Soham: Petrol in a Diesel Car? How Worried to Be
Far less than you probably are, if it hasn't been started. Until the ignition primes the pump, your starter turns, or your vehicle is driven, petrol in a diesel tank simply waits there and does no harm. Which means the truthful reply to the first Soham query — "have I ruined it?" — normally no. To keep it that way, call Petrol in Diesel and leave your motor alone. What petrol actually does to a diesel, how to gauge how far it's travelled, and how to stop it from happening again: that is the rest of this page.
Petrol in a diesel: what does it do to the engine?
Two jobs fall to diesel on its route through a motor. Before it burns, it lubricates — and then it combusts. Extremely fine tolerances are built into the fuel injectors and the high-pressure pump, and just the diesel flowing through stops their surfaces grinding together.
Petrol handles the first task poorly and the second not at all. A pump working on a petrol blend is wearing itself out, because petrol is runnier than diesel and strips out the protection your fuel system relies on. Petrol is also designed to resist igniting under compression — the opposite of what a diesel wants from its fuel — and that is where any rattling starts.
The shape of the problem is clear once you put those together. Contact doesn't do the damage — movement does. Where that petrol is only inside that tank, it is an issue of fuel, nothing more. A pump that has been working on that petrol is the start of a mechanical one, and whatever a worn pump sheds moves on with the fuel to the injectors downstream.
How bad is petrol in a diesel? Four scenarios we see in Soham
Filled up, not once started. The best case there is. Being at a forecourt is what makes this possible: elsewhere, the car has been driven there to begin with. With that petrol kept in that tank alone, it's cleared and flushed on the spot, and nothing more is needed.
The ignition switched on, or a brief start. Petrol has left your tank and got to your filter and the fuel lines, because the system has been bled. Drain, flush, deal with your filter: still normally simple.
Driven a few miles. Now your pump has spent these miles running on weakened fuel. Tank, lines, filter, then clean fuel run through the whole circuit: that is the work, and the way the vehicle was driven counts as much as the miles. Driving the children to St Andrew's CofE Primary School is one sort of trip. Getting as far as Ely, under 10 miles away, makes a very different task — as does any miles on the M11, under 15 miles from Soham, with the engine running hard all the way.
Driven until it protested. Knocking, a lumpy idle, smoke, a throttle that has gone soft. The fuel isn't behaving like diesel any more, and the motor is saying so. Stop wherever you are — the verge on High Street, a lay-by, a side street — and leave the vehicle there. A car stopped soon very rarely has lasting damage, since the drain and the flush-through, which still go first, sort it out.
Soham drivers and the petrol in a diesel myths they hear
Myth: topping up to full with diesel makes it fine. It does not. Nothing comes out when you top up — the tank just carries more of the same mixture. That guidance presumes a diesel fuel system handles petrol by percentage. It doesn't.
Myth: a current diesel copes with a bit of petrol. Rather, the opposite. Lubrication counts more on modern diesels, not less, since their fuel passes through finer parts at higher pressure.
This is the one that fools drivers. Myth: "If it starts and drives, there's no damage done." Any petrol motor fed diesel usually will not run, and so the driver stops and the damage stops with them. Feed petrol to a diesel and it usually fires up, idles and drives away like nothing has happened — all the while its pump wears. Running doesn't mean fine.
"A drop of two-stroke oil and drive it home" — a myth, taken from a fix from years ago, for a distinct issue. It doesn't put back what petrol has diluted, and the petrol is still inside your tank after that.
"Drain it yourself and you are sorted" — a myth, because after it has been running some petrol lies in your filter and lines, waiting to go right back through the pump on the next start. And, a can of petrol filled by the kerbside is truly hazardous.
Petrol in a diesel: how does it take place?
Carelessness is rarely the cause, and no one means to do it. A diesel nozzle mostly won't fit a petrol car, but the smaller petrol nozzle goes into the filler of a diesel almost without resistance — so forecourts make this one error straightforward, and only in that direction.
It occurs when routine and your car stop matching. Hire cars, courtesy cars, and vehicles that are new to you. Households running one of each, petrol and diesel. A well-known forecourt with the pumps in a different order. Racing for a train outside the nearest station and fuelling up en route. The first fill-up in a diesel Volkswagen Golf after years of driving petrol is exactly the moment it takes place. With rain, a call coming in, or children to deal with, your hand simply does what it has always done.
Next time you fill up around Soham: preventing petrol in a diesel
- The label is what matters, and so read the pump rather than the colour: in the UK unleaded handles are usually green and diesel black, but not on every forecourt.
- Many vehicles state the fuel inside your filler flap or on the cap, and so check there on the first fill in any car you don't know.
- One of each in the home? Mark the key to the diesel — a coloured fob, a sticker — since intending to remember isn't enough.
- Before the nozzle leaves the petrol pump the first time you fill a hired or new car, say "diesel" out loud. Silly, perhaps, yet it does the trick.
- While you're 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 come with a filler that won't accept a petrol nozzle. Useful — but a backstop only, never a reason to stop checking the label.
- Less petrol makes a thinner mix, and so stop the moment you notice — while remembering that your next stage is unchanged. It's still not to crank it.
Put petrol in a diesel around Soham already?
The order of things is brief, then. Do not switch the ignition on, and do not fire it up. Yet at the forecourt, at Esso or anywhere else? Ask the staff to help you push the vehicle away from the pump. Ring 0333 366 0103 next, with three facts — your fuel, the rough quantity, and whether it has run.
If it was AdBlue rather than petrol, say so. That is a separate issue — corrosion and deposits instead of lost lubrication — and it has its own page for Soham.
What makes one Soham petrol in a diesel job cost more than the next
Four separate tasks sit behind the four scenarios above — which is why there is no honest single price. Mostly, your cost shifts with which one you are in. Next it's the share — how much petrol went in against how much that tank takes — and then where your car is and whether a technician can reach it safely.
What was put in, how much, and if it's run — three questions our engineers ask before quoting, not after, for precisely that reason. With the answers, you get a straight figure instead of a range.
About Soham
Soham is a town in eastern Cambridgeshire, situated on the banks of the River Great Ouse at a low elevation of around 8 metres. Soham lies near the city of Ely and is surrounded by areas such as East Fen Common, Down Field, and North Field. Soham has a population of approximately 9542 people, predominantly living in semi-detached housing. Soham is located about 60 miles from London, making it a commuter town with easy access to the capital.
Across Cambridgeshire and in Soham: fuel drain cover
Our teams answering petrol in diesel calls around Soham, in the CB postcode area, equally work the places near it, East Fen Common, Down Field and North Field among them. Our engineers drain wherever the car is — your own drive, a lay-by, a supermarket car park, a forecourt — so it does not have to come to us.
In Soham and still at the petrol pump?
In that case, you couldn't be in a better position. Keep it off. Ring.