Upperthong: Petrol in a Diesel Car? How Worried to Be
Likely less than you are now — as long as no one has started the car. "Have I wrecked it?" is the first question everyone in Upperthong asks, and the honest answer is generally no, since petrol resting in a diesel tank hurts nothing till it is dragged through your fuel system — by ignition priming, by the starter, or by driving. Keep it that way: leave your motor off then ring Petrol in Diesel. Keep reading for three things: the effect petrol has inside a diesel engine, the signs of how far it has got, 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 route round a motor. It combusts, and before it combusts it lubricates. The high-pressure pump and your injectors are built to extremely fine gaps, and your diesel passing through them is what keeps those surfaces from grinding against one another.
Poorly at the first, not at all at the second: that's petrol. It is thinner than diesel and takes away the lubrication the fuel system depends on, so a pump running on a petrol mixture is a pump wearing itself. And petrol is made to resist igniting under compression, which is the reverse of what a diesel needs from its fuel. That's where the rattling comes from.
The shape of the issue is clear when you put those together. Contact does not do the harm — circulation does. All a tank with petrol in it amounts to is a fuel fault. Whatever a worn pump sheds travels on, borne by the fuel, into your injectors further along, which is why a pump that has worked on that petrol is where a mechanical issue starts.
Four scenarios our engineers see around Upperthong: how serious is petrol in a diesel?
Filled but not once started — the best it gets. At a forecourt, and really only there, the petrol is still limited to your tank — because everywhere else your car was driven to get to it. The task is emptying and rinsing on the spot.
A moment's running, or just your ignition on. Petrol has left your tank and reached the filter and the fuel lines, since the system has been primed. That's generally still a straightforward job — a drain, a flush, and the filter seen to.
Those few miles driven meant your pump working on fuel diluted by petrol the whole way. How hard your car was driven matters as much as how far, and this work takes in that tank, the lines, the filter and fresh fuel through the whole system. On the school run to Upperthong Junior and Infant School, the mileage is short. Driving as far as Wakefield, under 15 miles away, makes a very different task — as does any miles on the M62, under 10 miles from Upperthong, with the motor running hard all the way.
Knocking, a ragged idle, smoke, a throttle gone soft: driven till it complained. What you are hearing is the engine signalling fuel that no longer acts like diesel. Leave it wherever it has stopped: a lay-by, a quiet street, the verge on Netherhouses. What comes first is still the fuel drain and flush, and that deals with it, with permanent damage very unusual when a vehicle is stopped soon.
Petrol in a diesel stories Upperthong drivers hear
Myth: "Fill it the rest of the way with diesel and it'll be fine." It will not. A bigger tank of the same mix is all it gives, because topping up takes out nothing. The idea behind the advice — that diesel fuel systems tolerate petrol by percentage — is wrong.
"Newer diesels can handle a little petrol" — a myth, and closer to the opposite. Lubrication counts more on newer diesels, not less, because their fuel passes through more precise components at higher pressure.
Myth: "If it starts and drives, there is no harm done." This is the one that catches motorists. The driver of a petrol motor fed diesel usually stops, since it will not run, and the harm stops there. A diesel fed petrol generally starts, idles and drives away as though nothing has happened, whilst your pump grinds. A running engine doesn't mean fine.
"A drop of two-stroke oil and drive it home" — a myth, borrowed from a fix from years ago, for a separate fault. What petrol has thinned remains thinned, and that petrol stays in your tank regardless.
Once the engine has run, part of that petrol is in the filter and the fuel lines, not your tank — and your next start pulls it straight back through the pump. So the myth "drain the tank yourself and you are sorted" does not hold. And, a can of petrol filled by the roadside is genuinely dangerous.
Petrol in a diesel: how does it happen?
Carelessness is seldom the cause, and nobody means to do it. The petrol nozzle is the slimmer of the two and slides into a diesel filler with almost no resistance; a diesel nozzle generally will not go into a petrol vehicle at all. The forecourt makes it simple, and the error runs one way.
Routine and the vehicle falling out of step is when it happens. Any motor that is new to you — hired, on loan as a courtesy car, or brand new. Two vehicles on one drive, one petrol, one diesel. A forecourt you know, only with its pumps laid out differently. Filling up in a rush en route to Brockholes, with a train to catch. Precisely the moment it takes place: after years of driving petrol, someone fills a diesel Renault Megane for the first time. Throw in rain, a phone call or a back seat full of children, and your hand does what it has always done.
Next time you fill up in Upperthong: preventing petrol in a diesel
- Not every forecourt in the UK follows green for unleaded and black for diesel, even if most usually do. Check the pump's label; the colour is only a hint.
- The first fill in an unfamiliar vehicle is the time to check your filler flap — inside it, or on the cap, plenty of vehicles state the fuel they take.
- Mark your key. In a house with one of each, a coloured fob or a sticker on your diesel's key does more than any amount of meaning to remember.
- "Diesel", out loud, before you lift the nozzle — each time a new or hired car needs its first tank. It sounds silly. It works.
- Tuck your phone away. This is an easy mistake to make whilst you're thinking about something else.
- Some diesels come with a filler built to block a petrol nozzle, and devices you can add are available for motors without one. Such an inhibitor helps up to a point — as a backstop, not a reason to stop reading the pump.
- Less petrol means a weaker mixture, so stop as soon as you realise — while remembering that the next step is unchanged. It's still not to crank it.
Put petrol in a diesel around Upperthong already?
Then the order of things is short. Starting it is out, and so is switching on the ignition. The staff on the forecourt — whether at Murco itself or wherever you filled up — will normally help roll it away from the pump if you ask. Ring 0333 366 0103 next, with three facts — your fuel, the rough quantity, and whether it's run.
If it was AdBlue instead of petrol, say so. That is a separate issue — corrosion and deposits instead of lost protection — and it has its own page for Upperthong.
What makes one Upperthong petrol in a diesel task cost more than the next
There is no fair single quote for this, since the four scenarios above are four separate tasks. Which of them you are in is mostly what shifts the cost. The share counts next, meaning how much of that tank is petrol, and then the position of the car and whether reaching it is safe for a van.
Three queries come first, before quoting, instead of after — what went in, how much, has it run — and this is the reason. Those replies are what change a range into one firm number.
About Upperthong and its setting
Upperthong is a village in West Yorkshire, situated near the River Holme and characterised by its elevated position at around 249 metres. Upperthong has a mix of housing types, but detached homes are particularly prevalent in the area. Upperthong is located near several other small villages, including Liphill Bank and Burnlee, and is within commuting distance of Wakefield.
Upperthong and West Yorkshire: where our fuel drain cover runs
Petrol in diesel calls in Upperthong — part of the HD postcode area — go to teams that also cover the spots around it, Liphill Bank, Burnlee and Victoria included. A forecourt, a supermarket car park, a lay-by or your own drive are all spots our technicians work, and the car doesn't need to come to us.
Upperthong: still at the petrol pump?
The best spot there is, then — that's where you are. Call, and leave it switched off.