Mersham: Petrol in a Diesel Car? How Worried to Be
Far less than you probably are, provided it hasn't been started. Everyone around Mersham begins with "have I ruined it?", and the fair answer is usually no: petrol left inside your tank of a diesel stays harmless until priming, cranking or driving pulls it into your fuel system. Leave the engine off and phone Petrol in Diesel — that keeps it like that. Further down, you will find what petrol really does inside a diesel, how far it may have gone, and how to stop it happening to you a second time.
The engine and petrol in a diesel: what happens
On its way through a motor, diesel does two tasks. It ignites, and before it ignites it protects. The high-pressure fuel pump and your injectors are made to very fine clearances, and your diesel passing through them is what stops those surfaces from wearing down against each other.
Of these two tasks, petrol manages the first poorly and the second never. A pump running on a petrol mixture is wearing itself out, since petrol is thinner than diesel and strips out the lubrication the fuel system depends on. Petrol is also made to resist igniting under compression — the reverse of what a diesel needs from its fuel — and that's where any clattering starts.
Together, those leave the shape of the trouble plain. The damage is done by movement, not by contact. Where that petrol is only inside that tank, it's a fault of fuel, nothing more. Whatever a worn pump sheds goes on, borne by your fuel, into the injectors further along, which is why a pump that has been working on that petrol is where a mechanical issue starts.
Four scenarios we see around Mersham: how bad is petrol in a diesel?
Fuelled but not once started — as good as it gets. Being at a forecourt is what makes this possible: elsewhere, the vehicle has been driven there to begin with. With the petrol kept in that tank alone, it's drained and cleaned right where it stands, and nothing more is needed.
Ignition on, or started for a moment. Once primed, your system has pulled petrol out of the tank up to the fuel filter and the fuel lines. That is generally still a straightforward task — a drain, a flush, and the fuel filter seen to.
Some miles driven, and your pump has spent each of them labouring on diluted fuel. The work is the tank, the fuel lines, your filter and clean fuel through the whole system, and how hard your car was driven counts as much as how far. On the school run to Mersham Primary School, the mileage is short. Any distance on the M20, under a mile from Mersham, means the engine has worked hard throughout, and a run to Canterbury, under 15 miles away, is a very different task too.
Driven on until it complained — knocking, smoke, a ragged idle, a soft throttle. That's your motor telling you its fuel has stopped behaving like diesel. Whether it is the verge on Oaklands, a lay-by or a side street, stop where you are and leave it. Lasting damage is very rare when a vehicle is stopped quickly, and the drain and flush that still go first sort it out.
Mersham people and the petrol in a diesel myths they hear
Myth: topping up to full with diesel makes it fine. It doesn't. Topping up removes nothing; it gives you a bigger tank of the same mix. That guidance supposes a diesel fuel system tolerates petrol by percentage. It doesn't.
"Newer diesels can handle a little petrol" — a myth, and nearer the opposite. At higher pressure, through more precise parts: that's how a current diesel moves its fuel, so the lubrication matters for more, not less.
One myth that catches people out: if it starts and drives, it must be unharmed. Diesel in a petrol motor usually leaves a motor that won't run: the motorist stops, and so does the damage. A diesel fed petrol usually starts, idles and drives away as if nothing has happened, while the pump wears. Running isn't the same as fine.
Not so: a two-stroke additive lets you to drive home. It is an old workaround, meant for another issue. What petrol has weakened stays diluted, and the petrol remains inside your tank anyway.
If your engine has been run, part of the petrol sits in the filter and the lines, not that tank — and the next start pulls it right back through the pump. So the myth "drain that tank yourself and you are sorted" does not hold. It is also truly dangerous to drain petrol into a can by the kerbside.
Petrol in a diesel: how does it take place?
On purpose? Never. Through carelessness? Rarely, if ever. The petrol nozzle is the slimmer of the two and slips into a diesel filler with almost no resistance; a diesel nozzle generally will not go into a petrol car at all. The forecourt makes it simple, and the error runs one way.
When routine and the vehicle stop matching, it takes place. Hire cars, courtesy cars, and motors that are new to you. A household with one petrol and one diesel on the drive. A familiar forecourt with the pumps in a different order. A rushed fill en route to Ashford International with a train to catch. Years of petrol cars behind you, a diesel Volkswagen Passat 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 does what it has always done.
Next time you fill up around Mersham: preventing petrol in a diesel
- Green for unleaded and black for diesel is normal in the UK — but not on each forecourt. Go by the label on the petrol pump, not the colour.
- In a car you do not know, look inside the flap over the filler or at the cap before the first fill: many cars state the fuel there.
- Good intentions do less than a sticker or a fob in a bright colour on the diesel's key if a house has one of each. So mark it.
- It sounds silly and it does the trick: on the first fill in a new or hired car, say "diesel" aloud before you take the nozzle off the pump.
- Thinking about something else is when this becomes an easy mistake to make, so put your phone away and keep your mind on the pump.
- A misfuel inhibitor helps, up to a point. Some diesels have a filler designed to refuse a petrol nozzle, and add-on devices exist for motors without one. They are a backstop, not a reason to stop checking the pump.
- Stop the moment you realise. Less petrol inside that tank makes a thinner mixture. It does not change what to do next, which is still not to start it.
Put petrol in a diesel around Mersham already?
Then the order of things is brief. Don't turn your ignition on, and do not start it. Ask the staff to help you push it away from the pump if you are still on the forecourt, whether that's Tesco or somewhere else. Next, 0333 366 0103. We'll ask what was put in, roughly how much, and if it has been run.
Corrosion and deposits form the issue with AdBlue, whereas petrol means lost protection. So if it was AdBlue, say so — and read its own Mersham page.
Why one petrol in a diesel job around Mersham costs more than another
The four situations above are four different jobs, so no single price for this would be honest. What moves your cost is mostly which of them you are in. The share matters next, meaning how much of that tank is petrol, and then the position of the car and whether reaching it is safe for a technician.
Ahead of any quote, not after, come three queries: your fuel that got in, its amount, and whether it's run. That is why. Given those answers, there is a straight figure rather than a range.
About Mersham, for a moment
Mersham is a small village in Kent, situated inland at an elevation of around 70 metres, and is located approximately 53 miles from London. Mersham has a population of around 770 people and is characterised by predominantly detached housing. Mersham is close to the nearby places of The Forstal, Sevington, and Ridgeway, and is about 12.7 miles from the city of Canterbury.
Fuel drain cover around Mersham and across Kent
The vans answering petrol in diesel calls in Mersham, in the TN postcode area, also work the locations around it, The Forstal, Sevington and Ridgeway among them. The vehicle doesn't need to come to us: our engineers drain at a forecourt, in a supermarket car park, in a lay-by or on your own drive.
Mersham: still at the petrol pump?
The best place there is, then — that's where you are. Keep it off. Call.