How Worried Should You Be? Petrol in a Diesel Car in Tilehurst
Far less than you probably are, if it hasn't been started. Petrol resting in a diesel tank does nothing to the engine till something draws it through the system — the ignition priming your pump, your starter, or driving on its own. So the fair answer to the first question everyone in Tilehurst asks, "have I ruined it?", is usually no. To leave the car that way, call Petrol in Diesel and leave your engine switched off. The remainder of this page covers what petrol actually does to a diesel, how to judge how far it has got, and how to make sure it doesn't happen to you again.
Your engine and petrol in a diesel: what happens
Two jobs fall to diesel on its journey through a motor. Oiling comes before burning; it does both. The high-pressure fuel pump and the injectors are made to very fine tolerances, and the diesel passing through them is what keeps those surfaces from grinding against one another.
Petrol does the first job badly and the second not at all. Being less viscous than diesel, petrol strips away the lubrication a fuel system needs, so a pump running on the blend to wear itself. It is also made to resist igniting under compression — the reverse of what a diesel needs — which is where you get the rattling.
Taken together, they make clear what shape the trouble has. It's movement that does the harm, not contact. All a tank with petrol in it amounts to is a fuel problem. 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 your fuel to the injectors further on.
Tilehurst, petrol in a diesel: four cases, from mild to serious
Filled up, not once started. The best case there can be. Being on a forecourt is what makes this possible: elsewhere, the vehicle has been driven there to begin with. With that petrol held in your tank alone, it's cleared and flushed right where it stands, and nothing more is needed.
Ignition on, or started for a second. Petrol has left the tank and got to the filter and your lines, because the fuel system has been primed. Normally little more than clearing, flushing and sorting the filter, and so still easy.
Your pump now worked a couple of miles on thinned fuel — that is what driving the vehicle does. The work is that tank, the lines, the fuel filter and fresh fuel through the entire system, and how hard your car was driven matters as much as how far. Driving the children to Park Lane Primary School is one sort of trip. Very different a second time: a run to Oxford, under 25 miles away, or some miles on the M4, under 3 miles from Tilehurst, where your engine kept labouring hard.
Driven on till it complained — rattling, smoke, an uneven idle, a soft throttle. The fuel is not acting like diesel any more, and the engine is telling you. Leave it where it has stopped: a lay-by, a side street, the verge on Dunstall Close. A car pulled over early very seldom has lasting damage, because the fuel drain and the flush, which still come first, sort it out.
What Tilehurst motorists get told about petrol in a diesel — and the stories in it
"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. That guidance assumes a diesel fuel system handles petrol by percentage. It does not.
Myth: a modern diesel copes with a bit of petrol. If anything, the reverse. Finer parts and higher pressure are the way a modern diesel runs its fuel, and that makes the protection matter more, not less.
The myth that catches people off guard: if it starts and drives, it must be unharmed. Any petrol engine fed diesel usually won't run, so the motorist stops and the harm stops with them. A diesel fed petrol normally starts, idles and drives away as though nothing has happened, whilst your pump wears. A running engine doesn't mean fine.
"A drop of two-stroke oil and drive it home" — a myth, taken from a fix from years ago, for a separate fault. None of what petrol diluted is put back by it — and later, your tank still contains that petrol.
Myth: "Drain your tank yourself and you are sorted." After the motor has run, some of the petrol is no longer inside that tank: it's in the filter and the lines, and it goes right back through your pump at your next start. Also, a can of petrol drained by the kerbside is truly hazardous.
How does petrol in a diesel take place?
Nobody does it on purpose, and it's seldom carelessness. A diesel nozzle mostly won't go into a petrol motor, but the slimmer petrol nozzle goes into the filler of a diesel almost without resistance — so forecourts make this one error easy, and just in one direction.
It occurs when routine and your car stop matching. A new car, a hire car or a courtesy car. One petrol and one diesel on the drive of the same household. A forecourt you know, but with its pumps laid out differently. A train to catch, and a rushed fill en route to the nearest station. Precisely the moment it takes place: after years of driving petrol, a driver fills a diesel Renault Megane for the first time. The hand repeats what it has always done when you add rain, a phone call or a back seat full of children.
How to prevent petrol in a diesel at your next fill-up around Tilehurst
- Not every forecourt in the UK follows green for unleaded and black for diesel, though most generally do. Read the pump's label; the colour is just a hint.
- Plenty of motors state the fuel type inside the filler flap or on the cap, so check it on the first fill in any car you don't know.
- Label the key. In a household with one of each, a coloured fob or a sticker on your diesel's key does more than any amount of intending to remember.
- "Diesel", out loud, before you pick up the nozzle — every time a new or hired car gets its first tank. It seems silly. It does the trick.
- Thinking about something else is when this becomes an easy mistake to make, so put the phone away then keep your mind on the petrol pump.
- Add-on devices are available for motors without one, and some diesels are built with a filler that will not accept a petrol nozzle. Helpful — but a backstop at best, never a reason to stop checking the label.
- Stop as soon as you realise. Less petrol inside the tank makes a weaker mix. It does not change what to do next, which is still not to crank it.
Petrol already in a diesel in Tilehurst? Begin here
Then, there is just a short order of things. Starting it is out, and so is switching on the ignition. If you're still on the forecourt — Asda or anywhere else — ask the staff to help you roll it clear of the pump. What went in, about how much, and if it's run: tell us those when you phone 0333 366 0103.
Corrosion and deposits are the trouble with AdBlue, where petrol means lost lubrication. So if it was AdBlue, say so — and see its own Tilehurst page.
One petrol in a diesel job in Tilehurst costs more than another. Why?
The four situations above are four separate jobs, so no single price for this would be honest. The situation itself does most of the work of moving the cost. Two things come after that: the petrol that went in as a share of what the tank holds, then the place your car is in and whether a van can reach it safely.
Three queries come first, before quoting, rather than after — what got in, how much, has it run — and that is the reason. Those answers are what turn a range into one firm number.
About Tilehurst and where it is
Tilehurst is a suburban area in Berkshire, situated approximately 39 miles west of London and 22 miles south of Oxford. Tilehurst sits at an elevation of around 95 metres, near the neighbouring areas of Little Heath, Churchend, and Calcot Row. Tilehurst has a population of around 7893 people, predominantly living in semi-detached housing. Tilehurst is characterized by its inland setting, with a mix of residential and community facilities.
Tilehurst and Berkshire: where our fuel drain cover runs
Petrol in diesel call-outs around Tilehurst — part of the RG postcode area — go to vans that likewise cover the spots about it, Little Heath, Churchend and Calcot Row included. Our technicians drain where the vehicle is — your own drive, a lay-by, a supermarket car park, a forecourt — so it never needs to come to us.
At the pump in Tilehurst, still?
In that case, you couldn't be in a better place. Call, and leave it turned off.