How Worried Should You Be? Petrol in a Diesel Car in Morden
Probably less than you already are — provided no one has started the car. Petrol resting in a diesel tank does nothing to your motor until something draws it through the fuel system — your ignition priming your pump, the starter, or driving on its own. So the fair answer to the first question everyone around Morden asks, "have I ruined it?", is normally no. Petrol in Diesel is who to ring, with the engine kept off, so it stays that way. Below, you will find what petrol really does inside a diesel, how far it might have got, and how to stop it happening to you again.
Inside the engine: what petrol in a diesel really does
Diesel does two tasks on its way through an engine. Before it burns, it lubricates — and then it burns. Built to extremely fine tolerances, the injectors and your pump depend on your diesel flowing through them to stop their surfaces wearing against one another.
Of those two tasks, petrol manages the first badly and the second not at all. A pump running on a petrol mixture is wearing itself out, because petrol is thinner than diesel and takes away the lubrication your fuel system depends on. Petrol is also made to resist igniting under compression — the opposite of what a diesel needs from its fuel — and that's where the knocking comes.
Seen together, they make clear what shape the issue has. It is movement that does the damage, not contact. Where the petrol is only in that tank, it's a fault of fuel, nothing more. A pump that has been labouring on that petrol is the beginning of a mechanical one, and whatever a worn pump sheds moves on with your fuel to the injectors downstream.
Morden, petrol in a diesel: four situations, from mild to significant
Filled up, never started. The best case there can be. Just the tank has petrol in it, and so the job is draining your tank and cleaning your system where your car sits. This scenario can only truly take place on a forecourt: anywhere else, your car got there by being driven.
The ignition switched on, or a brief start. Once primed, the system has pulled petrol from your tank as far as the filter and the fuel lines. Usually nothing more than emptying, rinsing and seeing to your filter, so still simple.
The pump now worked a few miles on thinned fuel — that's what driving the car does. The work is that tank, your lines, the filter and clean fuel through the whole circuit, and how hard the vehicle was driven counts as much as how far. Driving the kids to Poplar Primary School is one kind of trip. Driving as far as Westminster, under 10 miles away, makes a very different task — as does any mileage on the M4, under 10 miles from Morden, with the motor running hard all the way.
Driven until it protested. Clattering, a lumpy idle, smoke, a throttle that has gone soft. The motor is telling you the fuel is no longer acting like diesel. Leave it wherever it has stopped: a lay-by, a quiet street, the verge on Aberconway Road. What comes first is still the fuel drain and flush, and that sorts it out, with permanent damage very uncommon when a vehicle is stopped soon.
Petrol in a diesel myths Morden drivers hear
It will not be fine. The myth: "Fill it the rest of the way with diesel and it'll be." A bigger tank of the same mix is all you get, because topping up removes nothing. The assumption behind that advice — that diesel fuel systems tolerate petrol by percentage — is wrong.
Myth: "A current diesel can cope with a bit of petrol." If anything, the reverse. A current diesel runs its fuel through smaller parts at higher pressure, which makes the lubrication count more, not less.
One myth that catches motorists off guard: if it starts and drives, it must be unharmed. A petrol engine fed diesel generally won't run, so the motorist stops and the damage stops with them. Nothing looks to have happened when a diesel fed petrol fires up, ticks over and drives away, which it usually does; meanwhile the pump wears. A running engine doesn't mean fine.
"A drop of two-stroke oil and drive it home" — a myth, taken from a fix from years ago, for a separate fault. What petrol has thinned remains weakened, and that petrol stays inside your tank regardless.
Once the motor has run, part of that petrol sits in your filter and your lines, not the tank — and your next start pulls it right back through the pump. So the myth "drain the tank yourself and you are sorted" does not hold. Besides, petrol emptied into a can by the road is truly hazardous.
Petrol in a diesel: how does it occur?
A careless moment is rarely the cause, and no one means to do it. A diesel nozzle mostly will not go into a petrol motor, yet the smaller petrol nozzle goes into the filler of a diesel almost without resistance — so forecourts make this one mistake straightforward, and only in that direction.
When habit and your car stop matching, it occurs. A new car, a hire car or a courtesy car. Two vehicles on one drive, one petrol, one diesel. Your normal forecourt, its pumps now in a different order. Filling up in a hurry on the way to Morden South, with a train to catch. The first fill-up in a diesel Volkswagen Golf after years of driving petrol is precisely the moment it takes place. Throw in a back seat full of children, a phone call or rain, and habit takes over.
Next time you fill up around Morden: avoiding petrol in a diesel
- The label is what matters, and so check the petrol pump instead of the colour: in the UK unleaded handles are normally green and diesel black, but not on every forecourt.
- In a motor you don't know, look inside the flap over the filler or at the cap before your first fill: many vehicles print the fuel there.
- One of each in the house? Label the key to your diesel — a bright fob, a sticker — because intending to remember is not enough.
- It seems daft and it does the trick: on your first fill in a new or hired car, say "diesel" out loud before you lift the nozzle off the petrol pump.
- Tuck your phone away. This is an easy mistake to make whilst you are thinking about something else.
- Add-on devices exist for motors without one, and some diesels come with a filler that will not take a petrol nozzle. Useful — but a safety net only, never a reason to stop checking the label.
- Spotting it halfway? Stop there and then. A weaker mixture follows from less petrol in that tank, yet your next stage stays the same: do not fire it up.
Put petrol in a diesel in Morden already?
Short and simple, then, is the order of things. Do not turn your ignition on, and do not crank it. Ask the staff to help you push it away from the petrol pump if you're still at the forecourt, whether that is Shell or somewhere else. Then phone 0333 366 0103 and tell us what went in, about how much, and if it's run.
Corrosion and deposits form the trouble with AdBlue, where petrol brings lost protection. So if it was AdBlue, say so — and see its own Morden page.
One petrol in a diesel task around Morden costs more than another. Why?
The four situations above are four different tasks, so no single quote for this would be honest. The scenario itself does most of the work of moving your cost. The ratio counts next, meaning how much of your tank is petrol, followed by the location of the vehicle and whether reaching it is safe for our van.
That's why our technicians ask three queries before quoting rather than after: what went in, how much, and if it's run. The replies change a range into a straight figure.
About Morden and its setting
Morden is a locality in south London, situated near the River Wandle and characterised by its terraced housing. Morden sits at an elevation of around 21 metres, close to the neighbouring areas of Merton Park and Merton. Morden is located approximately 7.8 miles from central London, with Westminster just 7.4 miles away. Morden has a population of around 4367 people, living in a mix of old and new developments.
Fuel drain cover across Greater London, Morden included
The vans answering petrol in diesel call-outs in Morden, in the SM postcode area, also work the locations around it, Risley Close, Merton Park and Merton among them. A forecourt, a supermarket car park, a lay-by or your own drive are all locations our engineers drain, and the car does not need to move to us.
At the pump in Morden, still?
The best position there is, then — that is where you are. Leave the vehicle turned off, then ring.