Petrol in a Diesel Car in Blackheath: How Worried Should You Be?
If it has not been started, you can worry less than you likely are. Petrol sitting in a diesel tank does nothing to your engine until something pulls it through the system — the ignition priming your pump, the starter, or the drive itself. So the honest answer to the first question anyone around Blackheath asks, "have I ruined it?", is generally no. To keep the vehicle like that, ring Petrol in Diesel then leave your engine switched off. The rest of this page explains what petrol really does to a diesel, how to judge how far it has got, and how to make sure it doesn't happen to you again.
What petrol in a diesel does to the motor
On its way through an engine, diesel does two tasks. Before it ignites, it lubricates — then it combusts. Very fine clearances go into the injectors and your high-pressure pump, and only your diesel running through keeps those surfaces from grinding together.
The second job petrol does not do at all, and the first it does badly. A pump working on a petrol mix is wearing itself out, because petrol is thinner than diesel and takes away the lubrication the fuel system relies on. Petrol is also made to resist igniting under compression — the opposite of what a diesel needs from its fuel — and that's where any clattering starts.
The shape of the trouble is clear when you put those together. Not contact but movement is what causes the harm. All a tank with petrol in it amounts to is a fuel problem. A pump that has been working on that petrol is the start of a mechanical one, and whatever a worn pump sheds moves on with your fuel to the injectors further on.
How bad is petrol in a diesel? Four scenarios we see around Blackheath
Filled but never started — as good as it gets. On a forecourt, and genuinely only there, the petrol is still limited to the tank — because anywhere else the car was driven to get to it. The job is draining and cleaning on the spot.
Ignition on, or started for a moment. The fuel system has been bled, and so petrol has left the tank and got to the filter and the fuel lines. Still normally simple: drain, flush, and your filter dealt with.
The pump has worked a couple of miles on weakened fuel — that's what driving it meant. Tank, lines, filter, then clean fuel put through the whole circuit: that's this work, and the way the car was driven matters as much as the miles. On the school run to All Saints' Church of England Primary School Blackheath, the distance is small. Very different once more: a run to London, under 10 miles away, or some miles on the M11, under 10 miles from Blackheath, where the engine kept labouring hard.
It protested, and only then stopped: smoke, rattling, a throttle gone soft, an idle gone ragged. The engine is telling you the fuel is no longer acting like diesel. Stop wherever you are — the verge on Orchard Road, a lay-by, a side street — then leave the car there. What goes first is still the drain and flush, and that takes care of it, with lasting damage very unusual if a car is stopped soon.
Stories Blackheath drivers hear about petrol in a diesel
Myth: "Fill it the rest of the way with diesel and it will be fine." It will not. Topping up takes out nothing; it gives you a bigger tank of the same mix. The assumption behind that guidance — that diesel fuel systems tolerate petrol by percentage — is wrong.
If anything, the opposite holds. Myth: "A newer diesel can cope with a bit of petrol." Protection matters more on newer diesels, not less, because their fuel runs through more precise parts at higher pressure.
The myth that catches drivers out: if it starts and drives, it must be unharmed. Diesel in a petrol motor normally leaves a motor that won't run: the motorist stops, and so does the damage. Whilst your pump wears, a diesel fed petrol usually starts, idles and drives away as if nothing has happened. Being able to run is not proof of being fine.
An outdated fix for a distinct issue is behind this one. Myth: "Add some two-stroke oil and drive it home." It doesn't put back what petrol has diluted, and the petrol is still in your tank later.
If the engine has been run, part of the petrol is in the fuel filter and the lines, not your tank — and your next start sends it right back through your pump. So the myth "drain your tank yourself and you are sorted" does not hold. And, a can of petrol drained by the roadside is truly dangerous.
How does petrol in a diesel occur?
It is seldom carelessness, and nobody does it on purpose. A diesel nozzle mostly won't go into a petrol car, yet the narrower petrol nozzle goes into the filler of a diesel nearly without resistance — so forecourts make this one mistake simple, and only in that direction.
Routine and the vehicle getting out of step is how it occurs. A new car, a hire car or a courtesy car. Two motors on one drive, one petrol, one diesel. The pumps in a different order on a familiar forecourt. Fuelling up in a rush on the way to the nearest station, with a train to catch. Exactly the moment it occurs: after years of driving petrol, someone fills a diesel Volkswagen Golf for the first time. With rain, a call coming in, or children to deal with, your hand simply does what it has always done.
Blackheath people: how to prevent petrol in a diesel next time
- The label is what counts, so read the pump instead of the colour: in the UK unleaded handles are usually green and diesel black, but not on each forecourt.
- Inspect your filler flap. Many cars state the fuel inside the flap or on the cap. Look at it on your first fill in a motor you do not know.
- Good intentions count for less than a sticker or a fob in a vivid colour on your diesel's key when a household has one of each. So label it.
- It sounds silly and it does the trick: on the first fill in a new or hired car, say "diesel" aloud before you take the nozzle off the petrol pump.
- Thinking about something else is when this becomes an easy mistake to make, and so put your phone away then keep your mind on the pump.
- Add-on devices are available for motors without one, and some diesels come with a filler that won't take a petrol nozzle. Helpful — but a safety net at best, never a reason to stop checking the label.
- Noticing it halfway? Stop there and then. A weaker mix results from less petrol in that tank, yet the next stage remains the same: don't crank it.
Put petrol in a diesel around Blackheath already?
Then the order of things is brief. Leave it unstarted, with your ignition off as well. If you are still on the forecourt — Tesco or anywhere else — ask the staff to help you push the car away from the pump. Next, 0333 366 0103. We will ask what went in, roughly how much, and if it has been run.
Say so if it was AdBlue rather than petrol: it is a separate fault, with its own page for Blackheath, since AdBlue brings corrosion and deposits instead of lost protection.
Why one petrol in a diesel job in Blackheath costs more than another
Four separate tasks lie behind the four situations above — which is why there's no fair single price. What shifts your cost is mostly which of them you are in. Next it is the share — how much petrol went in against how much your tank holds — and after that where the vehicle is and whether our van can reach it safely.
What was put in, how much, and if it's run — three questions our technicians ask before pricing, not after, for exactly that reason. The answers turn a range into a straight figure.
About Blackheath, for a moment
Blackheath is a suburban area in southeast London, situated on a plateau at an elevation of 39 metres above sea level. Blackheath is characterised by its predominantly flat housing stock, with many residents living in apartments. Blackheath is located near several notable areas, including Blackheath Royal Standard, Blackheath Park, and the historic borough of Greenwich. Blackheath is home to a population of approximately 4855 people, who enjoy its proximity to central London, just 6.1 miles away.
Fuel drain cover across Greater London, Blackheath included
Blackheath waits in the SE postcode area, and our vans that answer petrol in diesel calls there work the locations around it as well — Blackheath Royal Standard, Blackheath Park and Greenwich among them. No need to move the vehicle to us. Forecourts, supermarket car parks, lay-bys and your own driveway are all places we drain.
In Blackheath and still at the petrol pump?
The best place there is, then — that is where you are. Leave the car switched off, and ring.