How Worried Should You Be? Petrol in a Diesel Car in Fivecrosses
Probably less than you already are — provided no one has started the car. Petrol sitting in a diesel tank does nothing to the motor till something draws it through the fuel system — the ignition priming your pump, the starter, or driving itself. So the truthful answer to the first query everyone around Fivecrosses asks, "have I ruined it?", is generally no. Leave your motor off and phone Petrol in Diesel — that keeps it like that. The remainder of this page explains what petrol actually does to a diesel, how to judge how far it has got, and how to make sure it doesn't happen to you a second time.
What petrol in a diesel does to your engine
Passing through an engine, diesel does two jobs at the same time. Lubricating comes before burning; it does both. What stops the surfaces inside the high-pressure pump and the injectors from wearing against each other is your diesel flowing through them — they are built to extremely fine clearances.
Of these two jobs, petrol manages the first poorly and the second not at all. It's runnier than diesel and takes away the protection the fuel system depends on, so a pump running on a petrol mix is a pump wearing itself. And petrol is made to resist igniting under compression, which is the reverse of what a diesel needs from its fuel. That is where the clattering comes from.
Together, those make the shape of the trouble clear. Contact does not do the damage — circulation does. Petrol in the tank is a fuel fault. The beginning of a mechanical one is a pump that has been labouring on that petrol — and whatever a worn pump sheds travels on with your fuel to your injectors beyond it.
Fivecrosses, petrol in a diesel: four cases, from mild to serious
The best case there is: filled up, never started. That petrol is inside your tank and just the tank, and the job is a drain and a flush where the car stands. This is the one situation that can only really occur at a forecourt, as anywhere else the vehicle has been driven to get there.
Ignition on, or started for a second. Petrol has left the tank and got to the filter and the fuel lines, since your system has been primed. Drain, flush, see to the fuel filter: still normally simple.
Driven a couple of miles. Now your pump has spent those miles running on weakened fuel. Tank, lines, filter, then fresh fuel run through the entire circuit: that is the work, and the way the vehicle was driven matters as much as the mileage. A school run to Frodsham CofE Primary School is one matter. Very different once more: a trip to Chester, under 10 miles away, or some mileage on the M56, under 3 miles from Fivecrosses, where the motor never stopped labouring hard.
Driven until it complained. Rattling, an uneven idle, smoke, a throttle that has gone soft. What you are hearing is the engine reporting fuel that no longer acts like diesel. Stop on the spot — on the verge on Kingsley Road, at the kerb, down a side road — and don't move it again. What goes first is still the fuel drain and flush-through, and that sorts it out, with long-term damage very unusual if a car is stopped quickly.
Stories Fivecrosses drivers hear about petrol in a diesel
It will not be fine. The myth: "Fill it the rest of the way with diesel and it'll be." Nothing is removed by topping up — you are left with a fuller tank, still the same mixture. A diesel fuel system does not tolerate petrol by percentage in the way that guidance assumes.
Not so: a modern diesel copes with a bit of petrol. Rather, the opposite. More precise parts and higher pressure are how a newer diesel runs its fuel, and that makes the protection count more, not less.
Myth: "If it starts and drives, there is no harm done." This is the one that catches motorists. Any petrol motor fed diesel generally won't run, so the driver stops and the harm stops with them. Nothing seems to have happened when a diesel fed petrol fires up, ticks over and drives away, as it usually will; meanwhile your pump wears. A running engine doesn't mean fine.
An outdated workaround for a different issue lies behind this one. Myth: "Add some two-stroke oil and drive the vehicle home." What petrol has weakened stays weakened, and that petrol stays inside that tank regardless.
Myth: "Drain that tank yourself and you're sorted." Once your engine has run, some of the petrol is no longer inside your tank: it is in your filter and the lines, and it goes right back through your pump on the next start. On top of that, petrol emptied into a can by the road is genuinely dangerous.
Why petrol in a diesel occurs so easily
Nobody does it on purpose, and it is seldom carelessness. One way only, since of the nozzles: the smaller petrol one slides inside a diesel filler with almost no resistance, whereas the diesel one generally will not fit a petrol car. That's how the forecourt makes it simple.
Routine and the vehicle getting out of step is how it occurs. Courtesy car, hire car, or a motor that's new. One petrol and one diesel on the drive of the same household. Your usual forecourt, its pumps now in a different order. A hurried fill en route to Frodsham with a train to catch. Years of petrol vehicles behind you, a diesel Volkswagen Passat in front of you on the forecourt for its first tank — that's when. Add rain, a phone call or a back seat full of kids, and your hand repeats what it has always done.
How to avoid petrol in a diesel at your next fill-up in Fivecrosses
- The label is what matters, so read the pump rather than the colour: in the UK unleaded handles are usually green and diesel black, but not on every forecourt.
- In a motor you don't know, look inside the flap over the filler or at the cap before your first fill: many motors state the fuel there.
- One of each in the house? Label the key to the diesel — a coloured fob, a sticker — since meaning to remember is not enough.
- It seems daft and it does the trick: on the first fill in a new or hired car, say "diesel" aloud before you lift the nozzle off the petrol pump.
- Mistakes like this are simple to make while your mind is on something else, and so your phone goes away.
- Up to a point, a misfuel inhibitor helps: some diesels have a filler designed to block a petrol nozzle, and add-on devices are available for the remainder. Count it as a safety net, and keep checking the pump.
- Noticing it halfway? Stop at once. A weaker mixture results from less petrol in that tank, yet the next stage stays the same: don't fire it up.
Already put petrol in a diesel around Fivecrosses?
The order of things is brief, then. Leave it unstarted, with the ignition off too. Still at the forecourt, at Wharton Lake Garage or anywhere else? Ask the staff to help you roll it clear of the pump. Next, 0333 366 0103. We'll ask what was put in, roughly how much, and if it has been run.
If it was AdBlue instead of petrol, say so. That is a separate issue — corrosion and deposits and not lost protection — and it has its own page for Fivecrosses.
What makes one Fivecrosses petrol in a diesel job cost more than the next
Four separate tasks lie behind the four scenarios above — which is why there is no fair single quote. Mostly, your cost shifts with which situation you're in. Where your car is matters too, and whether a van can safely reach it, after the ratio of petrol to what your tank holds.
That's why our technicians ask three queries before pricing rather than after: what got in, how much, and whether it has run. A range turns into a straight figure once those replies are in.
About Fivecrosses
Fivecrosses is a small suburban area in Cheshire, situated near the coast and approximately 9.9 miles from Chester. Fivecrosses has a relatively low elevation of 99 metres and is characterised by detached housing. Fivecrosses is close to other nearby places such as Bradley, Overton, and Newton, and is about 163.8 miles from London.
Across Cheshire and around Fivecrosses: fuel drain cover
Petrol in diesel jobs around Fivecrosses — part of the WA postcode area — go to vans that likewise cover the spots round it, Bradley, Overton and Newton among them. Our engineers drain where the car is — your own drive, a lay-by, a supermarket car park, a forecourt — so it never needs to come to us.
At the petrol pump around Fivecrosses, still?
The best position there is, then — that is where you are. Keep it off. Phone.