Brooklands: Petrol in a Diesel Car? How Worried to Be
Provided it hasn't been started, worry less than you probably are. Until the ignition primes the pump, the starter turns, or the vehicle is driven, petrol in a diesel tank just waits there and does no harm. Which makes the honest reply to that first Brooklands question — "have I ruined it?" — usually no. Leave your engine off then ring Petrol in Diesel — that is how you keep it that way. Further down, this page sets out what petrol actually does inside a diesel, how far it may have gone, and how to stop it happening to you a second time.
Inside your engine: what petrol in a diesel really does
On its way through an engine, diesel does two jobs. Oiling comes before burning; it does both. What keeps the surfaces inside the high-pressure fuel pump and the fuel injectors from wearing against one another is your diesel passing through them — they are built to extremely fine tolerances.
Petrol does the first task badly and the second not at all. It is thinner than diesel and takes away the protection the fuel system rests on, and so a pump running on a petrol mix 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's where the rattling comes from.
Combined, those leave the shape of the problem clear. Contact doesn't do the harm — circulation does. Where that petrol is only in the tank, it's a fault of fuel, nothing more. The beginning of a mechanical problem is a pump that has been labouring on that petrol — and whatever a worn pump sheds travels on with your fuel to your injectors beyond it.
Brooklands, petrol in a diesel: four situations, from mild to serious
Filled up, never started. The best case there is. At a forecourt, and genuinely only there, that petrol is still limited to the tank — since anywhere else the vehicle was driven to reach it. The task is emptying and flushing on the spot.
A moment's running, or just your ignition on. With the fuel system primed, the lines and filter now hold petrol that has come from the tank. Normally little more than clearing, purging and sorting the filter, so still simple.
The pump now worked a couple of miles on diluted fuel — that's what driving the car does. How hard the vehicle was driven matters as much as how far, and this work takes in that tank, your lines, the fuel filter and clean fuel through the entire system. On the school run to Brooklands Primary School, the miles is small. Driving as far as Salford, under 5 miles away, makes a very different task — as does any miles on the M60, under 3 miles from Brooklands, with the engine labouring hard all the way.
Driven on until it complained — knocking, smoke, an uneven idle, a dead throttle. The fuel isn't acting like diesel any more, and the engine is saying so. Pull up wherever you are — the verge on Brooklands Road, a lay-by, a side street — then leave the car where it is. A vehicle pulled over soon very seldom has permanent damage, as the drain and the flush-through, which still go first, take care of it.
Petrol in a diesel myths Brooklands 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 fuller tank, still the same mixture. The idea behind the guidance — that diesel fuel systems accept petrol by percentage — is wrong.
"Modern diesels can handle a little petrol" — a myth, and closer to the opposite. Finer components and higher pressure are the way a current diesel runs its fuel, and that makes the lubrication matter more, not less.
Myth: "If it starts and drives, there's no harm done." This is the one that catches motorists. A petrol motor fed diesel generally won't run, so the driver stops and the damage stops with them. Feed petrol to a diesel and it generally starts, idles and drives away like nothing has happened — all while its pump is wearing. Running isn't the same as fine.
An old fix for a different issue is behind this one. Myth: "Add some two-stroke oil and drive it home." What petrol has diluted remains thinned, and the petrol remains in the tank regardless.
The next start draws petrol back round the pump from the lines and the filter, where some of that ends up once the engine has been run. That is why a DIY tank drain does not sort it — a myth. On top of that, petrol drained into a can by the road is genuinely hazardous.
How does petrol in a diesel take place?
No one does it on purpose, and it's seldom carelessness. The forecourt makes it easy: the petrol nozzle is the narrower of the two, and it slips into a diesel filler with almost no resistance, while a diesel nozzle generally won't go into a petrol motor at all. So the mistake runs one way.
When routine and the vehicle stop matching, it happens. Courtesy car, hire car, or a motor that's brand new. A household with one petrol and one diesel on the driveway. A forecourt you know, but with its pumps laid out differently. A train to catch, and a rushed fill en route to Navigation Road. Years of petrol vehicles behind you, a diesel BMW 3 Series in front of you on the forecourt for its first tank — that's when. Throw in a back seat full of children, a phone call or rain, and the hand takes over.
Preventing petrol in a diesel next time you fill up around Brooklands
- Check the pump, not the colour. In the UK unleaded handles are normally green and diesel black, but not on every forecourt. The label is what matters.
- Check the filler flap. Plenty of vehicles state the fuel type inside the flap or on the cap. Look at it on your first fill in a car you do not know.
- Mark your key. In a home with one of each, a coloured fob or a sticker on the 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 needs its first tank. It seems daft. It does the trick.
- Whilst you are thinking about something else, this is an easy mistake to make — so tuck your phone away.
- A misfuel inhibitor helps, up to a point. Some diesels come with a filler designed to block a petrol nozzle, and add-on devices exist for motors without one. They are a safety net, not a reason to stop reading the pump.
- Stop as soon as you realise. Less petrol in the tank means a weaker mix. It does not change what to do next, which is still not to crank it.
Put petrol in a diesel around Brooklands already?
Then, there's only a short order of things. Leave it unstarted, with the ignition off as well. Ask the attendants to help you push it clear of the pump if you're still on the forecourt, whether that's Asda or somewhere else. What got in, about how much, and whether it's 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 different fault — Brooklands has a page just for it.
Why one petrol in a diesel job in Brooklands costs more than another
An honest single price does not exist here: four scenarios, four separate tasks. The scenario itself does most of the work of moving the cost. Where the car is counts too, and whether a van can safely reach it, after the proportion of petrol to what that tank holds.
Three queries come first, before quoting, rather than after — what got in, how much, has it run — and that is the reason. A range becomes a straight figure once the answers are in.
About Brooklands
Brooklands is a suburban area in Greater Manchester, situated on the riverside at an elevation of 28 metres, with semi-detached housing being the predominant type of accommodation. Brooklands is located near the cities of Salford and Manchester, and is close to nearby places such as Sale, Ashton upon Mersey, and Timperley. Brooklands has a population of approximately 6042 residents, and is about 160.8 miles northwest of London. Brooklands is characterized by its quiet, residential atmosphere, with the River Mersey flowing nearby.
Fuel drain cover around Brooklands and across Greater Manchester
Our vans answering petrol in diesel jobs in Brooklands, in the M postcode area, equally work the places near it, Sale, Ashton upon Mersey and Timperley among them. A forecourt, a supermarket car park, a lay-by or your own drive are all places we drain, and your car doesn't need to come to us.
At the petrol pump around Brooklands, right now?
Then you are in the best place there is. Ring, and leave it turned off.