Should You Worry? Petrol in a Diesel Car in North End
If it hasn't been started, you can worry less than you probably are. "Have I ruined it?" is the first thing anyone around North End asks, and the truthful answer is normally no, because petrol left in a diesel tank hurts nothing until it is drawn through the fuel system — by ignition priming, by the starter, or by being driven. Petrol in Diesel is who to call, with your engine left off, so it stays that way. The remainder of this page explains what petrol actually does to a diesel, how to judge how far it has got, and how to make sure it doesn't happen to you a second time.
What petrol in a diesel does to the motor
On its way through an engine, diesel does two tasks. Before it burns, it protects — and then it burns. What stops the surfaces inside the high-pressure fuel pump and the injectors from wearing against each other is your diesel passing through them — they are designed to extremely fine gaps.
Poorly at the first, not at all at the second: that's petrol. The rattling comes from petrol being made not to ignite when compressed, which is exactly the reverse of what a diesel needs. On top of that it is thinner than diesel, it strips out the protection your system hinges on, and any pump working on that mixture is wearing itself.
Put these together and the shape of the issue is plain. Contact doesn't do the harm — movement does. Where that petrol is only inside your tank, it's a problem of fuel, nothing more. Whatever a worn pump sheds travels on, carried by the fuel, into the fuel injectors further along, which is why a pump that has worked on that petrol is where a mechanical problem begins.
Four scenarios we see in North End: how bad is petrol in a diesel?
Fuelled but never started — as good as it gets. Just your tank has petrol in it, and so the job is emptying your tank and flushing the system where the vehicle sits. This situation can only truly take place at a forecourt: anywhere else, the vehicle got there by being driven.
Ignition on, or started for a second. Petrol has left that tank and got to the fuel filter and your lines, because the fuel system has been primed. That is generally still a simple job — a drain, a flush, and the fuel filter seen to.
Those few miles on the road were the pump labouring on fuel thinned by petrol throughout. How hard your car was driven matters as much as how far, and the work takes in the tank, your lines, the fuel filter and clean fuel through the whole system. A school run to St Michael's Church of England Combined School is one thing. A run as far as Milton Keynes, under 10 miles away, is a very different task. So is any mileage on the M1, under 10 miles from North End, where the engine has been working hard throughout.
Knocking, an uneven idle, smoke, a throttle gone soft: driven till it complained. The fuel is not behaving like diesel any more, and your motor is saying so. Whether it is the verge on High Street North, a lay-by or a side road, stop where you are then leave it. A car pulled over soon very seldom has lasting damage, as the fuel drain and the flush-through, which still come first, deal with it.
What North End motorists get told about petrol in a diesel — and the myths in it
It will not be fine. The myth: "Fill it the rest of the way with diesel and it will be." Nothing comes out when you top up — your tank just carries more of the same blend. The idea behind the guidance — that diesel fuel systems accept petrol by percentage — is wrong.
Myth: "A modern diesel can cope with a bit of petrol." If anything, the opposite. At higher pressure, through finer parts: that is how a modern diesel moves its fuel, and so the lubrication counts for more, not less.
Myth: "If it starts and drives, there is no damage done." This is the one that catches people. Diesel in a petrol motor generally leaves a motor that will not run: the motorist stops, and so does the damage. Nothing seems to have happened when a diesel fed petrol fires up, ticks over and drives away, as it usually does; meanwhile your pump wears. Running does not mean fine.
"A drop of two-stroke oil and drive it home" — a myth, borrowed from a fix from years ago, for a different fault. None of what petrol weakened gets put back by it — and later, your tank still contains the petrol.
"Drain it yourself and you are sorted" — a myth, since after it's been running some petrol sits in your filter and lines, ready to go right back through your pump at your next start. It is also genuinely risky to drain petrol into a can at the roadside.
How petrol ends up: petrol in a diesel
A careless moment is rarely the cause, and nobody means to do it. The petrol nozzle is the slimmer of the two and slips into a diesel filler with almost no resistance; a diesel nozzle generally will not go into a petrol car at all. The forecourt makes it simple, and the slip runs one way.
Habit and your car getting out of step is when it occurs. Hire cars, courtesy cars, and motors that are new to you. Households running one of each, petrol and diesel. A forecourt you know, only with its pumps laid out differently. A hurried fill on the way to Leighton Buzzard with a train to catch. A new-to-you diesel Renault Megane, its first fuelling, and a motorist accustomed to petrol: precisely when it takes place. With rain, a call coming in, or children to deal with, your hand simply does what it always has.
Preventing petrol in a diesel next time you fill up around North End
- Not every forecourt in the UK keeps to green for unleaded and black for diesel, even if most generally do. Read the petrol pump's label; the colour is just a hint.
- Inspect your filler flap. Plenty of motors state the fuel type inside the flap or on the cap. Look at it on the first fill in a motor you do not know.
- A coloured fob or a sticker on your diesel's key does more than any amount of meaning to remember, for a home with one of each.
- It seems silly and it does the trick: on your first fill in a new or hired car, say "diesel" aloud before you lift the nozzle off the petrol pump.
- Thinking about something else is when this becomes an easy mistake to make, and so put your phone away then keep your mind on the petrol pump.
- Some diesels come with a filler designed to reject a petrol nozzle, and devices you can add exist for cars without one. Such an inhibitor helps up to a point — as a backstop, not a reason to stop reading the pump.
- Spotting it mid-fill? Stop there and then. A weaker blend results from less petrol inside that tank, but your next step remains the same: don't fire it up.
North End: already put petrol in a diesel?
Then the order of things is short. Never fire it up, and don't switch the ignition on. Yet on the forecourt, at Texaco or anywhere else? Ask the staff to help you roll the vehicle clear of the petrol pump. What went in, about how much, and if it has run: tell us those when you phone 0333 366 0103.
Say so if it was AdBlue instead of petrol: it's a different fault, with its own page for North End, because AdBlue brings corrosion and deposits rather than lost protection.
One petrol in a diesel task in North End costs more than another. Why?
Four separate tasks lie behind the four scenarios above — which is why there's no fair single price. Chiefly, the cost moves with which one you're in. Next it is the ratio — how much petrol was put in against how much that tank holds — and then where the vehicle is and whether our van can get to it safely.
Three queries come first, before any quote, instead of after — what got in, how much, has it run — and that is the reason. A range becomes a straight figure once those answers are in.
About North End itself
North End is a suburban area in Buckinghamshire, situated approximately 7.6 miles from Milton Keynes and 40.3 miles northwest of London. North End sits in a rural setting at an elevation of around 149 metres, with nearby villages including Stewkley and Stewkley Dean. North End is characterized by its predominantly detached housing stock, reflecting its development as a residential area. North End remains a small community with a population of around 696 residents.
Across Buckinghamshire and around North End: fuel drain cover
Stewkley, Stewkley Dean and South End are among the locations near North End that the same teams work, answering petrol in diesel calls across North End's LU postcode area. No need to bring the vehicle to us. Forecourts, supermarket car parks, lay-bys and your own drive are all locations we drain.
North End: still at the pump?
No position is better: that is where you now are. Leave the vehicle turned off, then ring.