Stowford: Petrol in a Diesel Car? How Worried to Be
Unstarted? Then less anxious than you probably feel. Everyone around Stowford begins with "have I wrecked it?", and the honest answer is usually no: petrol resting in your tank of a diesel stays harmless till priming, cranking or driving draws it into the fuel system. Leave the engine off then call Petrol in Diesel — that is how you keep it like that. Keep reading for three things: the effect petrol has inside a diesel motor, the signs of how far it has spread, and ways to make sure you never do it again.
What petrol in a diesel does to the motor
Passing through a motor, diesel is doing two jobs at the same time. Before it combusts, it lubricates — and then it combusts. Built to very fine clearances, the fuel injectors and your pump depend on the diesel moving through them to stop their surfaces wearing against one another.
Badly at the first, not at all at the second: that's petrol. Being less viscous than diesel, petrol strips out the protection a fuel system needs, so a pump running on the mixture to wear itself. It is also made to resist igniting under compression — the opposite of what a diesel needs — which is why you get the clattering.
Seen together, they show the shape the issue has. It is movement that does the damage, not contact. Where the petrol is only inside the tank, it is a problem of fuel, nothing more. Whatever a worn pump sheds travels on, borne by the fuel, into the fuel injectors further along, which is why a pump that has been working on that petrol is where a mechanical problem begins.
Four situations our engineers see around Stowford: how bad is petrol in a diesel?
Filled but not once started — the best it gets. At a forecourt, and genuinely only there, the petrol is still limited to that tank — because everywhere else the car was driven to reach it. The task is emptying and cleaning on the spot.
A moment's running, or merely the ignition on. With the fuel system primed, your lines and filter now contain petrol that came from your tank. Normally nothing more than emptying, cleaning and seeing to the filter, so still simple.
A few miles driven, and the pump has spent every one of them labouring on weakened fuel. Tank, lines, filter, then fresh fuel run through the entire circuit: that's the work, and the way the car was driven counts as much as the distance. On the school run to Sidmouth Church of England (VA) Primary School, the miles is short. Very different again: a trip to Exeter, under 15 miles away, or some distance on the M5, under 10 miles from Stowford, where the motor kept running hard.
Clattering, a ragged idle, smoke, a throttle gone soft: driven till it complained. The engine is telling you the fuel is no longer behaving like diesel. Leave it where it has stopped: a lay-by, a quiet street, the verge on Greenway Lane. What comes first is still the drain and flush-through, and that deals with it, with lasting damage very rare when a car is pulled over quickly.
Myths Stowford motorists hear about petrol in a diesel
Myth: topping up to full with diesel makes it fine. It does not. Topping up takes out nothing; it gives you a fuller tank of the same mixture. The idea behind that guidance — that diesel fuel systems accept petrol by percentage — is wrong.
"Newer diesels can handle a little petrol" — a myth, and closer to the opposite. Lubrication matters more on current diesels, not less, since their fuel passes through more precise components at higher pressure.
This is the one that catches drivers. Myth: "If it starts and drives, there's no harm done." A petrol motor fed diesel generally will not run, so the driver stops and the harm stops with them. Feed petrol to a diesel and it normally starts, idles and drives away as if nothing happened — all the while its pump wears. Running isn't the same as fine.
An outdated workaround for a separate issue lies behind this one. Myth: "Add some two-stroke oil and drive it home." That petrol is still inside the tank after that, and what it has diluted isn't put back.
Myth: "Drain the tank yourself and you're sorted." After the motor has run, some of the petrol is no longer in the tank: it is in the fuel filter and the lines, and it goes right back through your pump on the next start. On top of that, petrol cleared into a can by the road is truly dangerous.
Why petrol in a diesel takes place so easily
A careless moment is rarely the cause, and nobody means to do it. The petrol nozzle is the smaller of the two and slides into a diesel filler with almost no resistance; a diesel nozzle mostly will not go into a petrol car at all. The forecourt makes it simple, and the slip runs one way.
Routine and the car getting out of step is when it occurs. A new car, a hire car or a courtesy car. Two cars on one drive, one petrol, one diesel. Your ordinary forecourt, its pumps now in a different order. A train to catch, and a rushed fill on the way to Feniton. The first fill-up in a diesel Volkswagen Golf after years of driving petrol is exactly the moment it takes place. Add rain, a phone call or a back seat full of kids, and the hand does what it has always done.
Stowford motorists: how to prevent petrol in a diesel next time
- The label is what counts, so read the petrol pump instead of the colour: in the UK unleaded handles are usually green and diesel black, but not on each forecourt.
- Plenty of cars state the fuel inside the filler flap or on the cap, and so check it on your first fill in a car you do not know.
- One of each in the house? Mark your key to your diesel — a bright fob, a sticker — because intending to remember is not enough.
- Say it before you lift it. On the first fill in a new or hired car, say "diesel" aloud before you lift the nozzle off the pump. It seems silly and 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 vehicles without one, and some diesels come with a filler that will not accept a petrol nozzle. Helpful — but a backstop at best, never a reason to stop checking the label.
- Noticing it halfway? Stop at once. A thinner mix follows from less petrol inside that tank, but your next step stays the same: do not fire it up.
Already put petrol in a diesel around Stowford?
The order of things is short, then. Leave it unstarted, with the ignition off too. If you are still on the forecourt — the nearest petrol station or anywhere else — ask the attendants to help you push it away from the pump. Next, 0333 366 0103. We will ask what got in, roughly how much, and if it's been run.
Say so if it was AdBlue rather than petrol: it is a separate problem, with its own page for Stowford, because AdBlue brings corrosion and deposits rather than lost protection.
One petrol in a diesel task around Stowford costs more than another. Why?
A fair single quote does not exist here: four situations, four separate tasks. Chiefly, your cost shifts with which situation you're in. Where the car is counts too, and whether our van can safely reach it, after the proportion of petrol to what the tank holds.
What went in, how much, and whether it has run — three questions we ask before pricing, not after, for exactly that reason. Those answers are what change a range into one firm number.
About Stowford, briefly
Stowford is a small coastal hamlet in Devon, situated near the cities of Exeter and the surrounding villages of Higher Woolbrook, Bowd, and Middle Woolbrook. Stowford sits at an elevation of 65 metres, with detached housing being the predominant type of accommodation in the area. Stowford is located approximately 12 miles from Exeter and 147 miles from London, making it a rural community with some distance from major urban centres.
Stowford and Devon: where our fuel drain cover reaches
Higher Woolbrook, Bowd and Middle Woolbrook are among the spots near Stowford that the same vans work, answering petrol in diesel call-outs across Stowford's EX postcode area. We drain wherever your vehicle is — your own driveway, a lay-by, a supermarket car park, a forecourt — so it never needs to come to us.
Stowford: still at the pump?
In that case, you could not be in a better place. Call, and keep it turned off.