do it. The petrol nozzle is the smaller of the two and slips into a diesel filler with almost no resistance; a diesel nozzle mostly will not go into a petrol motor at all. The forecourt makes it easy, and the error runs one way.
Habit and your car getting out of step is when it takes place. Hire cars, courtesy cars, and vehicles that are new to you. One petrol and one diesel on the drive of the same household. Your normal forecourt, its pumps suddenly in a different order. A train to catch, and a rushed fill en route to Horley. Years of petrol cars behind you, a diesel Volkswagen Passat in front of you on the forecourt for its first tank — that's when. Your hand repeats what it has always done once you add rain, a phone call or a back seat full of kids.
Preventing petrol in a diesel next time you fill up in Smallfield
- The label is what counts, and so read the petrol pump instead of the colour: in the UK unleaded handles are normally green and diesel black, but not on each forecourt.
- Many cars state the fuel type inside the filler flap or on the cap, so check there on the first fill in a car you do not know.
- Label your key. In a house with one of each, a coloured fob or a sticker on the diesel's key does more than any amount of intending to remember.
- Before the nozzle leaves the petrol pump the first time you fill a hired or new car, say "diesel" out loud. Silly, yes, but it does the trick.
- 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.
- Add-on devices are available for cars without one, and some diesels are built with a filler that will not accept a petrol nozzle. Useful — but a safety net at best, never a reason to stop checking the label.
- Less petrol makes a weaker mixture, and so stop as soon as you notice — though remembering that your next stage is unchanged. It is still not to start the car.
Petrol already in a diesel in Smallfield? Start here
The order of things is brief, then. Do not fire it up, and do not turn the ignition on. Yet on the forecourt, at BP or anywhere else? Ask the staff to help you roll the car away from the pump. Next, 0333 366 0103. We will ask what was put in, about how much, and if it's been run.
If it was AdBlue instead of petrol, say so. That's a separate problem — corrosion and deposits rather than lost protection — and it has its own page for Smallfield.
One petrol in a diesel job around Smallfield costs more than another. Why?
Four different jobs lie behind the four situations above — which is why there is no fair single quote. Which of them you're in is mostly what shifts your cost. The proportion matters next, meaning how much of that tank is petrol, and then the location of the car and whether getting to it is safe for a technician.
That is why our technicians ask three questions before pricing instead of after: what got in, how much, and if it has run. Those answers turn a range into a straight figure.
About Smallfield itself
Smallfield is a village in Surrey, situated inland at an elevation of around 60 metres, and is located approximately 23 miles south of London. Smallfield has a mix of housing types, but semi-detached homes are predominant, and the village is near other local places such as Weatherhill and Burstow. Smallfield remains a relatively small community with a population of around 2058 residents. Smallfield is also close to the nearby settlement of Keepers Corner.
Fuel drain cover in Smallfield and across Surrey
Our vans answering petrol in diesel call-outs in Smallfield, in the RH postcode area, also work the locations around it, Weatherhill, Burstow and Keepers Corner included. The car doesn't need to move to us: our engineers drain on a forecourt, in a supermarket car park, in a lay-by or on your own driveway.
Still at the petrol pump in Smallfield?
Then, you could not be in a better place. Keep it off. Ring.