How Worried Should You Be? Petrol in a Diesel Car in Preston
Unstarted? Then less worried than you likely are. "Have I ruined it?" is the first thing everyone around Preston asks, and the honest answer is normally no, because petrol left in a diesel tank hurts nothing till it's dragged through the system — by ignition priming, by the starter, or by driving. Keep it that way: leave the engine off then call Petrol in Diesel. Further down, you will find what petrol really does inside a diesel, how far it may have gone, and how to stop it happening to you a second time.
Inside the engine: what petrol in a diesel really does
Passing through a motor, diesel does two jobs at once. Lubricating comes before burning; it does both. Designed to very fine gaps, the injectors and your pump depend on your diesel moving through them to keep their surfaces from wearing against one another.
Petrol does the first task poorly and the second not at all. A pump working on a petrol mixture is wearing itself out, because petrol is thinner 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 rattling comes.
The shape of the problem is plain once you put those together. Not contact but circulation is what causes the harm. Petrol in the tank is a fuel issue. After the pump has been running on that petrol, a mechanical fault has begun: whatever is shed by a pump that's wearing travels onward to the injectors with your fuel.
Four situations we see in Preston: how bad is petrol in a diesel?
Fuelled up, never started. The best case there is. At a forecourt, and really only there, the petrol is still limited to your tank — because anywhere else your car was driven to get to it. The job is draining and rinsing on the spot.
Started for a moment, or only the ignition on. Once primed, the fuel system has drawn petrol from the tank up to the filter and the fuel lines. That's generally still an easy job — a drain, a flush, and your filter seen to.
Some miles driven, and the pump has spent every one of them working on diluted fuel. The work is that tank, the fuel lines, the fuel filter and clean fuel through the entire circuit, and how hard the vehicle was driven counts as much as how far. Driving the kids to Preston Primary School is one sort of trip. Very different a second time: a run to Canterbury, under 10 miles away, or any mileage on the M2, under 15 miles from Preston, where the engine kept labouring hard.
Driven till it complained. Knocking, a ragged idle, smoke, a throttle that has gone soft. That is the engine telling you its fuel has stopped acting like diesel. Whether it's the verge on The Downs, a lay-by or a side road, stop where you are and leave it. What comes first is still the drain and flush, and that deals with it, with long-term damage very rare when a vehicle is stopped soon.
What Preston motorists get told about petrol in a diesel — and the myths in it
False: topping up to full with diesel makes it fine. It does not. Nothing is removed by topping up — you are left with a bigger tank, still the same mixture. That advice assumes a diesel fuel system handles petrol by percentage. It doesn't.
Myth: a newer diesel copes with a bit of petrol. If anything, the reverse. Protection counts more on current diesels, not less, because their fuel passes through more precise parts at higher pressure.
The myth that catches motorists out: if it starts and drives, it must be unharmed. Feed diesel to a petrol engine and it normally won't run, and so the driver stops — and the damage stops with them. Nothing looks to have happened when a diesel fed petrol fires up, ticks over and drives away, which it usually does; meanwhile the pump grinds. Being able to run isn't proof of being fine.
"A drop of two-stroke oil and drive it home" — a myth, taken from a fix from years ago, for a distinct fault. It doesn't put back what petrol has thinned, and the petrol is still in your tank after that.
The next start draws petrol back round your pump from your lines and your filter, where some of it sits once the engine has been run. That is why a DIY tank drain doesn't sort it — a myth. Clearing petrol into a can by the roadside is also really hazardous.
Why petrol in a diesel occurs at all
A careless moment is rarely the cause, and nobody means to do it. The forecourt makes it simple: the petrol nozzle is the smaller of the two, and it slips into a diesel filler with almost no resistance, whilst a diesel nozzle generally won't go into a petrol vehicle at all. So the slip runs one way.
It takes place when habit and the car stop matching. Any car that is new to you — hired, on loan as a courtesy car, or just bought. One petrol and one diesel on the driveway of the same household. A forecourt you know, but with its pumps arranged differently. Racing for a train at Minster and fuelling up en route. Years of petrol cars behind you, a diesel Renault Megane in front of you at the forecourt for its first tank — that is when. Your hand repeats what it has always done once you add rain, a phone call or a back seat full of children.
How to prevent petrol in a diesel on your next fill-up around Preston
- Read the petrol pump, not the colour. In the UK unleaded handles are normally green and diesel black, but not on each forecourt. The label is what matters.
- Inspect the filler flap. Many motors state the fuel type inside the flap or on the cap. Look at it on the first fill in a vehicle you do not know.
- A coloured fob or a sticker on the diesel's key achieves more than any amount of meaning to remember, for a household with one of each.
- Say it before you lift it. On your first fill in a new or hired car, say "diesel" aloud before you take the nozzle off the petrol pump. It sounds silly and it does the trick.
- Thinking about something else is when this becomes an easy mistake to make, and so tuck your phone away and keep your mind on the pump.
- Add-on devices are available for vehicles without one, and some diesels are built with a filler that will not take a petrol nozzle. Useful — but a backstop only, never a reason to stop checking the label.
- Less petrol means a thinner mix, so stop the moment you notice — while remembering that the next step is unchanged. It is still not to start the vehicle.
Petrol already in a diesel around Preston? Start here
In that case, there is just a short order of things. Starting it is out, and so is switching on the ignition. Ask the staff to help you roll it away from the petrol pump if you're still on the forecourt, whether that's Shell or somewhere else. Next, 0333 366 0103. We'll ask what went in, about how much, and if it's been run.
If it was AdBlue and not petrol, say so. That is a separate issue — corrosion and deposits rather than lost protection — and it has its own page for Preston.
One petrol in a diesel task in Preston costs more than another. Why?
An honest single price does not exist here: four situations, four separate tasks. Mostly, the cost moves with which situation you are in. Beyond that it's the proportion — how much petrol went in against how much that tank takes — and after that where your car is and whether a technician can reach it safely.
Three queries come first, before any quote, instead of after — what got in, how much, has it run — and this is the reason. With the replies, you get a straight figure instead of a range.
About Preston, briefly
Preston is a small village in Kent, situated inland at an elevation of around 15 metres, and is located approximately 6.6 miles from Canterbury. Preston has a population of around 587 people and is characterised by predominantly detached housing. Preston is part of a network of rural villages and hamlets, including nearby Elmstone, Grove, and Perry, in the South East of England. Preston is also within commuting distance of London, being around 60 miles from the capital.
Across Kent and around Preston: fuel drain cover
Preston rests in the CT postcode area, and the teams that answer petrol in diesel jobs there work the locations near it as well — Elmstone, Grove and Perry among them. The vehicle doesn't need to move to us: our technicians drain on a forecourt, in a supermarket car park, in a lay-by or on your own drive.
Still at the petrol pump in Preston?
Then you are in the best place there can be. Leave the car switched off, then ring.