Should You Worry? Petrol in a Diesel Car in The Lakes
If it hasn't been started, worry far less than you probably are. Petrol sitting in a diesel tank does nothing to the engine until something draws it through the fuel system — the ignition priming your pump, your starter, or the drive itself. So the fair answer to the first question everyone around The Lakes asks, "have I wrecked it?", is generally no. To leave the car that way, call Petrol in Diesel then leave the engine alone. Keep reading for three things: the effect petrol has inside a diesel motor, the clues of how far it has got, and ways to make sure you never repeat it.
The motor and petrol in a diesel: what happens
Diesel has two tasks on its way through an engine. Before it combusts, it protects — then it burns. Your high-pressure pump and the fuel injectors are made to extremely fine tolerances, and the diesel passing through them is what stops those surfaces from wearing down against each other.
Badly at the first, not at all at the second: that's petrol. Being less viscous than diesel, petrol strips away the lubrication a fuel system needs, so a pump on the mixture to wear itself. It's also made to resist igniting under compression — the reverse of what a diesel needs — which is where you hear the rattling.
Together, those leave the shape of the issue clear. It is movement that does the damage, not contact. A tank with petrol in it is a fuel fault. Once the pump has been working on that petrol, a mechanical problem has begun: anything shed by a pump that is wearing down travels downstream to your injectors with the fuel.
How serious is petrol in a diesel? Four scenarios our technicians see in The Lakes
Filled but not once started — the best it gets. At a forecourt, and genuinely only there, that petrol is still limited to that tank — because everywhere else the car was driven to reach it. The job is draining and cleaning on the spot.
The ignition switched on, or a brief start. Petrol has come out of the tank and got to your filter and your lines, because your system has been bled. Drain, flush, deal with the fuel filter: still normally simple.
Driven a few miles. Now your pump has spent those miles working on thinned fuel. Mileage is only half of it; how hard it was driven matters equally. Either way this work includes your tank, your lines, the fuel filter and fresh fuel through the entire circuit. A school run to St Anne's CofE VC Primary School is one matter. Very different once more: a run to Worcester, under 15 miles away, or some miles on the M5, under 15 miles from The Lakes, where the motor never stopped running hard.
It protested, and only then stopped: smoke, knocking, a throttle gone soft, an idle gone uneven. The engine is telling you the fuel is no longer acting like diesel. Whether it is the verge on Yew Tree Lane, a lay-by or a side street, stop where you are and leave it. A vehicle pulled over quickly very seldom has long-term damage, because the drain and the flush-through, which still go first, sort it out.
What The Lakes drivers get told about petrol in a diesel — and the stories in it
False: topping up to full with diesel makes it fine. It doesn't. Topping up takes out nothing; it gives you a fuller tank of the same mix. Percentage isn't how a diesel fuel system tolerates petrol, whatever that guidance supposes.
Myth: "A modern diesel can cope with a bit of petrol." If anything, the reverse. Smaller parts and higher pressure are the way a newer diesel runs its fuel, and that makes the lubrication count more, not less.
The myth that catches drivers 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 motorist stops — and the harm stops with them. Nothing seems to have happened when a diesel fed petrol fires up, ticks over and drives away, which it usually does; meanwhile your pump wears. Being able to run isn't the same as being fine.
Myth: "Add some two-stroke oil and drive the car home." It is an outdated fix for a separate issue. None of what petrol diluted gets put back by it — and later, that tank still holds the petrol.
Once the engine has run, part of the petrol sits in the filter and the fuel lines, not your tank — and the next start sends it straight back through your pump. So the myth "drain your tank yourself and you're sorted" doesn't hold. On top of that, petrol drained into a can by the road is genuinely dangerous.
Why petrol in a diesel takes place so easily
No one does it on purpose, and it's rarely carelessness. The forecourt makes it easy: the petrol nozzle is the narrower of the two, and it slips into a diesel filler with almost no resistance, whilst a diesel nozzle generally will not go into a petrol motor at all. So the mistake runs one way.
Habit and the vehicle getting out of step is how it takes place. A vehicle that's new to you — hired, on loan as a courtesy car, or brand new. Two motors on one driveway, one petrol, one diesel. A forecourt you know, but with its pumps arranged differently. Rushing for a train outside Kidderminster and fuelling up en route. A new-to-you diesel Volkswagen Golf, its first fuelling, and a driver used to petrol: precisely when it happens. Throw in a back seat full of children, a phone call or rain, and the hand takes over.
How to avoid petrol in a diesel at your next fill-up in The Lakes
- The label is what counts, so check the petrol pump rather than the colour: in the UK unleaded handles are normally green and diesel black, but not on each forecourt.
- Many motors state the fuel type inside the filler flap or on the cap, so check there on your first fill in any vehicle you do not know.
- A coloured fob or a sticker on the diesel's key does more than any amount of meaning to remember, for a house with one of each.
- It sounds silly and it does the trick: on your first fill in a new or hired car, say "diesel" out loud before you lift the nozzle off the petrol pump.
- Put your phone away. This is an easy mistake to make whilst you're thinking about something else.
- Add-on devices are available for cars without one, and some diesels come with a filler that won't accept a petrol nozzle. Helpful — but a safety net only, never a reason to stop checking the label.
- Less petrol makes a weaker mix, so stop the moment you realise — though remembering that the next stage is unchanged. It is still not to start it.
Already put petrol in a diesel in The Lakes?
The order of things is short, then. Starting it is out, and so is switching on the ignition. Still on the forecourt, at Texaco or anywhere else? Ask the staff to help you roll the vehicle away from the petrol pump. Next, 0333 366 0103. We'll ask what got in, roughly how much, and if it has been run.
AdBlue, not petrol? Then tell us. Corrosion and deposits, not lost lubrication, make it a different issue — The Lakes has a page just for it.
Why one petrol in a diesel task around The Lakes costs more than another
There's no honest single quote for this, because the four situations above are four different tasks. Mostly, the cost shifts with which one you are in. The ratio matters next, meaning how much of your tank is petrol, and then the location of the vehicle and whether reaching it is safe for a van.
Three queries come first, before quoting, instead of after — what got in, how much, has it run — and this is the reason. A range turns into a straight figure once the answers are in.
About The Lakes
The Lakes is a suburban area in Worcestershire, situated inland at an elevation of 81 metres, approximately 13.5 miles from Worcester. The Lakes is characterised by its predominantly detached housing stock, with nearby places including Bark Hill, Hales Park, and Hawthorn Bush. The Lakes is home to a population of around 4039 residents, and is located 111.3 miles from London.
Across Worcestershire and in The Lakes: fuel drain cover
Bark Hill, Hales Park and Hawthorn Bush are among the locations around The Lakes that the same teams work, answering petrol in diesel call-outs across The Lakes's DY postcode area. The car doesn't need to move to us: our technicians drain at a forecourt, in a supermarket car park, in a lay-by or on your own drive.
The Lakes: still at the pump?
The best position there is, then — that is where you are. Turned off it remains; then phone.