Paradise: Petrol in a Diesel Car? How Worried to Be
Likely less than you are now — as long as nobody has started the car. "Have I ruined it?" is the first thing anyone in Paradise asks, and the truthful answer is usually no, since petrol resting in a diesel tank harms nothing till it's dragged through the fuel system — by ignition priming, by your starter, or by driving. Keep it like that: leave the motor off and ring Petrol in Diesel. Keep reading for three things: the effect petrol has inside a diesel motor, the signs of how far it has got, and the way to make sure you don't repeat it.
What petrol in a diesel does to your engine
Passing through a motor, diesel is doing two jobs at once. Lubricating comes before burning; it does both. Very fine tolerances go into the injectors and the high-pressure pump, and only the diesel flowing through stops their surfaces grinding together.
The second task petrol doesn't do at all, and the first it does poorly. It is runnier than diesel and removes the protection the system depends 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 reverse of what a diesel needs from its fuel. That's where the clattering comes from.
Seen together, they show what shape the issue takes. Not contact but movement is what does the harm. Where that petrol is only inside your tank, it's an issue of fuel, nothing more. Once the pump has been running on that petrol, a mechanical problem has begun: whatever is shed by a pump that's wearing travels downstream to the injectors with your fuel.
Four scenarios we see in Paradise: how bad is petrol in a diesel?
The best case there is: filled up, not once started. At a forecourt, and really only there, the petrol is still limited to your tank — because anywhere else the vehicle was driven to reach it. The job is emptying and flushing on the spot.
A moment's running, or just the ignition on. With the system primed, the lines and filter already hold petrol that has come from that tank. That's usually still an easy task — a drain, a flush, and the fuel filter dealt with.
Those few miles driven meant the pump labouring on fuel weakened by petrol throughout. How hard your car was driven counts as much as how far, and the work takes in that tank, the fuel lines, your filter and clean fuel through the whole circuit. On the school run to South Hill Primary School, the miles is small. Very different again: a run to St Albans, under 10 miles away, or any distance on the M1, under 3 miles from Paradise, where the motor never stopped working hard.
Driven on till it complained — knocking, smoke, a ragged idle, a soft throttle. What you are hearing is the engine signalling fuel that no longer acts like diesel. Pull up wherever you are — the verge on Wolsey Road, a lay-by, a side street — and leave it there. The drain and flush-through still go first, and they sort it out: if a car is pulled over quickly, long-term damage is very uncommon.
What Paradise people 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'll be." Nothing is removed by topping up — you are left with a bigger tank, still the same mix. Percentage is not how a diesel fuel system copes with petrol, however much that guidance presumes.
Myth: "A current diesel can cope with a bit of petrol." If anything, the opposite. Lubrication counts more on newer diesels, not less, because their fuel passes through finer parts at higher pressure.
This is the one that catches people. Myth: "If it starts and drives, there's no damage done." The motorist of a petrol engine fed diesel usually has no choice but to stop, because it will not run, and the harm stops there. While your pump wears, a diesel fed petrol normally starts, ticks over and drives away as if nothing has happened. Running is not the same as fine.
Myth: "Add some two-stroke oil and drive the vehicle home." It is an outdated fix for a distinct problem. None of what petrol diluted gets put back by it — and afterwards, your tank still contains that petrol.
Myth: "Drain your tank yourself and you're sorted." Once your engine has run, some of the petrol is no longer inside the tank: it is in the fuel filter and your lines, and it goes straight back through your pump at your next start. On top of that, petrol drained into a can by the road is genuinely risky.
How petrol ends up: petrol in a diesel
No one does it on purpose, and it's rarely carelessness. A diesel nozzle generally will not go into a petrol car, but the narrower petrol nozzle goes into the filler of a diesel nearly without resistance — so forecourts make this one error simple, and just in that direction.
Routine and the car falling out of step is how it takes place. A car that is new to you — a hire car, on loan as a courtesy car, or just bought. One petrol and one diesel on the drive of the same household. The pumps in a different order on a well-known forecourt. Fuelling up in a rush on the way to Hemel Hempstead, with a train to catch. A new-to-you diesel Renault Clio, its first fuelling, and a driver accustomed to petrol: exactly when it happens. With rain, a call coming in, or a car full of children to deal with, the hand just does what it has always done.
How to avoid petrol in a diesel at your next fill-up around Paradise
- Not every forecourt in the UK keeps to green for unleaded and black for diesel, even if most usually do. Read the petrol pump's label; the colour is just a hint.
- Plenty of cars state the fuel type inside your filler flap or on the cap, so check there on your first fill in a vehicle you do not know.
- A coloured fob or a sticker on the diesel's key does more than any amount of intending to remember, for a house with one of each.
- Before the nozzle comes off the petrol pump the first time you fuel a hired or new vehicle, say "diesel" out loud. Silly, perhaps, yet it works.
- Put the phone away. This is an easy mistake to make whilst you're thinking about something else.
- A misfuel inhibitor helps, up to a point. Some diesels have a filler built to refuse a petrol nozzle, and add-on devices are available for cars without one. They are a safety net, not a reason to stop checking the pump.
- Stop as soon as you notice. Less petrol in your tank means a thinner mix. It doesn't change what to do next, which is still not to fire it up.
Already put petrol in a diesel in Paradise?
Then the order of things is brief. Do not crank it, and do not turn your ignition on. The staff on the forecourt — whether at Tesco itself or wherever you filled up — will normally help roll it clear of the petrol pump if you ask. What went in, roughly how much, and if it has run: tell us that when you call 0333 366 0103.
Say so if it was AdBlue instead of petrol: it is a separate fault, with its own page for Paradise, since AdBlue brings corrosion and deposits rather than lost lubrication.
Paradise petrol in a diesel jobs: why one costs more than another
There's no honest single quote for this, since the four scenarios above are four different jobs. What moves the cost is chiefly which of them you are in. Where your car is counts too, and whether a van can safely reach it, after the ratio of petrol to what your tank takes.
That's why our engineers ask three queries before quoting rather than after: what got in, how much, and whether it's run. A range turns into a straight figure when the replies are in.
About Paradise, briefly
Paradise is a suburban area in Hertfordshire, situated on the riverside at an elevation of 91 metres, with a mix of residential and local amenities. Paradise lies approximately 22 miles northwest of London and 6 miles southeast of St Albans, near the neighbouring areas of Hemel Hempstead and Boxmoor. Paradise is predominantly composed of flat dwellings, housing a population of around 7161 residents.
Fuel drain cover across Hertfordshire, Paradise included
Paradise sits in the HP postcode area, and the teams that answer petrol in diesel jobs there work the places around it as well — Hemel Hempstead, Corner Hall and Boxmoor among them. Our engineers drain where the car is — your own drive, a lay-by, a supermarket car park, a forecourt — so it never needs to come to us.
Still at the pump around Paradise?
The best spot there is, then — that's where you are. Switched off it remains; then phone.