Knocklaw: Petrol in a Diesel Car? How Worried to Be
Not started? Then less anxious than you likely feel. Petrol sitting in a diesel tank does nothing to your engine until something draws it through the fuel system — the ignition priming the pump, the starter, or the drive on its own. So the honest answer to the first question everyone around Knocklaw asks, "have I wrecked it?", is normally no. Petrol in Diesel is who to call, with the motor kept off, so it stays that way. Below, this page sets out what petrol actually 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 engine?
Passing through an engine, diesel does two jobs at once. It protects to begin with, and only then does it burn. Designed to very fine tolerances, your injectors and the pump depend on your diesel moving through them to keep their surfaces from wearing against one another.
The second job petrol doesn't do at all, and the first it does poorly. A pump running on a petrol blend is wearing itself out, because petrol is thinner than diesel and strips out the protection your fuel system relies on. Petrol is also designed to resist igniting under compression — the opposite of what a diesel needs from its fuel — and that is where any rattling starts.
Taken together, they make clear what shape the problem has. The harm is done by circulation, not by contact. Any tank with petrol in it is a fuel problem. The beginning of a mechanical problem is a pump that has been working on that petrol — and whatever a worn pump sheds travels on with the fuel to the injectors downstream.
How serious is petrol in a diesel? Four scenarios we see in Knocklaw
Fuelled but never started — the best it gets. 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's emptied and cleaned right where it stands, and nothing more is needed.
Ignition on, or started for a second. Your system has been primed, and so petrol has left your tank and got to the fuel filter and your lines. Drain, flush, see to your filter: still usually simple.
Driven a few miles. Now the pump has spent these miles working on diluted fuel. Tank, lines, filter, then clean fuel run through the whole system: that's this work, and the way the vehicle was driven counts as much as the distance. A school run to Rothbury First School is one thing. A run as far as Newcastle upon Tyne, under 50 miles away, is a very different job. So is any mileage on the A167(M), under 50 miles from Knocklaw, where the motor has been running hard throughout.
Driven on until it protested — knocking, smoke, a ragged idle, a soft throttle. The fuel is not acting like diesel any more, and your engine is telling you. Stop wherever you are — the verge on Knocklaw Park, a lay-by, a side street — and leave it where it is. A car pulled over quickly very rarely has lasting damage, since the fuel drain and the flush-through, which still come first, take care of it.
What Knocklaw drivers get told about petrol in a diesel — and the myths in it
Myth: topping up to full with diesel makes it fine. It does not. Nothing is removed when you top up — the tank simply holds more of the same mixture. Percentage is not how a diesel fuel system tolerates petrol, however much that advice supposes.
If anything, the reverse is true. Myth: "A modern diesel can cope with a bit of petrol." Finer components and higher pressure are the way a modern diesel runs its fuel, and that makes the protection count more, not less.
One myth that catches people out: if it starts and drives, it must be unharmed. Feed diesel to a petrol motor and it generally won't run, and so the driver stops — and the harm stops with them. Whilst the pump wears, a diesel fed petrol normally starts, idles and drives away as though nothing has happened. Running does not mean fine.
An old workaround for a different issue is behind this one. Myth: "Add some two-stroke oil and drive the car home." None of what petrol weakened is put back by it — and later, that tank still holds that petrol.
Once your engine has been run, part of the petrol is in your filter and the lines, not that tank — and the next start sends it right back through your pump. So the myth "drain the tank yourself and you are sorted" doesn't hold. Emptying petrol into a can by the kerbside is also really risky.
How does petrol in a diesel occur?
A careless moment is seldom the cause, and no one means to do it. A diesel nozzle mostly will not fit a petrol motor, but the slimmer petrol nozzle goes into the filler of a diesel almost without resistance — so forecourts make this one mistake simple, and only in that direction.
It occurs when routine and the vehicle stop matching. Hire cars, courtesy cars, and cars that are new to you. Households running one of each, petrol and diesel. The pumps in a different order on a familiar forecourt. A train to catch, and a hurried fill on the way to Acklington. A new-to-you diesel Volkswagen Golf, its first fuelling, and a motorist used to petrol: precisely when it occurs. With rain, a call arriving, or children to deal with, the hand simply does what it has always done.
Preventing petrol in a diesel next time you fill up in Knocklaw
- The label is what matters, and so check the pump rather than the colour: in the UK unleaded handles are usually green and diesel black, but not on every forecourt.
- Inspect the filler flap. Plenty of cars state the fuel type inside the flap or on the cap. Look at it on your first fill in a vehicle you don't know.
- One of each in the household? Mark your key to your diesel — a coloured fob, a sticker — since meaning to remember is not enough.
- "Diesel", out loud, before you lift the nozzle — each time a new or hired car needs its first tank. It sounds silly. It works.
- Thinking about something else is when this becomes an easy mistake to make, so put the phone away then keep your mind on the petrol pump.
- Add-on devices exist for vehicles without one, and some diesels come with a filler that won't take a petrol nozzle. Helpful — but a safety net only, never a reason to stop checking the label.
- As soon as you realise, stop: less petrol inside that tank makes a weaker mix. What to do next doesn't change, though — still don't fire it up.
Already put petrol in a diesel around Knocklaw?
Then the order of things is short. Leave it unstarted, with the ignition switched off as well. Still at the forecourt, at Shell or anywhere else? Ask the staff to help you roll it away from the petrol pump. Call 0333 366 0103 next, with three answers — the fuel, the approximate volume, and whether it has run.
If it was AdBlue instead of petrol, say so. That is a different fault — corrosion and deposits rather than lost lubrication — and it has its own page for Knocklaw.
Knocklaw petrol in a diesel jobs: why one costs more than another
There is no fair single price for this, since the four scenarios above are four separate tasks. Chiefly, the cost shifts with which one you are in. The share matters next, meaning how much of the tank is petrol, followed by the location of the vehicle and whether getting to it is safe for our van.
That is why our engineers ask three questions before pricing instead of after: what went in, how much, and whether it has run. With the answers, there is a straight figure rather than a range.
About Knocklaw
Knocklaw is a suburban area situated on the riverside in Northumberland, with a mix of terraced housing and a population of around 1076 residents. Knocklaw sits at an elevation of 83 metres, approximately 25.7 miles north of Newcastle upon Tyne, and is near the towns of Rothbury, Whitton, and Newtown. Knocklaw is located in a scenic part of the North East region, with the city of Newcastle upon Tyne being the nearest major urban centre.
Knocklaw and Northumberland: where our fuel drain cover runs
The vans answering petrol in diesel calls in Knocklaw, in the NE postcode area, also work the spots near it, Rothbury, Whitton and Newtown included. A forecourt, a supermarket car park, a lay-by or your own drive are all spots we work, and your car doesn't need to move to us.
Still at the petrol pump around Knocklaw?
No position is better: that is where you now are. Switched off it remains; then call.