Should You Worry? Petrol in a Diesel Car in Fulham
Provided it has not been started, worry less than you likely are. Till your ignition primes your pump, your starter turns, or the vehicle is driven, petrol in a diesel tank simply waits there and does no harm. Which means the truthful reply to that first Fulham query — "have I ruined it?" — normally no. Petrol in Diesel is who to call, with the motor left off, and so it remains that way. Keep reading for three things: the effect petrol has inside a diesel engine, the clues of how far it has spread, and ways to make sure you don't do it again.
What petrol in a diesel does to the engine
On its way through a motor, diesel has two jobs. It combusts, and before it burns it protects. Designed to very fine clearances, your injectors and your pump depend on your diesel flowing through them to stop their surfaces wearing against one another.
Of those two tasks, petrol manages the first badly and the second not at all. Being less viscous than diesel, petrol strips out the protection a fuel system needs, leaving a pump running on the blend wearing itself. It's also made to resist igniting under compression — the opposite of what a diesel needs — which is why you hear the rattling.
Taken together, they make clear what shape the issue takes. Not contact but circulation is what does the damage. Petrol in a tank is a fuel problem. The start of a mechanical one is a pump that has been labouring on that petrol — and whatever a worn pump sheds travels on with the fuel to the fuel injectors downstream.
How bad is petrol in a diesel? Four situations we see around Fulham
Filled but not once started — as good as it gets. Only that tank has petrol in it, and so the job is clearing that tank and purging your system where your car stands. 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 your system primed, your lines and filter now hold petrol that has come from the tank. Usually nothing more than clearing, flushing and seeing to the filter, so still straightforward.
A couple of miles driven, and the pump has spent every one of them working on weakened fuel. Miles is only half of it; how hard it was driven counts just as much. Either way this work includes your tank, the fuel lines, your filter and clean fuel through the entire circuit. Short trips, such as the school run to All Saints CofE Primary School, are one matter. Any miles on the M4, under 5 miles from Fulham, means the engine has worked hard throughout, and a run to Westminster, under 5 miles away, is a very different task as well.
Driven on until it protested — knocking, smoke, an uneven idle, a dead throttle. 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 Fulham Palace Road. A car stopped quickly very seldom has permanent damage, since the fuel drain and the flush, which still come first, take care of it.
What Fulham drivers get told about petrol in a diesel — and the stories in it
Myth: topping up to full with diesel makes it fine. It doesn't. Nothing is removed when you top up — the tank simply holds more of the same blend. A diesel fuel system doesn't tolerate petrol by percentage in the way that guidance presumes.
"Current diesels can handle a little petrol" — a myth, and nearer the reverse. A modern diesel runs its fuel through finer parts at higher pressure, which makes the lubrication matter more, not less.
This is the one that fools motorists. Myth: "If it starts and drives, there is no damage done." The driver of a petrol motor fed diesel usually stops, since it will not run, and the harm stops with them. While your pump wears, a diesel fed petrol normally starts, idles and drives away as though nothing has happened. Being able to run isn't proof of being fine.
Myth: a two-stroke additive makes it safe to drive home. It is an old fix, supposed for another problem. It does not put back what petrol has diluted, and the petrol is still in your tank later.
The next start sends petrol back round the pump from the fuel lines and the fuel filter, where some of that ends up after the engine has been run. That is why a DIY tank drain doesn't leave you sorted — a myth. Clearing petrol into a can by the kerbside is also truly risky.
How does petrol in a diesel occur?
A careless moment is seldom the cause, and nobody means to do it. The forecourt makes it simple: the petrol nozzle is the smaller of the two, and it slides into a diesel filler with almost no resistance, whilst a diesel nozzle generally won't go into a petrol car at all. So the slip runs one way.
The moment routine stops matching the car is the moment it occurs. 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, only with its pumps arranged differently. A rushed fill en route to Putney with a train to catch. Years of petrol motors behind you, a diesel Renault Megane in front of you on the forecourt for its first tank — that is when. With rain, a call arriving, or children to deal with, the hand simply does what it has always done.
Preventing petrol in a diesel next time you fill up in Fulham
- Not every forecourt in the UK follows green for unleaded and black for diesel, though most usually do. Check the pump's label; the colour is just a clue.
- Many motors state the fuel type inside the filler flap or on the cap, and so check it on the first fill in a car you don't know.
- A coloured fob or a sticker on your diesel's key achieves more than any amount of intending to remember, for a household with one of each.
- Before the nozzle comes off the pump the first time you fuel a hired or new vehicle, say "diesel" out loud. Silly, perhaps, yet it works.
- Thinking about something else is when this becomes an easy mistake to make, so tuck your phone away and keep your mind on the pump.
- Some diesels have a filler built to block a petrol nozzle, and devices you can add exist for motors 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 realise. Less petrol inside your tank makes a weaker mix. It doesn't change what to do next, which is still not to fire it up.
Put petrol in a diesel in Fulham already?
In that case, there's just a short order of things. Leave it unstarted, with your ignition switched off as well. Ask the staff to help you roll it away from the pump if you are still on the forecourt, whether that is Sainsbury's or anywhere else. Next, 0333 366 0103. We'll ask what went in, about how much, and if it has been run.
If it was AdBlue rather than petrol, say so. That is a different problem — corrosion and deposits rather than lost protection — and it has its own page for Fulham.
What makes one Fulham petrol in a diesel job cost more than the next
The four scenarios above are four separate jobs, so no single price for this would be fair. The situation itself does most of the work of moving your cost. After that it is the share — how much petrol was put in against how much your tank takes — and then where the car is and whether our van can get to it safely.
That is why our technicians ask three queries before pricing rather than after: what was put in, how much, and if it's run. Given the answers, you get a straight figure rather than a range.
About Fulham, briefly
Fulham is a locality in southwest London, situated on the north bank of the River Thames at an elevation of around 9 metres. Fulham lies close to several neighbouring areas, including Parsons Green, Putney, and Walham Green, and is approximately 4.4 miles from central London. Fulham is predominantly composed of flat dwellings, housing a population of around 8018 residents. Fulham's riverside setting has influenced its development and character over time.
Across Greater London and around Fulham: fuel drain cover
Petrol in diesel call-outs around Fulham — part of the SW postcode area — go to vans that also cover the locations around it, Parsons Green, Putney and Walham Green among them. A forecourt, a supermarket car park, a lay-by or your own driveway are all locations our technicians drain, and the vehicle doesn't need to move to us.
In Fulham and still at the petrol pump?
Then you're in the best position there is. Keep it off. Call.