Petrol in a Diesel Car in Plaistow: How Worried Should You Be?
Less than you likely are, provided it has not been started. Petrol resting in a diesel tank does nothing to your engine until something draws it through the system — the ignition priming your pump, your starter, or the drive itself. So the fair answer to the first question everyone around Plaistow asks, "have I ruined it?", is usually no. To leave the vehicle like that, phone Petrol in Diesel then leave your motor alone. The rest of this page covers what petrol actually does to a diesel, how to judge how far it has got, and how to make sure it does not happen to you again.
Inside your engine: what petrol in a diesel really does
Passing through an engine, diesel is doing two things at once. Lubricating comes before burning; it does both. What keeps 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 made to very fine clearances.
Of those two tasks, petrol manages the first poorly and the second not at all. It's thinner than diesel and takes away the lubrication the system depends on, so a pump running on a petrol mix is a pump wearing itself. And petrol is designed to resist igniting under compression, which is the opposite of what a diesel needs from its fuel. That's where the knocking comes from.
Put those together and the shape of the problem is plain. The damage is done by movement, not by contact. Petrol in the tank is a fuel issue. After the pump has been working on that petrol, a mechanical fault has started: anything shed by a pump that's wearing down is carried downstream to the injectors with the fuel.
Four scenarios our technicians see around Plaistow: how bad is petrol in a diesel?
Fuelled, and not started: no case is better. Being on a forecourt is what makes this the case: elsewhere, the car has been driven there to begin with. With the petrol kept inside the tank alone, it is cleared and cleaned on the spot, and nothing more is needed.
Ignition on, or started for a second. Once primed, the system has pulled petrol from your tank as far as the filter and the lines. Still normally easy: drain, flush, and the filter sorted.
The pump has worked a few miles on thinned fuel — that's what driving the vehicle meant. The work is the tank, the fuel lines, your filter and clean fuel through the whole system, and how hard the vehicle was driven counts as much as how far. Short trips, such as the school run to Burnt Ash Primary School, are one thing. Getting as far as London, under 10 miles away, makes a very different task — as does any mileage on the M25, under 10 miles from Plaistow, with the engine working hard all the way.
Driven on till it protested — knocking, smoke, a lumpy idle, a dead throttle. What you are hearing is the engine signalling fuel that no longer runs like diesel. Whether it's the verge on Sudbury Crescent, a lay-by or a side street, stop where you are and leave it. Long-term damage is very unusual when a vehicle is pulled over soon, and the fuel drain and flush that still go first sort it out.
What Plaistow motorists get told about petrol in a diesel — and the stories in it
Myth: topping up to full with diesel makes it fine. It doesn't. Topping up removes nothing; it gives you a bigger tank of the same mix. That advice supposes a diesel fuel system handles petrol by percentage. It does not.
Myth: "A current diesel can cope with a bit of petrol." If anything, the reverse. At higher pressure, through finer components: that is how a modern diesel moves its fuel, so the lubrication matters more, not less.
"It starts, it drives, and so no harm done" — the myth that trips up more people than any other. Any petrol motor fed diesel generally will not run, so the motorist stops and the damage stops with them. Feed petrol to a diesel and it usually fires up, ticks over and drives away like nothing happened — all while its pump wears. Being able to run isn't proof of being fine.
Myth: "Add some two-stroke oil and drive it home." It's an outdated fix for a separate issue. It does not put back what petrol has weakened, and the petrol is still in your tank after that.
If your engine has run, part of the petrol sits in your filter and your lines, not the tank — and your next start pulls it straight back through your pump. So the myth "drain that tank yourself and you're sorted" doesn't stand up. Draining petrol into a can by the roadside is also really dangerous.
How it happens: petrol in a diesel
On purpose? Never. Through carelessness? Rarely, if ever. The petrol nozzle is the slimmer of the two and slides into a diesel filler with almost no resistance; a diesel nozzle mostly won't go into a petrol motor at all. The forecourt makes it easy, and the error runs one way.
It happens when habit and the vehicle stop matching. Hire cars, courtesy cars, and cars that are new to you. A household with one petrol and one diesel on the drive. Your ordinary forecourt, its pumps suddenly in a different order. A train to catch, and a rushed fill on the way to Sundridge Park. A new-to-you diesel Renault Megane, its first fuelling, and a motorist accustomed to petrol: precisely when it occurs. With rain, a call coming in, or children to deal with, the hand just does what it always has.
Next time you fill up around Plaistow: avoiding petrol in a diesel
- The label is what counts, and so read the petrol pump instead of the colour: in the UK unleaded handles are normally green and diesel black, but not on every forecourt.
- The first fill in a new motor is the time to check the filler flap — on it, or on the cap, plenty of cars state the fuel to use.
- Good intentions do less than a sticker or a fob in a bright colour on your diesel's key when a house has one of each. So label it.
- Before the nozzle leaves the pump the first time you fill a hired or new vehicle, say "diesel" aloud. Silly, yes, but it does the trick.
- Tuck your phone away. This is an easy mistake to make while you're thinking about something else.
- Some diesels come with a filler designed to reject a petrol nozzle, and devices you can add are available for vehicles without one. Such an inhibitor helps up to a point — as a backstop, not a reason to stop checking the petrol pump.
- Noticing it halfway? Stop there and then. A thinner blend follows from less petrol inside the tank, but the next step stays the same: do not start it.
Put petrol in a diesel around Plaistow already?
The order of things is brief, then. Do not start the vehicle, and do not switch your ignition on. The attendants at the forecourt — whether at Shell itself or wherever you filled up — will usually help push it away from the pump if you ask. What was put in, about how much, and whether it has run: tell us those when you call 0333 366 0103.
Corrosion and deposits are the issue with AdBlue, whereas petrol means lost lubrication. So if it was AdBlue, say so — and read its own Plaistow page.
Plaistow petrol in a diesel tasks: why one costs more than another
Four separate jobs lie behind the four scenarios above — which is why there's no honest single price. The scenario itself does most of the work of moving your cost. Where your car is counts too, and whether a technician can safely get to it, after the ratio of petrol to what that tank takes.
What got in, how much, and if it has run — three queries our technicians ask before quoting, not after, for precisely that reason. A range becomes a straight figure when those answers are in.
About Plaistow itself
Plaistow is a suburban area in south-east London, situated near the River Thames and close to the cities of London and Greenwich. Plaistow sits at an elevation of around 53 metres, with its riverside location influencing its development and character. Plaistow is surrounded by other suburban areas, including Downham, Sundridge, and Grove Park, and is home to a population of approximately 8934 people, predominantly living in terraced housing.
Fuel drain cover in Plaistow and across Greater London
Petrol in diesel call-outs around Plaistow — part of the BR postcode area — go to vans that also cover the places round it, Downham, Sundridge and Grove Park included. The vehicle does not need to move to us: our engineers drain at a forecourt, in a supermarket car park, in a lay-by or on your own drive.
Plaistow: still at the pump?
In that case, you could not be in a better position. Turned off it remains; then call.