Should You Worry? Petrol in a Diesel Car in West Mains
Provided it has not been started, you can worry less than you likely are. Until the ignition primes the pump, the starter turns, or the vehicle is driven, petrol in a diesel tank simply rests there and does nothing. Which means the honest reply to that first West Mains query — "have I wrecked it?" — usually no. To leave it that way, ring Petrol in Diesel then leave the engine switched off. The remainder of this page covers what petrol really does to a diesel, how to judge how far it has got, and how to make sure it does not happen to you again.
What petrol in a diesel does to the engine
Passing through an engine, diesel is doing two things at the same time. It protects first, and after that does it burn. Designed to very fine gaps, the injectors and the pump rely on your diesel moving through them to keep their surfaces from wearing against one another.
Of those two jobs, petrol handles the first poorly and the second not at all. A pump running on a petrol mix is wearing itself out, because petrol is runnier than diesel and takes away the protection your fuel system relies on. Petrol is also made to resist igniting under compression — the reverse of what a diesel needs from its fuel — and that is where any knocking comes.
Together, those make the shape of the problem clear. Contact does not do the harm — circulation does. Petrol in the tank is a fuel issue. The start of a mechanical problem is a pump that has been labouring on that petrol — and whatever a worn pump sheds travels on with the fuel to the injectors beyond it.
West Mains, petrol in a diesel: four situations, from mild to significant
Fuelled, and not started: nothing beats it. Just your tank has petrol in it, so the job is emptying the tank and cleaning the fuel system where the car sits. This scenario can only truly occur on a forecourt: anywhere else, the vehicle got there by being driven.
Ignition on, or started for a second. With the fuel system primed, the lines and filter already contain petrol that has come from that tank. Drain, flush, deal with the fuel filter: still normally straightforward.
A few miles driven, and your pump has spent every one of them labouring on weakened fuel. How hard your car was driven matters as much as how far, and the work takes in the tank, the fuel lines, your filter and clean fuel through the entire circuit. A school run to the local primary school is one matter. Getting as far as Glasgow, under 10 miles away, makes a very different job — as does any miles on the M74, under 5 miles from West Mains, with your engine labouring hard all the way.
Driven on till it protested — knocking, smoke, a ragged idle, a soft throttle. The fuel isn't behaving like diesel any more, and the motor is saying so. Leave it wherever it has stopped: a lay-by, a quiet street, the verge on Cornwall Street. The fuel drain and flush-through still go first, and they deal with it: if a vehicle is pulled over soon, lasting damage is very unusual.
What West Mains drivers get told about petrol in a diesel — and the myths in it
"Top it up the rest of the way with diesel and it will be fine" — a myth. It won't. Topping up removes nothing; it gives you a fuller tank of the same mixture. Percentage is not how a diesel fuel system tolerates petrol, whatever that advice presumes.
Not so: a newer diesel copes with a bit of petrol. Rather, the opposite. At higher pressure, through finer components: that's how a modern diesel handles its fuel, so the protection matters more, not less.
One myth that catches people off guard: if it starts and drives, it must be unharmed. Feed diesel to a petrol engine and it normally will not run, so the motorist stops — and the harm stops with them. While your pump grinds, a diesel fed petrol normally starts, ticks over and drives away as though nothing has happened. Running does not mean fine.
An outdated fix for a different issue is behind this one. Myth: "Add some two-stroke oil and drive the vehicle home." What petrol has weakened remains weakened, and that petrol stays inside your tank anyway.
"Drain it yourself and you're sorted" — a myth, since after it has been running some petrol sits in your filter and lines, ready to go straight back through your pump at the next start. Emptying petrol into a can at the roadside is also genuinely hazardous.
Why petrol in a diesel happens at all
A careless moment is rarely the cause, and no one means to do it. The petrol nozzle is the smaller of the two and slips into a diesel filler with almost no resistance; a diesel nozzle mostly will not go into a petrol vehicle at all. The forecourt makes it easy, and the slip runs one way.
When habit and your car stop matching, it takes place. Hire cars, courtesy cars, and vehicles that are new to you. Households running one of each, petrol and diesel. A forecourt you know, but with its pumps arranged differently. A rushed fill en route to East Kilbride with a train to catch. Exactly the moment it occurs: after years of driving petrol, someone fills a diesel Renault Clio 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 children.
Next time you fill up around West Mains: avoiding petrol in a diesel
- The label is what counts, so read the petrol pump instead of the colour: in the UK unleaded handles are usually green and diesel black, yet not on each forecourt.
- Inspect your filler flap. Plenty of motors state the fuel type inside the flap or on the cap. Look at it on the first fill in a motor you don't know.
- Good intentions count for less than a sticker or a fob in a bright colour on your diesel's key if a house has one of each. So label it.
- Before the nozzle leaves the pump the first time you fill a hired or new motor, say "diesel" aloud. Silly, yes, yet it works.
- Thinking about something else is when this becomes an easy mistake to make, and so tuck your phone away then keep your mind on the petrol pump.
- Up to a point, a misfuel inhibitor helps: some diesels come with a filler designed to block a petrol nozzle, and aftermarket devices exist for the rest. Count it as a safety net, and keep checking the pump.
- Stop the moment you realise. Less petrol inside the tank means a weaker mixture. It doesn't change what to do next, which is still not to crank it.
Already put petrol in a diesel around West Mains?
Short and simple, then, is the order of things. Do not switch the ignition on, and do not crank it. Ask the attendants to help you push it away from the pump if you're still at the forecourt, whether that's BP or somewhere else. Call 0333 366 0103 next, with three answers — the fuel, the rough volume, and whether it's run.
If it was AdBlue and not petrol, say so. That's a different issue — corrosion and deposits and not lost protection — and it has its own page for West Mains.
What makes one West Mains petrol in a diesel task cost more than the next
There is no fair single price for this, since the four situations above are four separate tasks. Chiefly, your cost shifts with which one you're in. The proportion counts next, meaning how much of the tank is petrol, and then the location of your car and whether reaching it is safe for our van.
What was put in, how much, and whether it's run — three questions our technicians ask before costing, not after, for exactly that reason. The replies change a range into a straight figure.
About West Mains itself
West Mains is a suburban area situated on the riverside in South Lanarkshire, with a mix of flat housing and local amenities. West Mains sits near the city of Glasgow, approximately 7 miles from the city centre, and is close to nearby places such as Birniehill and East Kilbride. West Mains has a population of around 5447 people and is located at an elevation of 191 metres. West Mains is also relatively distant from London, at around 337 miles away.
Fuel drain cover around West Mains and across South Lanarkshire
Petrol in diesel call-outs around West Mains — part of the G postcode area — go to vans that also cover the spots around it, Birniehill, The Murray and East Kilbride included. We drain wherever the vehicle is — your own drive, a lay-by, a supermarket car park, a forecourt — so it does not have to come to us.
West Mains: still at the petrol pump?
Then, you couldn't be in a better spot. Leave it switched off, then ring.