Should You Worry? Petrol in a Diesel Car in Frognal
Not started? Then less worried than you probably feel. Petrol resting in a diesel tank does nothing to your motor till something pulls it through your fuel system — your ignition priming your pump, the starter, or the drive on its own. So the truthful answer to the first question anyone in Frognal asks, "have I ruined it?", is usually no. Leave the engine off and ring Petrol in Diesel — that keeps it that way. Read on for three things: the effect petrol has inside a diesel motor, the clues of how far it has got, and ways to make sure you don't do it again.
Petrol in a diesel: what does it do to your engine?
Two tasks fall to diesel on its route through a motor. It burns, and before it ignites it protects. Your high-pressure pump and the fuel injectors are built to very fine gaps, and the diesel passing through them is what stops those surfaces from wearing down 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 wearing itself. It's also made to resist igniting under compression — the opposite of what a diesel needs — which is where you hear the knocking.
Combined, those leave the shape of the trouble clear. Contact doesn't do the harm — movement does. Where that petrol is only in the tank, it is a fault of fuel, nothing more. A pump that has been running on that petrol is the start of a mechanical one, and whatever a worn pump sheds moves on with the fuel to the injectors downstream.
How bad is petrol in a diesel? Four situations our engineers see around Frognal
Filled up, not once started. The best case there is. Only that tank has petrol in it, so the job is emptying the tank and cleaning the fuel system where the vehicle sits. This scenario can only truly take place at a forecourt: anywhere else, the vehicle got there by being driven.
Started for a moment, or only the ignition on. Your system has been bled, and so petrol has left that tank and reached your filter and the fuel lines. Drain, flush, deal with your filter: still normally straightforward.
Those few miles driven were your pump labouring on fuel weakened by petrol the whole way. The work is your tank, your lines, the filter and clean fuel through the entire system, and how hard the car was driven counts as much as how far. On the school run to Hampstead Parochial Church of England Primary School, the distance is short. Very different once more: a run to Westminster, under 5 miles away, or any miles on the M1, under 3 miles from Frognal, where the motor kept labouring hard.
Knocking, 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. Whether it is the verge on Frognal Close, a lay-by or a side street, stop there then leave it. What comes first is still the drain and flush-through, and that deals with it, with lasting damage very rare if a car is stopped early.
Frognal drivers and the petrol in a diesel myths they hear
Myth: "Fill it the rest of the way with diesel and it'll be fine." It will not. Topping up removes nothing; it gives you a fuller tank of the same mix. Percentage is not how a diesel fuel system copes with petrol, whatever that guidance supposes.
Myth: "A modern diesel can cope with a bit of petrol." If anything, the reverse. Lubrication counts more on newer diesels, not less, because their fuel passes through more precise components at higher pressure.
"It starts, it drives, and so there is no harm" — the myth that trips up more people than any other. Feed diesel to a petrol engine and it generally will not run, and so the motorist stops — and the harm stops with them. Whilst your pump grinds, a diesel fed petrol usually starts, ticks over and drives away as if nothing has happened. Running isn't the same as fine.
"A drop of two-stroke oil and drive it home" — a myth, taken from a fix from years ago, for a different problem. It does not put back what petrol has weakened, and that petrol is still in the tank later on.
The next start sends petrol back round the pump out of the lines and your filter, where some of it ends up once the motor has been run. That is why a DIY tank drain does not sort it — a myth. Clearing petrol into a can by the kerbside is also genuinely risky.
How petrol ends up: petrol in a diesel
Nobody does it on purpose, and it's seldom carelessness. A diesel nozzle generally won't fit a petrol vehicle, but the smaller petrol nozzle goes into the filler of a diesel almost without resistance — so forecourts make this one error straightforward, and only in that direction.
Routine and the vehicle getting out of step is when it occurs. A new car, a hire car or a courtesy car. Two vehicles on one driveway, one petrol, one diesel. A forecourt you know, only with its pumps arranged differently. Racing for a train at Finchley Road & Frognal and fuelling up en route. The first fill-up in a diesel Renault Megane after years of driving petrol is precisely the moment it occurs. Throw in a back seat full of kids, a phone call or rain, and habit takes over.
Frognal drivers: how to prevent petrol in a diesel next time
- Check the pump, not the colour. In the UK unleaded handles are generally green and diesel black, but not on each forecourt. The label is what matters.
- Many motors state the fuel inside your filler flap or on the cap, and so check it on the first fill in a vehicle you do not know.
- One of each in the house? Mark your key to your diesel — a coloured fob, a sticker — because intending to remember isn't enough.
- Say it before you lift it. On your first fill in a new or hired car, say "diesel" aloud before you lift the nozzle off the petrol pump. It sounds daft and it does the trick.
- Mistakes like this are simple to make while your mind is on something else, so the phone goes away.
- Up to a point, a misfuel inhibitor helps: some diesels come with a filler designed to block a petrol nozzle, and aftermarket devices exist for the remainder. Treat it as a backstop, and keep reading the petrol pump.
- Less petrol makes a weaker blend, so stop the moment you notice — though remembering that your next stage is unchanged. It is still not to fire it up.
Frognal: already put petrol in a diesel?
Then the order of things is short. Don't start it, and do not switch your ignition on. Ask the attendants to help you push it clear of the petrol pump if you are still at the forecourt, whether that is BP or somewhere else. Then ring 0333 366 0103 and tell us what was put in, about how much, and whether it's run.
AdBlue, not petrol? Then say so. Corrosion and deposits, not lost lubrication, make it a different issue — Frognal has a page just for it.
Why one petrol in a diesel job around Frognal costs more than another
A fair single quote doesn't exist here: four situations, four separate tasks. Which of them you are in is mostly what shifts your cost. The proportion counts next, meaning how much of your tank is petrol, followed by the location of your car and whether getting to it is safe for a van.
That is why our engineers ask three queries before quoting rather than after: what was put in, how much, and whether it's run. Those answers change a range into a straight figure.
About Frognal itself
Frognal is a suburban area in northwest London, situated near the riverside and close to the neighbouring districts of Hampstead and West Hampstead. Frognal sits at an elevation of around 116 metres, with many of its residents living in flat dwellings. Frognal is located approximately 3.9 miles from central London and 4.3 miles from Westminster, making it a popular choice for those who work in the city. Frognal has a population of around 13390 people, according to recent estimates.
Fuel drain cover across Greater London, Frognal included
Petrol in diesel jobs around Frognal — part of the NW postcode area — go to vans that also cover the places around it, Hampstead, Vale of Health and West Hampstead included. No need to move your car to us. Forecourts, supermarket car parks, lay-bys and your own drive are all locations where we work.
In Frognal and still at the petrol pump?
In that case, you couldn't be in a better position. Keep the car switched off, then ring.