Sully: Petrol in a Diesel Car? How Worried to Be
Unstarted? Then less worried than you probably feel. "Have I wrecked it?" is the first thing everyone in Sully asks, and the honest answer is normally no, because petrol left in a diesel tank hurts nothing till it is dragged through the fuel system — by ignition priming, by your starter, or by driving. Leave the engine off then phone Petrol in Diesel — that is how you keep it that way. Read on for three things: the effect petrol has inside a diesel motor, the signs of how far it has spread, and ways to make sure you don't repeat it.
Your engine and petrol in a diesel: what happens
Two jobs fall to diesel on its journey through a motor. Before it ignites, it lubricates — and then it ignites. Built to extremely fine tolerances, the injectors and the pump depend on your diesel flowing through them to keep their surfaces from wearing against one another.
Badly at the first, not at all at the second: that is petrol. Being less viscous than diesel, petrol strips out the lubrication a fuel system needs, leaving a pump running 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 knocking.
Put these together and the shape of the trouble is plain. Not contact but movement is what does the harm. Petrol in a tank is a fuel fault. A pump that has been working on that petrol is the beginning of a mechanical one, and whatever a worn pump sheds moves on with the fuel to the fuel injectors downstream.
How serious is petrol in a diesel? Four scenarios we see in Sully
Filled up, and never started: nothing beats it. Only your tank has petrol in it, so the task is emptying that tank and rinsing the system where the car sits. This situation can only really take place at a forecourt: anywhere else, the vehicle got there by being driven.
Started for a moment, or just your ignition on. Once primed, the fuel system has pulled petrol out of your tank as far as your filter and the fuel lines. Still generally straightforward: drain, flush, and your filter dealt with.
The pump has spent a couple of miles on diluted fuel — that is what driving the vehicle meant. How hard your car was driven counts as much as how far, and this work takes in the tank, your lines, the fuel filter and clean fuel through the whole circuit. On the school run to the local primary school, the miles is small. Driving as far as Cardiff, under 10 miles away, makes a very different job — as does any mileage on the M4, under 10 miles from Sully, with your engine running hard the whole time.
It complained, and only then stopped: smoke, clattering, a throttle gone soft, an idle gone ragged. That is the motor telling you its fuel has stopped behaving like diesel. Whether it is the verge on Minehead Avenue, a lay-by or a side street, stop where you are and leave it. Long-term damage is very uncommon if a vehicle is pulled over early, and the fuel drain and flush that still go first sort it out.
Myths Sully motorists hear about petrol in a diesel
Myth: topping up to full with diesel makes it fine. It does not. A fuller tank of the same mixture is all it gives, since topping up removes nothing. A diesel fuel system doesn't tolerate petrol by percentage in the way that advice presumes.
Myth: a newer diesel copes with a bit of petrol. Rather, the opposite. A newer diesel sends its fuel through more precise parts at higher pressure, which makes the protection matter more, not less.
Myth: "If it starts and drives, there is no damage done." This is the one that fools drivers. Feed diesel to a petrol engine and it generally won't run, and so the motorist stops — and the damage stops with them. Whilst your pump wears, a diesel fed petrol normally starts, ticks over and drives away as if nothing has happened. Being able to run is not the same as being fine.
Myth: "Add some two-stroke oil and drive it home." It is an old workaround for a separate problem. What petrol has thinned remains thinned, and the petrol remains inside your tank anyway.
"Drain it yourself and you are sorted" — a myth, since after it's been running some petrol lies in your filter and lines, waiting to go right back through your pump at your next start. It is also genuinely dangerous to drain petrol into a can by the roadside.
How does petrol in a diesel occur?
It is seldom carelessness, and nobody does it on purpose. The forecourt makes it simple: the petrol nozzle is the slimmer of the two, and it slips into a diesel filler with almost no resistance, while a diesel nozzle generally won't go into a petrol vehicle at all. So the mistake runs one way.
Routine and the vehicle getting out of step is how it happens. Courtesy car, hire car, or a vehicle that is new. One petrol and one diesel on the driveway of the same household. Your normal forecourt, its pumps now in a different order. A hurried fill on the way to Cadoxton with a train to catch. The first fill-up in a diesel Volkswagen Tiguan after years of driving petrol is precisely the moment it happens. With rain, a call arriving, or a car full of children to deal with, your hand simply does what it always has.
Avoiding petrol in a diesel next time you fill up around Sully
- Check the petrol pump, not the colour. In the UK unleaded handles are normally green and diesel black, yet not on each forecourt. The label is what matters.
- Inspect your filler flap. Plenty of vehicles state the fuel type inside the flap or on the cap. Look at it on your first fill in any vehicle you don't know.
- Good intentions do less than a sticker or a fob in a vivid colour on the diesel's key if a home has one of each. So label it.
- It sounds silly and it works: on the first fill in a new or hired car, say "diesel" aloud before you lift the nozzle off the petrol pump.
- Put your phone away. This is an easy mistake to make while you are thinking about something else.
- A misfuel inhibitor helps, up to a point. Some diesels come with a filler built to reject a petrol nozzle, and add-on devices exist for motors without one. They are a backstop, not a reason to stop checking the pump.
- Less petrol makes a weaker blend, and so stop as soon as you realise — though remembering that the next stage is unchanged. It is still not to fire it up.
Already put petrol in a diesel in Sully?
Then the order of things is brief. Do not crank it, and do not switch the ignition on. The attendants at the forecourt — whether at Cardiff Gas - autogas itself or wherever you filled up — will usually help roll it clear of the pump if you ask. What went in, roughly how much, and whether it's run: tell us those when you ring 0333 366 0103.
If it was AdBlue instead of petrol, say so. That is a separate issue — corrosion and deposits rather than lost lubrication — and it has its own page for Sully.
Why one petrol in a diesel job in Sully costs more than another
Four different jobs sit behind the four situations above — which is why there is no honest single price. What shifts your cost is chiefly which of them you are in. The ratio matters next, meaning how much of the tank is petrol, and then the location of the car and whether getting to it is safe for our van.
Ahead of any quote, not after, come three questions: the fuel that went in, its quantity, and if it's run. That's why. Those answers are what turn a range into one firm number.
About Sully and its setting
Sully is a coastal suburban area in The Vale of Glamorgan, situated near the mouth of the Bristol Channel, with Swanbridge and Cog to the west. Sully sits at an elevation of around 23 metres, looking out over the sea towards the English coast. Sully has a mix of housing types, but detached homes are particularly prevalent in the area. Sully is located close to Cardiff, the capital city of Wales, which is about 5 miles to the northeast.
Fuel drain cover across The Vale of Glamorgan, Sully included
Swanbridge, Cog and Palmerstown are among the locations near Sully that the same teams work, answering petrol in diesel call-outs across Sully's CF postcode area. A forecourt, a supermarket car park, a lay-by or your own drive are all locations our engineers drain, and your car doesn't need to move to us.
Still at the pump in Sully?
Then, you could not be in a better position. Turned off it remains; then ring.