Bloomsbury: Petrol in a Diesel Car? How Worried to Be
Likely less than you are now — provided nobody has started it. "Have I wrecked it?" is the first thing everyone around Bloomsbury asks, and the truthful answer is normally no, since petrol resting in a diesel tank hurts nothing till it is dragged through your fuel system — by ignition priming, by the starter, or by driving. Petrol in Diesel is who to phone, with your engine left off, and so it stays that way. What petrol really does to a diesel, how to gauge how far it's gone, and how to stop it from happening a second time: that's the rest of this page.
Petrol in a diesel: what does it do to the engine?
On its way through an engine, diesel has two jobs. Lubricating comes before burning; it does both. What keeps the surfaces inside your high-pressure pump and your injectors from wearing against each other is the diesel flowing through them — they're designed to very fine tolerances.
The second job petrol does not do at all, and the first it does badly. The knocking comes from petrol being designed not to ignite when compressed, which is exactly the opposite of what a diesel needs. On top of that it is thinner than diesel, it strips out the protection the system hinges on, and any pump working on that mix is wearing itself.
Put these together and the shape of the problem is plain. Not contact but circulation is what causes the harm. Where the petrol is only in your tank, it's a fault of fuel, nothing more. Whatever a worn pump sheds goes on, borne by your fuel, into your injectors downstream, which is why a pump that has been working on the petrol is where a mechanical issue starts.
Petrol in a diesel in Bloomsbury: how serious is it? Four cases
Filled but not once started — as good as it gets. Being at a forecourt is what makes this the case: elsewhere, your car has been driven there to begin with. With that petrol held in your tank alone, it is drained and flushed on the spot, and nothing more is needed.
Ignition on, or started for a second. Petrol has come out of your tank and got to the fuel filter and your lines, since the fuel system has been primed. That is generally still an easy task — a drain, a flush, and your filter seen to.
The pump now spent a couple of miles on diluted fuel — that's what driving the vehicle meant. Miles is only half of that; how hard it was driven matters just as much. Either way this work runs to the tank, your lines, the filter and clean fuel through the whole system. On the school run to St Josephs Catholic Primary School, the mileage is small. Very different again: a run to Westminster, under 3 miles away, or any miles on the M1, under 10 miles from Bloomsbury, where the motor kept labouring hard.
Driven until it complained. Knocking, a ragged idle, smoke, a throttle that has gone soft. What you are hearing is the engine reporting fuel that no longer runs like diesel. Whether it's the verge on Russell Square, a lay-by or a side street, stop there then leave it. A car pulled over soon very rarely has long-term damage, as the drain and the flush-through, which still come first, deal with it.
Bloomsbury drivers and the petrol in a diesel stories they hear
False: topping up to full with diesel makes it fine. It doesn't. Nothing comes out when you top up — the tank simply carries more of the same mixture. Percentage is not how a diesel fuel system copes with petrol, whatever that advice assumes.
"Current diesels can handle a little petrol" — a myth, and closer to the opposite. Lubrication counts more on current diesels, not less, because their fuel passes through smaller parts at higher pressure.
"It starts, it drives, so no harm done" — the myth that trips up most motorists than any other. Diesel in a petrol motor generally means a motor that won't run: the driver stops, and so does the damage. A diesel fed petrol generally starts, ticks over and drives away as though nothing has happened, while your pump grinds. Being able to run isn't proof of being fine.
Not so: a two-stroke additive lets you to drive home. It was an old workaround, supposed for another issue. It does not put back what petrol has diluted, and that petrol is still inside your tank later.
"Drain it yourself and you are sorted" — a myth, since after it has been running some petrol sits in your filter and lines, ready to go right back through the pump on the next start. Emptying petrol into a can by the roadside is also truly risky.
Petrol in a diesel: how does it happen?
A careless moment is rarely the cause, and no one means to do it. A diesel nozzle generally will not fit a petrol motor, but the smaller petrol nozzle goes into the filler of a diesel nearly without resistance — so forecourts make this one mistake straightforward, and only in that direction.
It happens when habit and the car stop matching. Any car that is new to you — a hire car, on loan as a courtesy car, or just bought. A household with one petrol and one diesel on the driveway. The pumps in a different order on a familiar forecourt. A train to catch, and a hurried fill en route to Tottenham Court Road. Years of petrol vehicles behind you, a diesel Renault Megane in front of you at the forecourt for its first tank — that's when. The hand does what it has always done once you add rain, a phone call or a back seat full of kids.
Bloomsbury drivers: how to avoid petrol in a diesel next time
- Check the petrol pump, not the colour. In the UK unleaded handles are normally green and diesel black, but not on each forecourt. The label is what counts.
- In a vehicle you don't know, look inside the flap over the filler or at the cap before the first fill: plenty of motors state the fuel type there.
- Label the 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 does the trick: on the first fill in a new or hired car, say "diesel" aloud before you lift the nozzle off the pump.
- Put the phone away. This is an easy mistake to make while you're thinking about something else.
- Add-on devices exist for vehicles without one, and some diesels come with a filler that will not take a petrol nozzle. Helpful — but a backstop at best, never a reason to stop checking the label.
- Stop the moment you realise. Less petrol in that tank means a thinner mix. It doesn't change what to do next, which is still not to crank it.
Put petrol in a diesel around Bloomsbury already?
In that case, there's just a short order of things. Leave it unstarted, with the ignition switched off too. Ask the attendants to help you roll it clear of the pump if you're still at the forecourt, whether that is Texaco or somewhere else. What got in, roughly how much, and if it has run: tell us that when you phone 0333 366 0103.
If it was AdBlue rather than petrol, say so. That is a different problem — corrosion and deposits instead of lost lubrication — and it has its own page for Bloomsbury.
One petrol in a diesel task around Bloomsbury costs more than another. Why?
There's no honest single price for this, since the four situations above are four different jobs. What moves the cost is mostly which of them you're in. Where your car is counts too, and whether a van can safely reach it, after the share of petrol to what the tank takes.
What went in, how much, and whether it's run — three questions our engineers ask before costing, not after, for exactly that reason. Those answers are what turn a range into one firm number.
About Bloomsbury
Bloomsbury is a densely populated suburban area in central London, situated near the British Museum and several major universities. Bloomsbury sits at an elevation of around 34 metres, close to the heart of the city, with nearby areas including St Giles, Fitzrovia, and the Strand. Bloomsbury is characterized by its predominantly flat-based housing stock, accommodating a population of approximately 14265 residents. Bloomsbury is well-connected to the rest of London, being just 0.9 miles from the city centre and 1.4 miles from Westminster.
Fuel drain cover in Bloomsbury and across Greater London
The teams answering petrol in diesel calls around Bloomsbury, in the WC1B postcode area, equally work the spots around it, St Giles, Fitzrovia and Strand included. You need not move the vehicle to us. Forecourts, supermarket car parks, lay-bys and your own drive are all places we drain.
Still at the pump around Bloomsbury?
Then you're in the best place there can be. Turned off it remains; then ring.