How Worried Should You Be? Petrol in a Diesel Car in Lower Wyche
If it hasn't been started, you can worry less than you likely are. Until the ignition primes the pump, your starter cranks, or the vehicle is driven, petrol in a diesel tank just rests there and does nothing. Which means the honest reply to the first Lower Wyche query — "have I ruined it?" — usually no. Petrol in Diesel is who to phone, with the motor left off, and so it stays that way. The remainder of this page sets out what petrol really does to a diesel, how to tell how far it has got, and how to make sure it doesn't happen to you again.
The motor and petrol in a diesel: what happens
On its way through a motor, diesel does two jobs. Lubricating comes before burning; it does both. What keeps the surfaces inside the high-pressure fuel pump and the injectors from grinding against each other is the diesel passing through them — they are made to very fine clearances.
The second job petrol doesn't do at all, and the first it does badly. It is runnier than diesel and takes away the protection your fuel system hinges on, and so a pump running on a petrol blend is a pump wearing itself. And petrol is designed to resist igniting under compression, which is the opposite of what a diesel needs from its fuel. That is where the knocking comes from.
Put these together and the shape of the issue is clear. Not contact but movement is what does the damage. Where the petrol is only inside that tank, it is a fault of fuel, nothing more. A pump that has been labouring on that petrol is the beginning of a mechanical one, and whatever a worn pump sheds moves on with your fuel to your injectors downstream.
Four scenarios our engineers see around Lower Wyche: how bad is petrol in a diesel?
Filled up, never started. The best case there can be. At a forecourt, and genuinely only there, the petrol is still limited to that tank — since anywhere else the car was driven to reach it. The task is emptying and rinsing on the spot.
Your ignition turned on, or a short start. The system has been bled, so petrol has left your tank and reached the filter and your lines. Normally little more than clearing, purging and sorting the fuel filter, so still easy.
A couple of miles driven, and the pump has spent each of them labouring on weakened fuel. Tank, lines, filter, then clean fuel run through the entire circuit: that's this work, and the way the car was driven counts as much as the miles. The school run to Malvern Wyche CofE Primary School is one matter. Any distance on the M5, under 10 miles from Lower Wyche, means the engine has worked hard throughout, and a run to Worcester, under 10 miles away, makes a very different task as well.
Driven on until it protested — clattering, smoke, a ragged idle, a dead throttle. The engine is telling you the fuel is no longer behaving like diesel. Whether it is the verge on Wyche Road, a lay-by or a side street, stop there and leave it. A vehicle pulled over quickly very seldom has long-term damage, as the fuel drain and the flush-through, which still go first, take care of it.
Stories Lower Wyche motorists hear about petrol in a diesel
"Top it up the rest of the way with diesel and it will be fine" — a myth. It will not. Nothing is removed by topping up — you're left with a bigger tank, still the same mixture. A diesel fuel system doesn't tolerate petrol by percentage in the way that guidance assumes.
"Current diesels can handle a little petrol" — a myth, and nearer the reverse. At higher pressure, through smaller parts: that's how a modern diesel handles its fuel, so the protection counts more, not less.
One myth that catches people out: if it starts and drives, it must be unharmed. Feed diesel to a petrol engine and it generally won't run, so the driver stops — and the harm stops with them. Feed petrol to a diesel and it normally starts, ticks over and drives away like nothing happened — all while its pump is wearing. Fine and running are not the same thing.
"A drop of two-stroke oil and drive it home" — a myth, borrowed from a fix from years ago, for a separate issue. The petrol is still in the tank afterwards, and whatever it has thinned isn't put back.
Myth: "Drain the tank yourself and you are sorted." After your engine has run, some of that petrol is no longer in your tank: it is in your filter and the lines, and it goes right back through your pump on the next start. Besides, petrol cleared into a can by the road is truly risky.
Why petrol in a diesel happens at all
A careless moment is rarely the cause, and no one means to do it. One way only, because of the nozzles: the smaller petrol one slips inside a diesel filler with almost no resistance, whereas the diesel one generally will not fit a petrol motor. That's how the forecourt makes it easy.
Routine and the car getting out of step is how it occurs. Courtesy car, hire car, or a vehicle that's new. One petrol and one diesel on the drive of the same household. Your normal forecourt, its pumps now in a different order. Racing for a train outside Great Malvern and filling up en route. A new-to-you diesel Renault Megane, its first fuelling, and a driver used to petrol: exactly when it takes place. The hand does what it has always done once you add rain, a phone call or a back seat full of children.
Preventing petrol in a diesel next time you fill up around Lower Wyche
- Read the petrol pump, not the colour. In the UK unleaded handles are usually green and diesel black, but not on each forecourt. The label is what matters.
- Check the filler flap. Plenty of cars state the fuel inside the flap or on the cap. Look at it on the first fill in any car you do not know.
- One of each in the household? Mark your key to your diesel — a bright fob, a sticker — since meaning to remember isn't enough.
- Before the nozzle leaves the pump the first time you fuel a hired or new car, say "diesel" aloud. Silly, perhaps, but it does the trick.
- While you're thinking about something else, this is an easy mistake to make — so tuck the phone away.
- Some diesels come with a filler designed to block a petrol nozzle, and devices you can add exist for vehicles without one. Such an inhibitor helps up to a point — as a safety net, not a reason to stop checking the pump.
- As soon as you notice, stop: less petrol in your tank makes a weaker mix. What to do next doesn't change, though — still don't fire it up.
Petrol already in a diesel in Lower Wyche? Start here
Short and simple, then, is the order of things. Don't crank it, and don't switch the ignition on. Still at the forecourt, at Texaco or anywhere else? Ask the staff to help you push the vehicle away from the pump. Ring 0333 366 0103 next, with three facts — the fuel, the rough quantity, and if it's run.
Corrosion and deposits form the issue with AdBlue, whereas petrol brings lost lubrication. So if it was AdBlue, say so — and see its own Lower Wyche page.
One petrol in a diesel job in Lower Wyche costs more than another. Why?
There's no fair single price for this, since the four situations above are four different jobs. The situation itself does most of the work of moving the cost. The share counts next, meaning how much of the tank is petrol, and then the position of your car and whether getting to it is safe for a technician.
Three queries come first, before any quote, instead of after — what got in, how much, has it run — and this is the reason. With the answers, there is a straight figure instead of a range.
About Lower Wyche itself
Lower Wyche is a suburban area situated in the Malvern Hills, approximately 8 miles southwest of Worcester, with an elevation of 221 metres. Lower Wyche is characterised by its predominantly detached housing stock, reflecting its development as a residential area. Lower Wyche sits near several nearby places, including Upper Wyche, Malvern Common, and Upper Colwall, and is around 103 miles west of London.
Fuel drain cover around Lower Wyche and across Worcestershire
Lower Wyche rests in the WR postcode area, and the vans that answer petrol in diesel jobs there work the spots around it as well — Upper Wyche, Malvern Common and Upper Colwall among them. A forecourt, a supermarket car park, a lay-by or your own drive are all spots our technicians work, and the vehicle doesn't need to come to us.
In Lower Wyche and still at the pump?
Then you're in the best position there is. Leave the car turned off, then ring.