Selhurst: Petrol in a Diesel Car? How Worried to Be
Not started? Then less anxious than you likely are. Until your ignition primes your pump, the starter cranks, or the car is driven, petrol in a diesel tank simply waits there and does nothing. Which makes the truthful reply to that first Selhurst question — "have I ruined it?" — normally no. Petrol in Diesel is who to phone, with the motor kept off, and so it stays that way. The rest of this page sets out what petrol really does to a diesel, how to judge how far it has got, and how to make sure it doesn't happen to you a second time.
Your engine and petrol in a diesel: what happens
Diesel does two tasks on its way through an engine. It lubricates to begin with, and only then does it burn. What keeps the surfaces inside the high-pressure pump and the fuel injectors from wearing down against one another is your diesel flowing through them — they are designed to extremely fine clearances.
Badly at the first, not at all at the second: that's petrol. Being less viscous than diesel, petrol strips out the lubrication a fuel system needs, so a pump running on the mixture to wear itself. It is equally made to resist igniting under compression — the reverse of what a diesel needs — which is why you get the clattering.
Combined, those leave the shape of the issue plain. Not contact but circulation is what causes the harm. All a tank with petrol in it amounts to is a fuel fault. After the pump has been working on that petrol, a mechanical problem has begun: whatever is shed by a pump that is grinding is carried onward to the injectors with the fuel.
Selhurst, petrol in a diesel: four situations, from mild to serious
The best case there can be: filled up, not once started. At a forecourt, and really only there, the petrol is still confined to the tank — since anywhere else the car was driven to get to it. The task is draining and rinsing on the spot.
Ignition on, or started for a moment. With the system primed, the lines and filter already contain petrol that has come from the tank. Still normally easy: drain, flush, and the fuel filter sorted.
The pump now spent a couple of miles on thinned fuel — that is what driving it does. Miles is only half of that; how hard it was driven counts just as much. Either way this work runs to the tank, the fuel lines, the filter and fresh fuel through the entire system. On the school run to Broadmead Primary School, the mileage is small. Any miles on the M23, under 10 miles from Selhurst, means your engine working hard throughout, and a run to Westminster, under 10 miles away, makes a very different job too.
Rattling, a ragged idle, smoke, a throttle gone soft: driven till it complained. The engine is telling you your fuel is no longer acting like diesel. Stop wherever you are — the verge on Owen Close, a lay-by, a side street — then leave it there. What comes first is still the drain and flush-through, and that deals with it, with permanent damage very rare when a vehicle is stopped early.
Petrol in a diesel stories Selhurst people hear
It will not be fine. The myth: "Fill it the rest of the way with diesel and it will be." Nothing is removed by topping up — you're left with a bigger tank, still the same mixture. The idea behind that advice — that diesel fuel systems accept petrol by percentage — is wrong.
"Modern diesels can handle a little petrol" — a myth, and closer to the reverse. At higher pressure, through finer parts: that's how a newer diesel handles its fuel, and so the lubrication matters more, not less.
"It starts, it drives, so no harm done" — the myth that catches more drivers than any other. The driver of a petrol motor fed diesel usually stops, because it will not run, and the harm stops there. While your pump wears, a diesel fed petrol usually starts, ticks over and drives away as if nothing has happened. Running doesn't mean fine.
Myth: "Add some two-stroke oil and drive the vehicle home." It's an old workaround for a separate issue. None of what petrol thinned gets put back by it — and later, the tank still contains the petrol.
If your engine has run, part of the petrol sits in the fuel filter and your lines, not your tank — and your next start sends it straight back through the pump. So the myth "drain your tank yourself and you're sorted" doesn't stand up. Besides, petrol cleared into a can by the road is genuinely dangerous.
How petrol ends up: petrol in a diesel
It's seldom carelessness, and no one does it on purpose. The petrol nozzle is the narrower of the two and slips into a diesel filler with almost no resistance; a diesel nozzle mostly won't go into a petrol motor at all. The forecourt makes it simple, and the error runs one way.
When habit and the car stop matching, it takes place. A vehicle that's new to you — hired, on loan as a courtesy car, or just bought. One petrol and one diesel on the driveway of the same household. Your normal forecourt, its pumps suddenly in a different order. A rushed fill en route to the nearest station with a train to catch. The first fill-up in a diesel Volkswagen Golf after years of driving petrol is precisely the moment it occurs. Your hand does what it has always done when you add rain, a phone call or a back seat full of kids.
Selhurst drivers: how to prevent petrol in a diesel next time
- Not every forecourt in the UK keeps to green for unleaded and black for diesel, even if most generally do. Check the pump's label; the colour is just a hint.
- Inspect your filler flap. Plenty of motors state the fuel type inside the flap or on the cap. Look at it on the first fill in any motor you do not know.
- Label 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", aloud, before you pick up the nozzle — each time a new or hired car gets its first tank. It sounds silly. It works.
- Mistakes like this are simple to make while your mind is on something else, and so your phone goes away.
- Some diesels have a filler designed to reject a petrol nozzle, and devices you can add are available for cars without one. Such an inhibitor helps up to a point — as a safety net, not a reason to stop checking the pump.
- Stop the moment you realise. Less petrol in the tank means a thinner blend. It does not change what to do next, which is still not to start it.
Petrol already in a diesel around Selhurst? Begin here
Short and simple, then, is the order of things. Don't fire it up, and don't switch the ignition on. Yet on the forecourt, at Shell or anywhere else? Ask the attendants to help you push it clear of the pump. Next, 0333 366 0103. We will ask what was put in, about how much, and if it has been run.
AdBlue, not petrol? Then say so. Corrosion and deposits, not lost lubrication, make it a separate fault — Selhurst has a page all for it.
What makes one Selhurst petrol in a diesel job cost more than the next
There is no honest single price for this, since the four situations above are four separate jobs. The scenario itself does most of the work of moving the cost. The proportion counts next, meaning how much of the tank is petrol, followed by the position of your car and whether getting to it is safe for a van.
That's why our engineers ask three queries before quoting instead of after: what went in, how much, and whether it's run. Their replies are what change a range into one firm number.
About Selhurst
Selhurst is a suburban area in south London, situated near the River Effra and close to the neighbouring areas of Broad Green, Woodside, and South Norwood. Selhurst sits at an elevation of around 54 metres, approximately 8.4 miles from central London. Selhurst is characterized by its predominantly flat-type housing, which reflects the typical residential development of the area. Selhurst is home to around 11,970 residents, according to approximate population figures.
Fuel drain cover around Selhurst and across Greater London
Selhurst rests in the CR postcode area, and the vans that answer petrol in diesel jobs there work the locations near it as well — Broad Green, Woodside and South Norwood among them. The car doesn't need to move to us: we drain at a forecourt, in a supermarket car park, in a lay-by or on your own driveway.
Still at the petrol pump around Selhurst?
No position is better: that is where you now are. Keep it off. Call.