Petrol in a Diesel Car in Penn: How Worried Should You Be?
Probably less than you are now — as long as nobody has started it. Till the ignition primes the pump, your starter cranks, or the vehicle is driven, petrol in a diesel tank just sits there and does no harm. Which means the honest reply to the first Penn question — "have I ruined it?" — normally no. To leave the car like that, ring Petrol in Diesel then leave the motor switched off. Read on for three things: the effect petrol has inside a diesel motor, the clues of how far it has spread, and the way to make sure you never repeat it.
Petrol in a diesel: what does it do to your engine?
Two jobs fall to diesel on its journey round a motor. Before it ignites, it lubricates — then it burns. The high-pressure fuel pump and the injectors are designed to extremely fine clearances, and your diesel passing through them is what keeps those surfaces from grinding against each other.
Poorly at the first, not at all at the second: that's petrol. A pump working on a petrol blend is wearing itself out, since petrol is runnier than diesel and strips out the lubrication the fuel system relies on. Petrol is also made to resist igniting under compression — the opposite of what a diesel wants from its fuel — and that is where the rattling comes.
Combined, those make the shape of the problem plain. It is movement that does the damage, not contact. All a tank with petrol in it amounts to is a fuel problem. A pump that has been working on that petrol is the beginning of a mechanical one, and whatever a worn pump sheds moves on with your fuel to your injectors downstream.
Petrol in a diesel in Penn: how bad is it? Four situations
Filled up, and never started: no case is better. At a forecourt, and genuinely only there, the petrol is still confined to that tank — since everywhere else the vehicle was driven to get to it. The task is emptying and rinsing on the spot.
Started for a moment, or just the ignition on. The system has been primed, and so petrol has left your tank and got to your filter and the fuel lines. Drain, flush, deal with the fuel filter: still normally straightforward.
The pump now worked a couple of miles on weakened fuel — that is what driving it does. Tank, lines, filter, then clean fuel run through the entire circuit: that is the work, and the way the car was driven counts as much as the miles. On the school run to Tylers Green First School, the miles is small. A run as far as St Albans, under 25 miles away, is a very different job. So is any miles on the M40, under 3 miles from Penn, where the motor has been working hard the whole time.
Driven till it complained. Knocking, a lumpy idle, smoke, a throttle that has gone soft. The motor is telling you the fuel is no longer behaving like diesel. Whether it's the verge on Hammersley Lane, a lay-by or a side street, stop where you are and leave it. Lasting damage is very unusual if a vehicle is stopped early, and the fuel drain and flush-through that still come first deal with it.
What Penn motorists get told about petrol in a diesel — and the stories in it
It will not be fine. The myth: "Fill it the rest of the way with diesel and it will be." Nothing is removed by topping up — you're left with a bigger tank, still the same mix. Percentage is not how a diesel fuel system copes with petrol, whatever that guidance presumes.
Not so: a modern diesel copes with a bit of petrol. If anything, the reverse. A modern diesel runs its fuel through finer parts at higher pressure, which makes the protection count more, not less.
Myth: "If it starts and drives, there is no harm done." This is the one that catches people. Feed diesel to a petrol motor and it normally won't run, so the driver stops — and the harm stops with them. A diesel fed petrol usually starts, idles and drives away as though nothing has happened, while your pump wears. Being able to run isn't the same as being fine.
An outdated workaround for a different problem lies behind this one. Myth: "Add some two-stroke oil and drive the vehicle home." What petrol has thinned stays diluted, and that petrol remains inside that tank anyway.
Myth: "Drain the tank yourself and you are sorted." After the motor has been run, some of the petrol is no longer in your tank: it is in the fuel filter and the lines, and it goes right back through your pump at the next start. It's also truly hazardous to drain petrol into a can by the kerbside.
How does petrol in a diesel take place?
No one does it on purpose, and it's seldom carelessness. A diesel nozzle mostly won't go into a petrol car, yet the smaller petrol nozzle goes into the filler of a diesel nearly without resistance — so forecourts make this one error straightforward, and just in one direction.
When routine and your car stop matching, it happens. Hire cars, courtesy cars, and motors that are new to you. Two cars on one drive, one petrol, one diesel. A well-known forecourt with the pumps in a different order. Filling up in a rush en route to High Wycombe, with a train to catch. Years of petrol vehicles behind you, a diesel Renault Megane in front of you on the forecourt for its first tank — that's when. Add rain, a phone call or a back seat full of children, and the hand does what it has always done.
Preventing petrol in a diesel next time you fill up in Penn
- Not every forecourt in the UK keeps to green for unleaded and black for diesel, though most generally do. Check the pump's label; the colour is only a clue.
- Plenty of motors state the fuel type inside the filler flap or on the cap, so check there on your first fill in any car you don't know.
- One of each in the home? Label your key to your diesel — a coloured fob, a sticker — because meaning to remember is not enough.
- It sounds daft and it works: on your first fill in a new or hired car, say "diesel" out loud before you lift the nozzle off the petrol pump.
- While you're thinking about something else, this is an easy mistake to make — so tuck the phone away.
- Up to a point, a misfuel inhibitor helps: some diesels have a filler designed to refuse a petrol nozzle, and aftermarket devices are available for the rest. Count it as a backstop, and keep checking the petrol pump.
- Less petrol makes a weaker mixture, and so stop the moment you notice — while remembering that the next stage is unchanged. It is still not to crank it.
Petrol already in a diesel around Penn? Start here
The order of things is short, then. Starting it is out, and so is switching on your ignition. Ask the staff to help you roll it away from the pump if you're still at the forecourt, whether that's JET or somewhere else. Next, 0333 366 0103. We'll ask what was put in, about how much, and if it has been run.
If it was AdBlue and not petrol, say so. That's a separate issue — corrosion and deposits instead of lost lubrication — and it has its own page for Penn.
What makes one Penn petrol in a diesel job cost more than the next
A fair single price does not exist here: four scenarios, four separate tasks. What shifts the cost is chiefly which of them you are in. Where the vehicle is counts too, and whether a technician can safely reach it, after the share of petrol to what that tank holds.
Three queries come first, before any quote, rather than after — what got in, how much, has it run — and that is the reason. Those replies change a range into a straight figure.
About Penn
Penn is a village in Buckinghamshire, situated in the Chiltern Hills at an elevation of 163 metres. Penn lies approximately 25.9 miles west of London and 17.3 miles southwest of St Albans, near the villages of Tylers Green, Micklefield, and Hazlemere. Penn has a population of around 1773 residents, predominantly living in detached houses.
Fuel drain cover around Penn and across Buckinghamshire
Penn sits in the HP postcode area, and the vans that answer petrol in diesel jobs there work the locations around it as well — Tylers Green, Micklefield and Hazlemere among them. No need to move the vehicle to us. Forecourts, supermarket car parks, lay-bys and your own driveway are all places we drain.
At the pump in Penn, right now?
No position is better: that's where you are. Keep it off. Ring.