Vicarage Row: Petrol in a Diesel Car? How Worried to Be
If it hasn't been started, you can worry far less than you probably are. Till the ignition primes the pump, the starter cranks, or the vehicle is driven, petrol in a diesel tank simply sits there and does no harm. Which makes the honest reply to the first Vicarage Row query — "have I ruined it?" — usually no. To keep it like that, call Petrol in Diesel and leave your engine switched off. The remainder of this page covers what petrol really does to a diesel, how to judge how far it has got, and how to make sure it does not happen to you again.
The motor and petrol in a diesel: what goes on
On its way through a motor, diesel does two jobs. Before it burns, it protects — then it combusts. What stops the surfaces inside the high-pressure fuel pump and the injectors from wearing down against one another is your diesel flowing through them — they're built to very fine clearances.
The second job petrol does not do at all, and the first it does badly. The knocking comes from petrol being made not to ignite when compressed, which is precisely the opposite of what a diesel needs. On top of that it is thinner than diesel, it strips out the lubrication your system depends on, and any pump working on such a blend is wearing itself.
Seen together, they make clear the shape the trouble takes. The damage is done by movement, not by contact. Petrol in a tank is a fuel issue. A pump that has been running on that petrol is the beginning of a mechanical one, and whatever a worn pump sheds travels on with your fuel to the fuel injectors further on.
Vicarage Row, petrol in a diesel: four situations, from mild to significant
The best case there can be: filled up, never started. At a forecourt, and truly only there, the petrol is still limited to your tank — since everywhere else your car was driven to reach it. The job is draining and cleaning on the spot.
Ignition on, or started for a second. Petrol has come out of your tank and got to your filter and the lines, since the system has been primed. Normally little more than emptying, cleaning and seeing to the filter, and so still easy.
Those few miles on the road meant the pump working on fuel diluted by petrol the whole way. How hard the car was driven counts as much as how far, and the work takes in your tank, the fuel lines, the fuel filter and clean fuel through the whole system. Driving the children to King's Academy Northern Parade (Junior) is one sort of trip. A run as far as Portsmouth, under 3 miles away, is a very different job. So is any distance on the M27, under a mile from Vicarage Row, where the motor has been running hard throughout.
Driven on till it protested — clattering, smoke, an uneven idle, a soft throttle. What you are hearing is the motor signalling fuel that no longer behaves like diesel. Leave it where it stops: a lay-by, a quiet street, the verge on Northern Parade. The fuel drain and flush-through still come first, and they sort it out: if a car is stopped soon, long-term damage is very rare.
Vicarage Row drivers and that petrol in a diesel myths they hear
False: topping up to full with diesel makes it fine. It does not. Nothing is removed by topping up — you're left with a fuller tank, still the same mixture. Percentage is not how a diesel fuel system tolerates petrol, whatever that advice presumes.
Not so: a newer diesel copes with a bit of petrol. If anything, the opposite. A modern diesel sends its fuel through finer components at higher pressure, which makes the lubrication count more, not less.
The myth that catches drivers out: if it starts and drives, it must be unharmed. Diesel in a petrol motor generally means a motor that will not run: the motorist stops, and so does the damage. Nothing looks to have happened when a diesel fed petrol fires up, ticks over and drives away, as it usually will; meanwhile your pump grinds. Running isn't the same as fine.
Not so: a two-stroke additive lets you to drive home. It is an old fix, meant for another fault. What petrol has weakened stays weakened, and that petrol remains inside that tank regardless.
Once your engine has been run, part of the petrol is in the filter and the fuel lines, not the tank — and the next start sends it straight back through your pump. So the myth "drain your tank yourself and you are sorted" doesn't stand up. Also, a can of petrol drained at the kerbside is genuinely risky.
How petrol ends up: petrol in a diesel
No one does it on purpose, and it is rarely carelessness. One way only, since of the nozzles: the narrower petrol one slides inside a diesel filler with almost no resistance, while the diesel one generally won't fit a petrol motor. That's how the forecourt makes it simple.
The moment habit stops matching your car is the moment it takes place. Hire cars, courtesy cars, and cars that are new to you. One petrol and one diesel on the drive of the same household. A forecourt you know, but with its pumps laid out differently. Filling up in a rush on the way to Hilsea, with a train to catch. The first fill-up in a diesel Volkswagen Golf after years of driving petrol is exactly the moment it takes place. The hand does what it has always done when you add rain, a phone call or a back seat full of children.
Preventing petrol in a diesel next time you fill up around Vicarage Row
- Green for unleaded and black for diesel is usual in the UK — but not on every forecourt. Go by the label on the pump, not the colour.
- Plenty of vehicles state the fuel type inside the filler flap or on the cap, and so check there on the first fill in any car you don't know.
- Label your key. In a household with one of each, a coloured fob or a sticker on your diesel's key does more than any amount of meaning to remember.
- It sounds daft and it works: on your first fill in a new or hired car, say "diesel" aloud before you take the nozzle off the pump.
- Put your phone away. This is an easy mistake to make whilst you are thinking about something else.
- A misfuel inhibitor helps, up to a point. Some diesels come with a filler designed to block a petrol nozzle, and add-on devices are available for cars without one. They are a safety net, not a reason to stop reading the pump.
- Less petrol makes a thinner blend, so stop as soon as you realise — while remembering that your next step is unchanged. It's still not to start it.
Put petrol in a diesel in Vicarage Row already?
The order of things is brief, then. Starting it is out, and so is turning on your ignition. Ask the staff to help you push it away from the pump if you're still on the forecourt, whether that is Shell or anywhere else. Next, 0333 366 0103. We will ask what was put in, about how much, and if it's been run.
If it was AdBlue instead of petrol, say so. That's a different issue — corrosion and deposits and not lost lubrication — and it has its own page for Vicarage Row.
Vicarage Row petrol in a diesel tasks: why one costs more than another
Four different tasks sit behind the four scenarios above — which is why there's no honest single quote. The scenario itself does most of the work of moving your cost. Where your car is matters too, and whether a technician can safely get to it, after the share of petrol to what that tank holds.
That's why we ask three questions before pricing instead of after: what went in, how much, and if it's run. A range turns into a straight figure when those replies are in.
About Vicarage Row, briefly
Vicarage Row is a coastal locality in Hampshire, situated near the city of Portsmouth and close to the neighbouring areas of St Francis Court and Hilsea. Vicarage Row lies at a low elevation of around 2 metres, reflecting its proximity to the sea. Vicarage Row is characterized by predominantly flat-type housing, which is common in many coastal areas of southern England.
Fuel drain cover across Hampshire, Vicarage Row included
St Francis Court, Hilsea and Highbury are among the locations around Vicarage Row that the same teams work, answering petrol in diesel call-outs across Vicarage Row's PO postcode area. Our technicians drain where the vehicle is — your own drive, a lay-by, a supermarket car park, a forecourt — so it never needs to come to us.
Still at the pump in Vicarage Row?
The best position there is, then — that is where you are. Keep it off. Phone.