The Crescent: Petrol in a Diesel Car? How Worried to Be
Less than you likely are, provided it has not been started. Everyone in The Crescent starts with "have I ruined it?", and the honest answer is usually no: petrol resting in your tank of a diesel stays harmless till priming, cranking or driving pulls it into the fuel system. Keep it like that: leave your motor off then call Petrol in Diesel. Keep reading for three things: the effect petrol has inside a diesel engine, the clues of how far it has got, and the way to make sure you don't do it again.
Inside the motor: what petrol in a diesel really does
Passing through an engine, diesel is doing two things at the same time. It burns, and before it ignites it protects. The high-pressure pump and the fuel injectors are made to very fine gaps, and the diesel passing through them is what stops those surfaces from grinding against each other.
Poorly at the first, not at all at the second: that's petrol. A pump running on a petrol mix is wearing itself out, because petrol is thinner than diesel and strips out the lubrication your fuel system relies on. Petrol is also made to resist igniting under compression — the reverse of what a diesel needs from its fuel — and that is where any clattering starts.
Taken together, they show what shape the issue has. The damage is done by movement, not by contact. Where the petrol is only inside your tank, it is a fault of fuel, nothing more. The start of a mechanical problem is a pump that has been working on that petrol — and whatever a worn pump sheds moves on with the fuel to your injectors beyond it.
Petrol in a diesel in The Crescent: how serious is it? Four cases
Fuelled, and not started: nothing beats it. At a forecourt, and genuinely only there, that petrol is still limited to that tank — since anywhere else your car was driven to reach it. The task is draining and flushing on the spot.
Your ignition switched on, or a short start. Petrol has come out of that tank and reached the fuel filter and the lines, because the fuel system has been primed. Still generally simple: drain, flush, and your filter dealt with.
Those few miles on the road were the pump labouring on fuel diluted by petrol throughout. The work is that tank, the lines, the fuel filter and fresh fuel through the whole circuit, and how hard the car was driven matters as much as how far. Driving the children to St Andrew's CofE (VA) Junior School is one kind of trip. A run as far as Bradford, under 10 miles away, is a very different job. So is any distance on the M62, under 3 miles from The Crescent, where the engine has been working hard throughout.
Knocking, a ragged idle, smoke, a throttle gone soft: driven until it complained. The engine is telling you the fuel is no longer acting like diesel. Leave it where it stops: a lay-by, a quiet street, the verge on Manley Street. The fuel drain and flush still come first, and they sort it out: when a car is pulled over soon, permanent damage is very unusual.
Myths The Crescent people hear about petrol in a diesel
Myth: "Fill it the rest of the way with diesel and it will be fine." It will not. Nothing comes out when you top up — the tank simply carries more of the same mixture. Percentage is not how a diesel fuel system copes with petrol, whatever that advice presumes.
If anything, the reverse is true. Myth: "A newer diesel can cope with a bit of petrol." At higher pressure, through finer components: that's how a newer diesel moves its fuel, so the lubrication matters for more, not less.
This is the one that catches motorists. Myth: "If it starts and drives, there's no damage done." Feed diesel to a petrol engine and it usually won't run, and so the driver stops — and the damage stops with them. Feed petrol to a diesel and it usually starts, ticks over and drives away like nothing has happened — all the while its pump is wearing. Running isn't the same as fine.
Myth: "Add some two-stroke oil and drive the vehicle home." It's an old fix for a different issue. It doesn't put back what petrol has diluted, and that petrol is still in your tank after that.
The next start sends petrol back round the pump out of the fuel lines and the filter, where some of that ends up once the motor has run. That's why draining your tank yourself does not leave you sorted — a myth. Also, a can of petrol filled at the kerbside is genuinely risky.
How it happens: petrol in a diesel
It is rarely carelessness, and nobody does it on purpose. The petrol nozzle is the slimmer of the two and slides into a diesel filler with almost no resistance; a diesel nozzle generally won't go into a petrol car at all. The forecourt makes it simple, and the error runs one way.
When habit and the vehicle stop matching, it happens. Hire cars, courtesy cars, and vehicles that are new to you. A household with one petrol and one diesel on the drive. A forecourt you know, only with its pumps arranged differently. A rushed fill on the way to Brighouse with a train to catch. Years of petrol vehicles behind you, a diesel Peugeot 308 in front of you on the forecourt for its first tank — that's when. Throw in rain, a phone call or a back seat full of children, and the hand repeats what it has always done.
Next time you fill up in The Crescent: preventing petrol in a diesel
- Green for unleaded and black for diesel is usual in the UK — yet not on each forecourt. Trust the label on the pump, not the colour.
- The first fill in a strange car is the time to check the filler flap — inside it, or on the cap, plenty of vehicles state the fuel they take.
- Label your key. In a household with one of each, a coloured fob or a sticker on the diesel's key does more than any amount of meaning to remember.
- Say it before you lift it. On your first fill in a new or hired car, say "diesel" out loud before you lift the nozzle off the petrol pump. It sounds daft and it does the trick.
- Put the phone away. This is an easy mistake to make whilst you're thinking about something else.
- Up to a point, a misfuel inhibitor helps: some diesels come with a filler designed to refuse a petrol nozzle, and add-on devices exist for the rest. Count it as a backstop, then keep checking the pump.
- As soon as you realise, stop: less petrol inside the tank makes a weaker blend. What to do next does not change, though — still do not crank it.
Petrol already in a diesel around The Crescent? Begin here
Then the order of things is short. Don't switch your ignition on, and do not fire it up. Still at the forecourt, at Tesco or anywhere else? Ask the attendants to help you push it away from the petrol pump. Then ring 0333 366 0103 and tell us what was put in, about how much, and if it's run.
Say so if it was AdBlue instead of petrol: it is a different issue, with its own page for The Crescent, because AdBlue brings corrosion and deposits rather than lost lubrication.
Why one petrol in a diesel job in The Crescent costs more than another
The four situations above are four separate jobs, so no single price for this would be honest. Which of them you're in is mostly what moves the cost. After that it's the proportion — how much petrol got in against how much that tank takes — and then where the car is and whether our van can get to it safely.
Three queries come first, before quoting, instead of after — what was put in, how much, has it run — and this is the reason. Those answers change a range into a straight figure.
About The Crescent itself
The Crescent is a locality situated on the riverside in West Yorkshire, with an elevation of 69 metres and a mix of terraced housing. The Crescent lies near several nearby places, including Brighouse, Slead Syke, and Thornhills, and is approximately 6 miles from the city of Bradford. The Crescent is part of the larger urban area surrounding Bradford, with the city's amenities and services within easy reach. The Crescent has a population of around 3897 people, according to recent estimates.
The Crescent and West Yorkshire: where our fuel drain cover reaches
Petrol in diesel call-outs in The Crescent — part of the HD postcode area — go to vans that also cover the spots about it, Brighouse, Slead Syke and Thornhills included. Our engineers drain where the vehicle is — your own driveway, a lay-by, a supermarket car park, a forecourt — so it does not have to come to us.
At the petrol pump around The Crescent, right now?
Then you're in the best position there is. Keep it off. Call.