Petrol in a Diesel Car in Fallowfield: How Worried Should You Be?
Far less than you probably are, if it has not been started. Petrol resting in a diesel tank does nothing to the motor until something draws it through the system — your ignition priming your pump, your starter, or the drive itself. So the truthful answer to the first question anyone in Fallowfield asks, "have I ruined it?", is normally no. To keep the car like that, call Petrol in Diesel then leave the engine switched off. The rest of this page sets out what petrol really does to a diesel, how to tell how far it has got, and how to make sure it doesn't happen to you again.
Inside the motor: what petrol in a diesel does
Diesel does two jobs on its way through an engine. Before it ignites, it lubricates — then it ignites. What stops the surfaces inside the high-pressure fuel pump and your injectors from grinding against one another is your diesel passing through them — they are designed to extremely fine gaps.
The second job petrol does not do at all, and the first it does poorly. A pump running on a petrol mixture is wearing itself out, since petrol is thinner than diesel and takes away the lubrication the fuel system relies on. Petrol is also designed to resist igniting under compression — the opposite of what a diesel needs from its fuel — and that's where any knocking comes.
Combined, those make the shape of the problem clear. Contact doesn't do the harm — circulation does. All a tank with petrol in it amounts to is a fuel fault. Whatever a worn pump sheds goes on, borne by your fuel, into the injectors further along, which is why a pump that has been working on the petrol is where a mechanical problem starts.
How bad is petrol in a diesel? Four scenarios we see around Fallowfield
Filled but not once started — the best it gets. Being at a forecourt is what makes this the case: elsewhere, the vehicle has been driven there to begin with. With the petrol held in your tank alone, it's drained and purged on the spot, and nothing more is needed.
Ignition on, or started for a moment. The fuel system has been primed, so petrol has left the tank and reached the filter and the lines. Still normally straightforward: drain, flush, and your filter seen to.
Driven a few miles. Now the pump has spent these miles labouring on diluted fuel. Distance is only half of it; how hard it was driven counts just as much. Either way the work runs to that tank, the lines, your filter and fresh fuel through the whole circuit. Short trips, such as the school run to St Kentigern's RC Primary School, a Voluntary Academy, are one matter. A run as far as Manchester, under 3 miles away, is a very different task. So is any distance on the A57(M), under 3 miles from Fallowfield, where your engine has been working hard the whole time.
Driven on until it complained — knocking, smoke, a ragged idle, a soft throttle. The fuel is not acting like diesel any more, and your engine is telling you. Stop on the spot — on the verge on Hart Road, at the kerb, down a side road — and don't move it. A car stopped soon very rarely has long-term damage, because the drain and the flush-through, which still come first, sort it out.
Myths Fallowfield people hear about petrol in a diesel
Myth: "Fill it the rest of the way with diesel and it will be fine." It will not. Nothing comes out when you top up — the tank simply carries more of the same blend. The assumption behind that guidance — that diesel fuel systems accept petrol by percentage — is wrong.
Myth: "A current diesel can cope with a bit of petrol." If anything, the opposite. At higher pressure, through more precise components: that's how a modern diesel handles its fuel, and so the protection counts for more, not less.
Myth: "If it starts and drives, there's no damage done." This is the one that fools people. A petrol motor fed diesel normally will not run, so the driver stops and the harm stops with them. A diesel fed petrol normally starts, idles and drives away as if nothing has happened, while your pump wears. Running does not mean fine.
Myth: "Add some two-stroke oil and drive the car home." It is an outdated fix for a separate problem. None of what petrol weakened is put back by it — and later, your tank still contains the petrol.
If the motor has been run, part of that petrol sits in your filter and the fuel lines, not your tank — and the next start sends it right back through the pump. So the myth "drain your tank yourself and you are sorted" doesn't hold. It's also truly risky to drain petrol into a can by the roadside.
How petrol ends up: petrol in a diesel
A careless moment is rarely the cause, and no one means to do it. The forecourt makes it easy: the petrol nozzle is the narrower of the two, and it slips into a diesel filler with almost no resistance, while a diesel nozzle generally won't go into a petrol vehicle at all. So the error runs one way.
Routine and the car getting out of step is when it takes place. Hire cars, courtesy cars, and cars that are new to you. Households running one of each, petrol and diesel. A forecourt you know, only with its pumps arranged differently. Fuelling up in a hurry en route to Mauldeth Road, with a train to catch. The first fill-up in a diesel Volkswagen Golf after years of driving petrol is precisely the moment it happens. Add rain, a phone call or a back seat full of kids, and the hand repeats what it has always done.
Fallowfield motorists: how to prevent petrol in a diesel next time
- The label is what matters, so check the petrol pump rather than the colour: in the UK unleaded handles are usually green and diesel black, yet not on every forecourt.
- Check the filler flap. Many cars state the fuel type inside the flap or on the cap. Look at it on your first fill in a car you do not know.
- A coloured fob or a sticker on the diesel's key does more than any amount of meaning to remember, for a house with one of each.
- "Diesel", aloud, before you lift the nozzle — each time a new or hired car needs its first tank. It seems daft. It works.
- While you are thinking about something else, this is an easy mistake to make — so tuck your phone away.
- A misfuel inhibitor helps, up to a point. Some diesels have a filler built to reject a petrol nozzle, and add-on devices are available for vehicles without one. They are a safety net, not a reason to stop reading the pump.
- Spotting it halfway? Stop there and then. A weaker mixture results from less petrol in that tank, but your next stage stays the same: do not crank it.
Already put petrol in a diesel around Fallowfield?
In that case, there is just a short order of things. Leave it unstarted, with your ignition switched off too. Still at the forecourt, at BP or anywhere else? Ask the staff to help you roll it away from the petrol pump. Next, 0333 366 0103. We will ask what went in, about how much, and if it's been run.
AdBlue, not petrol? Then say so. Corrosion and deposits, not lost lubrication, make it a different issue — Fallowfield has a page all for it.
What makes one Fallowfield petrol in a diesel task cost more than the next
An honest single price does not exist here: four situations, four separate jobs. The scenario itself does most of the work of moving your cost. Two things follow that: the petrol that got in as a proportion of what the tank holds, then the spot the vehicle is in and whether a van can reach it safely.
That is why our technicians ask three questions before costing rather than after: what went in, how much, and if it has run. Given the replies, there is a straight figure rather than a range.
About Fallowfield
Fallowfield is a suburban area in Greater Manchester, situated near the River Mersey at an elevation of 39 metres. Fallowfield lies approximately 2.6 miles south of Manchester city centre, within a short distance of nearby places such as Withington and Rusholme. Fallowfield has a population of around 12,213 people and is characterised by semi-detached housing. Fallowfield is also close to the Infirmary and other local amenities.
Fallowfield and Greater Manchester: where our fuel drain cover runs
Petrol in diesel call-outs around Fallowfield — part of the M postcode area — go to vans that likewise cover the locations about it, Withington, Rusholme and Infirmary among them. The vehicle doesn't need to move to us: we drain on a forecourt, in a supermarket car park, in a lay-by or on your own driveway.
Still at the pump in Fallowfield?
In that case, you could not be in a better position. Keep the vehicle switched off, and ring.