Coltness: Petrol in a Diesel Car? How Worried to Be
Likely less than you are now — provided no one has started the car. Until the ignition primes the pump, your starter cranks, or your car is driven, petrol in a diesel tank simply waits there and does nothing. Which means the truthful reply to that first Coltness question — "have I wrecked it?" — usually no. Leave your motor off and ring Petrol in Diesel — that keeps it that way. Further down, you will find what petrol really does inside a diesel, how far it might have got, and how to stop it happening to you a second time.
Petrol in a diesel: what does it do to the engine?
Diesel does two jobs on its way through a motor. It ignites, and before it ignites it lubricates. What keeps the surfaces inside your high-pressure pump and the fuel injectors from wearing against each other is the diesel flowing through them — they are designed to extremely fine clearances.
Poorly at the first, not at all at the second: that's petrol. A pump running on a petrol blend is wearing itself out, because petrol is thinner than diesel and strips out the lubrication 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's where the knocking comes.
Put those together and the shape of the trouble is plain. Contact doesn't do the damage — movement does. Petrol in a tank is a fuel fault. Whatever a worn pump sheds travels on, borne by your fuel, into the injectors further along, which is why a pump that has worked on the petrol is where a mechanical issue begins.
Four scenarios our engineers see around Coltness: how serious is petrol in a diesel?
Filled up, not once started. The best case there is. Being at a forecourt is what makes this the case: elsewhere, the car has been driven there to begin with. With the petrol held inside your tank alone, it is cleared and flushed on the spot, and nothing more is needed.
Started for a second, or only your ignition on. The system has been primed, so petrol has left your tank and reached the filter and the fuel lines. Still generally straightforward: drain, flush, and the filter dealt with.
Driven a couple of miles. Now the pump has spent those miles working on weakened fuel. The work is the tank, the lines, your filter and clean fuel through the whole system, and how hard the vehicle was driven matters as much as how far. On the school run to the local primary school, the mileage is small. Very different again: a trip to Glasgow, under 15 miles away, or any distance on the M74, under 5 miles from Coltness, where the motor never stopped labouring hard.
Rattling, an uneven idle, smoke, a throttle gone soft: driven till it complained. What you are hearing is the motor signalling fuel that no longer acts like diesel. Stop wherever you are — the verge on Kelso Crescent, a lay-by, a side street — and leave the vehicle there. What goes first is still the drain and flush, and that sorts it out, with lasting damage very uncommon if a car is pulled over soon.
Petrol in a diesel myths Coltness motorists hear
"Top it up the rest of the way with diesel and it'll be fine" — a myth. It will not. Nothing comes out when you top up — the tank simply carries more of the same blend. That advice presumes a diesel fuel system tolerates petrol by percentage. It does not.
Not so: a current diesel copes with a bit of petrol. Rather, the reverse. A modern diesel sends its fuel through finer components at higher pressure, which makes the protection matter more, not less.
The myth that catches motorists off guard: if it starts and drives, it must be unharmed. Feed diesel to a petrol engine and it generally won't run, and so the driver stops — and the harm stops with them. While your pump grinds, a diesel fed petrol usually starts, idles and drives away as though nothing has happened. Being able to run is not the same as being fine.
"A drop of two-stroke oil and drive it home" — a myth, taken from a fix from years ago, for a different issue. That petrol is still in the tank afterwards, and whatever it has weakened is not put back.
"Drain it yourself and you are sorted" — a myth, because after it's been running some petrol sits in your filter and lines, waiting to go straight back through the pump at your next start. It is also genuinely risky to drain petrol into a can at the kerbside.
Why petrol in a diesel occurs so easily
On purpose? Never. Through carelessness? Rarely, if ever. The forecourt makes it easy: the petrol nozzle is the narrower 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 motor at all. So the error runs one way.
The moment routine stops matching the car is the moment it occurs. Courtesy car, hire car, or a vehicle that is brand new. Households running one of each, petrol and diesel. The pumps in a different order on a well-known forecourt. Racing for a train at Cleland 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's when. Throw in rain, a phone call or a back seat full of kids, and your hand repeats what it has always done.
Avoiding petrol in a diesel next time you fill up around Coltness
- Check the pump, not the colour. In the UK unleaded handles are generally green and diesel black, yet not on every forecourt. The label is what counts.
- The first fill in an unfamiliar vehicle is the time to check your filler flap — inside it, or on the cap, plenty of vehicles state the fuel they take.
- A coloured fob or a sticker on your diesel's key achieves more than any amount of meaning to remember, in a home with one of each.
- "Diesel", out loud, before you pick up the nozzle — every time a new or hired car needs its first tank. It seems silly. It works.
- Thinking about something else is when this becomes an easy mistake to make, and so put your phone away then keep your mind on the petrol pump.
- Add-on devices are available for cars without one, and some diesels are built with a filler that will not take a petrol nozzle. Helpful — but a backstop only, never a reason to stop checking the label.
- Stop as soon as you notice. Less petrol in your tank means a thinner mix. It doesn't change what to do next, which is still not to fire it up.
Coltness: already put petrol in a diesel?
Short and simple, then, is the order of things. Do not start it, and do not turn the ignition on. The attendants at the forecourt — whether at Morrisons itself or wherever you filled up — will normally help roll it clear of the pump if you ask. Call 0333 366 0103 next, with three answers — the fuel, the approximate quantity, and whether it's run.
Corrosion and deposits are the problem with AdBlue, whereas petrol brings lost protection. So if it was AdBlue, say so — and see its own Coltness page.
Coltness petrol in a diesel tasks: why one costs more than another
A fair single quote does not exist here: four situations, four separate jobs. What shifts the cost is chiefly which of them you're in. Where the vehicle is matters too, and whether a technician can safely reach it, after the ratio of petrol to what that tank holds.
Three questions come first, before quoting, instead of after — what went in, how much, has it run — and this is the reason. Those answers turn a range into a straight figure.
About Coltness itself
Coltness is a suburban area situated on the riverside in North Lanarkshire, with a mix of terraced housing and local amenities. Coltness sits at an elevation of 144 metres, close to the nearby towns of Wishaw and Cleland. Coltness is located near the larger town of West Crindledyke and is approximately 13.5 miles from Glasgow. Coltness has a population of around 4662 residents.
Across North Lanarkshire and in Coltness: fuel drain cover
Petrol in diesel calls around Coltness — part of the ML postcode area — go to vans that also cover the spots round it, Wishaw, Cleland and West Crindledyke included. Our engineers 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.
Still at the petrol pump around Coltness?
The best spot there is, then — that is where you are. Leave the car turned off, then ring.