Should You Worry? Petrol in a Diesel Car in Longworth
Unstarted? Then less anxious than you probably are. Petrol resting in a diesel tank does nothing to the engine until something draws it through the fuel system — the ignition priming the pump, the starter, or the drive itself. So the fair answer to the first question anyone in Longworth asks, "have I wrecked it?", is usually no. To leave it that way, ring Petrol in Diesel then leave your motor alone. What petrol really does to a diesel, how to judge how far it has gone, and how to stop it from happening again: that is the remainder of this page.
What petrol in a diesel does to the motor
Diesel does two tasks on its way through a motor. Before it ignites, it lubricates — then it burns. Very fine tolerances go into your injectors and the high-pressure fuel pump, and just your diesel flowing through stops their surfaces grinding together.
The second job petrol doesn't do at all, and the first it does poorly. Being less viscous than diesel, petrol strips out the protection a fuel system needs, so a pump on that mixture wearing itself. It's equally made to resist igniting under compression — the opposite of what a diesel needs — which is why you hear the rattling.
Put these together and the shape of the issue is clear. It is circulation that causes the harm, not contact. Where the petrol is only in that tank, it is an issue of fuel, nothing more. A pump that has been working on that petrol is the start of a mechanical one, and whatever a worn pump sheds travels on with the fuel to the injectors downstream.
How serious is petrol in a diesel? Four scenarios our engineers see around Longworth
Filled but never started — as good as it gets. Being on a forecourt is what makes this possible: elsewhere, the vehicle has been driven there to begin with. With the petrol kept inside your tank alone, it's emptied and flushed on the spot, and nothing more is needed.
Ignition on, or started for a moment. The fuel system has been bled, and so petrol has left that tank and reached the filter and the lines. Still normally simple: drain, flush, and the fuel filter seen to.
Those few miles on the road meant your pump working on fuel thinned by petrol the whole way. How hard your car was driven counts as much as how far, and the work takes in the tank, the lines, the fuel filter and fresh fuel through the whole circuit. Driving the children to Longworth Primary School is one kind of trip. A run as far as Oxford, under 10 miles away, is a very different job. So is any miles on the Wheatley Spur, under 15 miles from Longworth, where the engine has been labouring hard the whole time.
Clattering, a ragged 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 Cow Lane, at the kerb, down a side road — and do not move it again. The fuel drain and flush-through still come first, and they sort it out: if a car is pulled over quickly, long-term damage is very unusual.
Stories Longworth people hear about petrol in a diesel
"Top it up the rest of the way with diesel and it will be fine" — a myth. It won't. Nothing is removed by topping up — you're left with a bigger tank, still the same mixture. A diesel fuel system does not tolerate petrol by percentage in the way that guidance supposes.
Myth: a current diesel copes with a bit of petrol. If anything, the opposite. At higher pressure, through smaller parts: that's how a current diesel handles its fuel, and so the protection counts for more, not less.
One myth that catches drivers out: if it starts and drives, it must be unharmed. The driver of a petrol engine fed diesel usually stops, because it will not run, and the harm stops with them. A diesel fed petrol usually starts, ticks over and drives away as though nothing has happened, whilst your pump grinds. Running is not the same as fine.
Myth: "Add some two-stroke oil and drive it home." It is an old fix for a separate fault. It does not put back what petrol has diluted, and the petrol is still inside the tank afterwards.
Myth: "Drain that tank yourself and you are sorted." Once the motor has been run, some of the petrol is no longer inside that tank: it is in the fuel filter and the lines, and it goes right back through your pump at your next start. It's also genuinely risky to drain petrol into a can by the roadside.
Why petrol in a diesel happens so easily
On purpose? Never. Through carelessness? Rarely, if ever. The forecourt makes it easy: the petrol nozzle is the smaller of the two, and it slips into a diesel filler with almost no resistance, while a diesel nozzle generally will not go into a petrol vehicle at all. So the mistake runs one way.
It occurs when habit and the car stop matching. A new motor, a hire car or a courtesy car. Two vehicles on one driveway, one petrol, one diesel. A forecourt you know, only with its pumps arranged differently. A rushed fill en route to Oxford with a train to catch. A new-to-you diesel Renault Megane, its first fuelling, and a driver accustomed to petrol: exactly when it takes place. Throw in a back seat full of kids, a phone call or rain, and the hand takes over.
Next time you fill up around Longworth: preventing petrol in a diesel
- Check the pump, not the colour. In the UK unleaded handles are usually green and diesel black, yet not on every forecourt. The label is what counts.
- Check the filler flap. Many motors state the fuel inside the flap or on the cap. Look at it on the first fill in any car you do not know.
- Good intentions do less than a sticker or a fob in a bright colour on the diesel's key if a household has one of each. So label it.
- It seems daft and it works: on the first fill in a new or hired car, say "diesel" out loud before you take the nozzle off the pump.
- Put the phone away. This is an easy mistake to make while you're thinking about something else.
- Some diesels have a filler built to block a petrol nozzle, and devices you can add are available for motors without one. Such an inhibitor helps up to a point — as a safety net, not a reason to stop checking the pump.
- Less petrol makes a thinner blend, so stop as soon as you notice — while remembering that the next step is unchanged. It's still not to crank it.
Already put petrol in a diesel around Longworth?
Then, there is only a short order of things. Do not crank it, and don't switch the ignition on. Ask the staff to help you roll it away from the pump if you're still on the forecourt, whether that's Pace or anywhere else. What got in, roughly how much, and whether it has run: tell us those when you ring 0333 366 0103.
Say so if it was AdBlue instead of petrol: it's a different fault, with its own page for Longworth, because AdBlue brings corrosion and deposits instead of lost protection.
What makes one Longworth petrol in a diesel job cost more than the next
The four situations above are four separate jobs, so no single price for this would be fair. Mostly, the cost shifts with which one you're in. Beyond that it is the proportion — how much petrol was put in against how much that tank holds — and after that where the car is and whether a technician can get to it safely.
That's why our engineers ask three questions before costing instead of after: what got in, how much, and whether it has run. Those replies are what turn a range into one firm number.
About Longworth, for a moment
Longworth is a small village in Oxfordshire, situated approximately 8.8 miles west of Oxford and 57.6 miles from London. Longworth sits in a rural area at an elevation of around 93 metres, surrounded by nearby villages such as Hinton Waldrist and Southmoor. Longworth has a population of around 542 people and is characterised by predominantly detached housing.
Fuel drain cover across Oxfordshire, Longworth included
Hinton Waldrist, Southmoor and Kingston Bagpuize are among the locations around Longworth that the same vans work, answering petrol in diesel jobs across Longworth's OX postcode area. A forecourt, a supermarket car park, a lay-by or your own driveway are all places our engineers drain, and your vehicle does not need to move to us.
At the pump around Longworth, right now?
The best spot there is, then — that's where you are. Phone, and keep it turned off.