Douglas: Petrol in a Diesel Car? How Worried to Be
Far less than you probably are, provided it hasn't been started. Everyone around Douglas starts with "have I ruined it?", and the honest answer is generally no: petrol resting inside that tank of a diesel stays harmless until priming, cranking or driving pulls it into your fuel system. Keep it like that: leave the engine off and phone Petrol in Diesel. The rest of this page covers what petrol actually does to a diesel, how to tell how far it has got, and how to make sure it doesn't happen to you again.
Inside your engine: what petrol in a diesel does
On its way through an engine, diesel has two jobs. Before it burns, it lubricates — and then it combusts. Designed to extremely fine tolerances, the injectors and the pump rely on the diesel moving through them to stop their surfaces wearing against one another.
Badly at the first, not at all at the second: that's petrol. A pump working on a petrol blend is wearing itself out, since petrol is thinner than diesel and takes away the lubrication the fuel system relies on. Petrol is also made to resist igniting under compression — the opposite of what a diesel needs from its fuel — and that's where any rattling comes.
Together, those make the shape of the issue clear. It's movement that does the damage, not contact. A tank with petrol in it is a fuel issue. Once your pump has been running on that petrol, a mechanical issue has begun: whatever is shed by a pump that's grinding travels downstream to the fuel injectors with your fuel.
Four scenarios our engineers see around Douglas: how bad is petrol in a diesel?
Fuelled up, not once started. The best case there is. At a forecourt, and genuinely only there, that petrol is still limited to the tank — since everywhere else the car was driven to get to it. The task is emptying and cleaning on the spot.
Ignition on, or started for a second. Petrol has come out of the tank and got to your filter and your lines, since the system has been bled. Usually nothing more than clearing, cleaning and seeing to the fuel filter, and so still simple.
The pump has spent a few miles on thinned fuel — that is what driving the car does. Tank, lines, filter, then clean fuel run through the whole circuit: that's this work, and the way the vehicle was driven counts as much as the miles. The school run to the local primary school is one thing. Driving as far as Glasgow, under 50 miles away, makes a very different task — as does any distance on the M74, under 3 miles from Douglas, with the engine running hard all the way.
Driven on till it protested — rattling, smoke, a ragged idle, a dead throttle. That is your engine telling you its fuel has stopped behaving like diesel. Leave it where it has stopped: a lay-by, a side street, the verge on Springhill Road. Lasting damage is very unusual when a car is pulled over early, and the drain and flush that still go first take care of it.
Douglas people and that petrol in a diesel stories they hear
False: topping up to full with diesel makes it fine. It does 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 advice supposes.
Myth: a current diesel copes with a bit of petrol. If anything, the reverse. At higher pressure, through finer components: that's how a modern diesel handles its fuel, and so the protection matters more, not less.
"It starts, it drives, and so there is no harm" — the myth that trips up more drivers than any other. Feed diesel to a petrol motor and it usually will not run, so the motorist stops — and the harm stops with them. Feed petrol to a diesel and it generally starts, idles and drives away like nothing has happened — all the while its pump wears. Being able to run is not the same as being fine.
"A drop of two-stroke oil and drive it home" — a myth, borrowed from a fix from years ago, for a distinct issue. None of what petrol diluted is put back by it — and later, that tank still holds that petrol.
"Drain it yourself and you are sorted" — a myth, because after it's been running some petrol lies in your filter and lines, ready to go straight back through your pump at the next start. And, a can of petrol filled at the kerbside is truly risky.
How petrol ends up: petrol in a diesel
A careless moment is rarely the cause, and nobody means to do it. A diesel nozzle mostly won't go into a petrol car, but the slimmer petrol nozzle goes into the filler of a diesel almost without resistance — so forecourts make this one mistake simple, and only in one direction.
It occurs when routine and the car stop matching. Courtesy car, hire car, or a motor that is new. Two motors on one driveway, one petrol, one diesel. Your usual forecourt, its pumps now in a different order. A train to catch, and a rushed fill en route to Lanark. Exactly the moment it takes place: after years of driving petrol, someone fills a diesel Volkswagen Golf for the first time. Add rain, a phone call or a back seat full of kids, and your hand repeats what it has always done.
How to avoid petrol in a diesel on your next fill-up in Douglas
- Not every forecourt in the UK keeps to green for unleaded and black for diesel, though most generally do. Read the petrol pump's label; the colour is only a hint.
- Plenty of cars state the fuel type inside the filler flap or on the cap, so check it on the first fill in any car you do not know.
- Good intentions do less than a sticker or a fob in a vivid colour on your diesel's key if a household has one of each. So mark it.
- It seems silly and it works: on your first fill in a new or hired car, say "diesel" aloud before you lift the nozzle off the petrol pump.
- While you are thinking about something else, this is an easy mistake to make — so tuck the phone away.
- Add-on devices exist for cars without one, and some diesels are built with a filler that won't accept a petrol nozzle. Helpful — but a backstop at best, never a reason to stop checking the label.
- Less petrol means a thinner blend, and so stop the moment you realise — though remembering that the next stage is unchanged. It is still not to fire it up.
Petrol already in a diesel in Douglas? Start here
Then, there's only a short order of things. Don't switch your ignition on, and do not crank it. Ask the attendants to help you push it away from the pump if you're still on the forecourt, whether that is Thames or anywhere else. Then ring 0333 366 0103 and tell us what got in, roughly how much, and whether it has run.
Say so if it was AdBlue rather than petrol: it's a different issue, with its own page for Douglas, since AdBlue brings corrosion and deposits rather than lost protection.
Douglas petrol in a diesel jobs: why one costs more than another
Four separate tasks lie behind the four situations above — which is why there is no fair single quote. Which of them you are in is chiefly what shifts the cost. Two things follow that: the petrol that went in as a proportion of what the tank takes, then the place the car is in and whether a technician can reach it safely.
Before any quote, not after, we ask three queries: your fuel that was put in, its amount, and whether it has run. That is why. Their replies are what change a range into one firm number.
About Douglas and its setting
Douglas is a village in South Lanarkshire, situated on the banks of a river at an elevation of 213 metres. Douglas sits in a rural area, approximately 26 miles from Glasgow and 318 miles from London. Douglas has a mix of housing types, but semi-detached homes are predominant in the village. Douglas is close to nearby settlements, including Douglas West, Uddington, and Glespin.
Douglas and South Lanarkshire: where our fuel drain cover runs
Douglas West, Uddington and Glespin are among the places around Douglas that the same vans work, answering petrol in diesel call-outs across Douglas's ML postcode area. No need to bring your vehicle to us. Forecourts, supermarket car parks, lay-bys and your own drive are all places where we work.
At the petrol pump in Douglas, still?
Then you are in the best spot there can be. Switched off it remains; then phone.