How Worried Should You Be? Petrol in a Diesel Car in Plas-Marl
Not started? Then less anxious than you probably feel. Until the ignition primes your pump, your starter cranks, or the car is driven, petrol in a diesel tank just waits there and does no harm. Which means the honest reply to that first Plas-Marl question — "have I ruined it?" — usually no. Keep it that way: leave the motor off and call Petrol in Diesel. What petrol actually does to a diesel, how to gauge how far it has gone, and how to stop it from happening a second time: that's the remainder of this page.
What petrol in a diesel does to the engine
On its way through a motor, diesel has two tasks. Before it burns, it protects — then it burns. The high-pressure fuel pump and the injectors are designed to very fine gaps, and your diesel passing through them is what stops those surfaces from wearing against each other.
Of these two tasks, petrol handles the first badly and the second not at all. A pump running on a petrol blend is wearing itself out, since petrol is thinner than diesel and takes away the lubrication your fuel system depends on. Petrol is also designed to resist igniting under compression — the opposite of what a diesel wants from its fuel — and that's where any rattling starts.
The shape of the problem is clear once 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. The start of a mechanical problem is a pump that has been running on that petrol — and whatever a worn pump sheds travels on with the fuel to the fuel injectors downstream.
Four scenarios our technicians see around Plas-Marl: how bad is petrol in a diesel?
Filled up, and not started: nothing beats it. 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's cleared and cleaned on the spot, and nothing more is needed.
Ignition on, or started for a second. Once primed, the fuel system has pulled petrol from the tank up to the fuel filter and your lines. Normally little more than draining, flushing and sorting your filter, so still straightforward.
Those few miles on the road meant the pump running on fuel weakened by petrol the whole way. The work is that tank, your lines, the filter and clean fuel through the entire system, and how hard the vehicle was driven matters as much as how far. Short trips, like the school run to the local primary school, are one thing. Very different a second time: a run to Swansea, under 3 miles away, or some distance on the M4, under 3 miles from Plas-Marl, where the engine kept labouring hard.
Rattling, an uneven idle, smoke, a throttle gone soft: driven till it complained. What you are hearing is your motor reporting fuel that no longer behaves like diesel. Leave it wherever it has stopped: a lay-by, a side street, the verge on Britannia Road. Permanent damage is very unusual when a vehicle is stopped soon, and the drain and flush that still go first take care of it.
Stories Plas-Marl drivers hear about petrol in a diesel
"Top it up the rest of the way with diesel and it'll be fine" — a myth. It will not. A fuller tank of the same mix is all it gives, because topping up takes out nothing. Percentage isn't how a diesel fuel system tolerates petrol, whatever that guidance assumes.
If anything, the reverse holds. Myth: "A modern diesel can cope with a bit of petrol." A current diesel runs its fuel through finer components at higher pressure, which makes the protection matter more, not less.
Myth: "If it starts and drives, there's no harm done." This is the one that catches motorists. Feed diesel to a petrol motor and it generally won't run, and so the motorist stops — and the damage stops with them. While your pump wears, a diesel fed petrol usually starts, idles and drives away as if nothing has happened. Running isn't the same as fine.
Myth: "Add some two-stroke oil and drive it home." It's an old workaround for a distinct problem. It doesn't put back what petrol has diluted, and that petrol is still inside the tank after that.
Myth: "Drain your tank yourself and you're sorted." After your engine has been run, some of the petrol is no longer in the tank: it is in the filter and the fuel lines, and it goes straight back through your pump at your next start. It is also really dangerous to drain petrol into a can by the roadside.
How does petrol in a diesel occur?
It's rarely carelessness, and nobody does it on purpose. One way only, because of the nozzles: the smaller petrol one slides inside a diesel filler with almost no resistance, while the diesel one mostly won't fit a petrol vehicle. That's how the forecourt makes it straightforward.
Routine and the car falling out of step is how it happens. Courtesy car, hire car, or a motor that is brand new. Two vehicles on one driveway, one petrol, one diesel. Your usual forecourt, its pumps now in a different order. Fuelling up in a hurry en route to Swansea, with a train to catch. The first fill-up in a diesel Renault Megane 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 wins.
Next time you fill up in Plas-Marl: preventing petrol in a diesel
- Not every forecourt in the UK keeps to green for unleaded and black for diesel, though most usually do. Read the petrol pump's label; the colour is only a clue.
- Inspect your filler flap. Many vehicles state the fuel inside the flap or on the cap. Look at it on the first fill in a motor you don't know.
- Good intentions do less than a sticker or a fob in a bright colour on your diesel's key when a home has one of each. So mark it.
- Before the nozzle comes off the pump the first time you fill a hired or new motor, say "diesel" out loud. Daft, yes, yet it does the trick.
- Put your phone away. This is an easy mistake to make while you are thinking about something else.
- Add-on devices are available for cars without one, and some diesels come with a filler that won't accept a petrol nozzle. Useful — but a safety net only, never a reason to stop checking the label.
- Stop as soon as you realise. Less petrol in your tank means a thinner blend. It does not change what to do next, which is still not to crank it.
Already put petrol in a diesel around Plas-Marl?
Short and simple, then, is the order of things. Leave it unstarted, with the ignition switched off as well. Still on the forecourt, at Texaco or anywhere else? Ask the staff to help you push the car clear of the pump. Next, 0333 366 0103. We will ask what went in, about how much, and if it has been run.
Say so if it was AdBlue instead of petrol: it is a different problem, with its own page for Plas-Marl, since AdBlue brings corrosion and deposits rather than lost protection.
One petrol in a diesel task around Plas-Marl costs more than another. Why?
There is no honest single quote for this, because the four situations above are four separate jobs. Chiefly, your cost shifts with which situation you're in. Where the vehicle is matters too, and whether a technician can safely reach it, after the ratio of petrol to what the tank takes.
Three queries come first, before any quote, instead of after — what went in, how much, has it run — and that is the reason. The replies turn a range into a straight figure.
About Plas-Marl and where it is
Plas-Marl is a suburban area located on the coast near Swansea, with a mix of terraced housing and local amenities. Plas-Marl sits at an elevation of 29 metres, close to the city centre and nearby communities such as Cnap-Llwyd and Landore. Plas-Marl is part of the wider Swansea urban area, with the city's maritime history and cultural attractions within easy reach. Plas-Marl has a population of around 2342 people, living in a predominantly residential environment.
Across Swansea and around Plas-Marl: fuel drain cover
Plas-Marl sits in the SA postcode area, and our vans that answer petrol in diesel calls there work the spots around it as well — Cnap-Llwyd, Landore and Graig Trewyddfa among them. The car doesn't need to move to us: our technicians drain on a forecourt, in a supermarket car park, in a lay-by or on your own driveway.
In Plas-Marl and still at the petrol pump?
Nothing beats it: that's where you are. Phone, and keep it turned off.