Croeserw: Petrol in a Diesel Car? How Worried to Be
Unstarted? Then less anxious than you likely feel. Till your ignition primes your pump, the starter turns, or the car is driven, petrol in a diesel tank just waits there and does no harm. Which makes the truthful reply to the first Croeserw query — "have I ruined it?" — normally no. To leave the car that way, ring Petrol in Diesel and leave your engine switched off. What petrol actually does to a diesel, how to judge how far it has travelled, and how to stop it from happening a second time: that is the remainder of this page.
Inside the engine: what petrol in a diesel really does
On its way through a motor, diesel does two tasks. It combusts, and before it burns it protects. What stops the surfaces inside your high-pressure pump and the fuel injectors from grinding against each other is the diesel passing through them — they're made to extremely fine gaps.
Petrol does the first task badly and the second not at all. 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's also made to resist igniting under compression — the opposite of what a diesel needs — which is why you get the clattering.
Combined, those leave the shape of the problem plain. It's movement that causes the damage, not contact. Petrol in a tank is a fuel fault. Whatever a worn pump sheds goes on, carried by the fuel, into the fuel injectors further along, which is why a pump that has worked on the petrol is where a mechanical problem starts.
How bad is petrol in a diesel? Four situations our technicians see around Croeserw
Filled up, not once started. The best case there can be. Only that tank has petrol in it, so the job is emptying your tank and rinsing the system where your car stands. This situation can only really take place at a forecourt: anywhere else, the car got there by being driven.
A brief spell of running, or merely the ignition on. Petrol has come out of your tank and got to the filter and the lines, since the system has been bled. Drain, flush, deal with the fuel filter: still usually straightforward.
Driven a few miles. Now the pump has spent these miles working on diluted fuel. Tank, lines, filter, then fresh fuel put through the entire system: that's this work, and the way your car was driven matters as much as the distance. Short trips, such as the school run to the local primary school, are one thing. A run as far as Swansea, under 15 miles away, is a very different task. So is any miles on the M4, under 10 miles from Croeserw, where the engine has been working hard throughout.
It protested, and only then stopped: smoke, clattering, a throttle gone soft, an idle gone lumpy. The motor is telling you the fuel is no longer acting like diesel. Leave it wherever it stops: a lay-by, a side street, the verge on South Avenue. The fuel drain and flush still go first, and they deal with it: when a car is pulled over quickly, lasting damage is very uncommon.
Petrol in a diesel myths Croeserw motorists hear
It will not be fine. The myth: "Fill it the rest of the way with diesel and it'll be." Nothing is removed when you top up — your tank simply holds more of the same blend. The assumption behind that advice — that diesel fuel systems tolerate petrol by percentage — is wrong.
"Modern diesels can handle a little petrol" — a myth, and closer to the opposite. Smaller components and higher pressure are the way a newer diesel runs its fuel, and that makes the protection matter more, not less.
"It starts, it drives, and so no harm done" — the myth that trips up more drivers than any other. The motorist of a petrol engine fed diesel usually stops, because it will not run, and the damage stops with them. A diesel fed petrol normally starts, ticks over and drives away as though nothing has happened, whilst the pump wears. Running isn't the same as fine.
Myth: a two-stroke additive makes it safe to drive home. It was an old workaround, meant for another issue. None of what petrol thinned gets put back by it — and later, that tank still contains the petrol.
The next start draws petrol back round the pump from the lines and your filter, where some of it sits after the engine has been run. That is why draining the tank yourself does not leave you sorted — a myth. And, a can of petrol filled by the kerbside is truly hazardous.
How does petrol in a diesel happen?
On purpose? Never. Through carelessness? Rarely, if ever. A diesel nozzle generally won't fit a petrol motor, yet the narrower petrol nozzle goes into the filler of a diesel nearly without resistance — so forecourts make this one mistake simple, and just in that direction.
It happens when routine and the vehicle stop matching. Courtesy car, hire car, or a car that's brand new. Two motors on one driveway, one petrol, one diesel. A forecourt you know, but with its pumps arranged differently. Racing for a train outside Maesteg and filling up en route. Precisely the moment it takes place: after years of driving petrol, someone fills a diesel Volkswagen Golf for the first time. Your hand does what it has always done when you add rain, a phone call or a back seat full of kids.
Croeserw drivers: how to prevent petrol in a diesel next time
- A green handle for unleaded and black for diesel is usual in the UK — yet not on each forecourt. Trust the label on the pump, not the colour.
- In a car you don't know, look inside the flap over your filler or at the cap before your first fill: plenty of vehicles print the fuel type there.
- 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 meaning to remember.
- "Diesel", aloud, before you pick up the nozzle — each time a new or hired car needs 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 come with a filler designed to reject a petrol nozzle, and devices you can add are available for vehicles without one. Such an inhibitor helps up to a point — as a safety net, not a reason to stop reading the petrol pump.
- Stop as soon as you notice. Less petrol in that tank means a thinner blend. It does not change what to do next, which is still not to fire it up.
Croeserw: already put petrol in a diesel?
Short and simple, then, is the order of things. Don't turn the ignition on, and don't fire it up. Ask the staff to help you push it clear of the petrol pump if you are still on the forecourt, whether that's Oils for Wales or somewhere else. What got in, about how much, and whether it has run: tell us those when you phone 0333 366 0103.
AdBlue, not petrol? Then say so. Corrosion and deposits, not lost lubrication, make it a separate issue — Croeserw has a page just for it.
Why one petrol in a diesel task around Croeserw costs more than another
There's no fair single price for this, since the four situations above are four different jobs. Mostly, your cost shifts with which one you are in. Next it is the proportion — how much petrol was put in against how much the tank holds — and then where the car is and whether a van can get to it safely.
What was put in, how much, and if it's run — three questions our technicians ask before pricing, not after, for exactly that reason. With the replies, there is a straight figure rather than a range.
About Croeserw, for a moment
Croeserw is a village in Neath Port Talbot, situated on the riverside at an elevation of 247 metres. Croeserw lies near the communities of Cymmer, Blaencaerau, and Brynheulog, and is approximately 13 miles from Swansea. Croeserw has a population of around 1455 people, predominantly living in semi-detached housing. Croeserw is located in a scenic area, with the village surrounded by Welsh countryside.
Fuel drain cover across Neath Port Talbot, Croeserw included
Cymmer, Blaencaerau and Brynheulog are among the spots near Croeserw that the same vans work, answering petrol in diesel call-outs across Croeserw's SA postcode area. The vehicle doesn't need to move to us: our engineers drain at a forecourt, in a supermarket car park, in a lay-by or on your own driveway.
Croeserw: still at the pump?
Then you're in the best position there can be. Turned off it remains; then call.