How Worried Should You Be? Petrol in a Diesel Car in Downfield
Less than you likely are, provided it has not been started. Till the ignition primes your pump, the starter turns, or the car is driven, petrol in a diesel tank just sits there and does no harm. Which makes the honest reply to the first Downfield query — "have I ruined it?" — normally no. Petrol in Diesel is who to ring, with the motor kept off, so it stays that way. 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 is the remainder of this page.
What petrol in a diesel does to your engine
On its way through a motor, diesel does two jobs. It burns, and before it ignites it protects. Your high-pressure pump and the injectors are designed to extremely fine gaps, and the diesel passing through them is what stops those surfaces from grinding against one another.
The second job petrol does not do at all, and the first it does badly. The clattering comes from petrol being designed not to ignite when compressed, which is precisely the opposite of what a diesel needs. On top of that it is runnier than diesel, it strips out the lubrication the fuel system rests on, and any pump working on such a mixture is wearing itself.
Put these together and the shape of the trouble is clear. Contact doesn't do the harm — circulation does. Petrol in the tank is a fuel fault. Whatever a worn pump sheds goes on, carried by your fuel, into the fuel injectors downstream, which is why a pump that has worked on that petrol is where a mechanical problem begins.
Four situations we see in Downfield: how bad is petrol in a diesel?
Filled up, never started. The best case there is. The petrol is in the tank and just that tank, and the job is a drain and a flush where the vehicle sits. This is the one scenario that can only really happen at a forecourt, since anywhere else your car has been driven to get there.
Your ignition turned on, or a short start. With your system primed, your lines and filter now contain petrol that came from that tank. Still normally simple: drain, flush, and your filter seen to.
Some miles driven, and the pump has spent each of them labouring on diluted fuel. Tank, lines, filter, then fresh fuel run through the entire circuit: that is the work, and the way the vehicle was driven counts as much as the distance. Short trips, like the school run to the local primary school, are one thing. Any distance on the M90, under 25 miles from Downfield, means the engine has worked hard throughout, and a run to Dundee, under 3 miles away, makes a very different job as well.
It complained, and only then stopped: smoke, knocking, a throttle gone soft, an idle gone lumpy. The fuel is not acting like diesel any more, and your motor is saying so. Pull up on the spot — on the verge on Balgowan Avenue, at the kerb, down a side road — and don't move it again. A vehicle stopped early very rarely has permanent damage, because the fuel drain and the flush-through, which still go first, deal with it.
Petrol in a diesel myths Downfield people hear
"Top it up the rest of the way with diesel and it will be fine" — a myth. It won't. Topping up takes out nothing; it gives you a bigger tank of the same mix. Percentage isn't how a diesel fuel system tolerates petrol, however much that guidance presumes.
Myth: "A modern diesel can cope with a bit of petrol." If anything, the opposite. A modern diesel sends its fuel through smaller components at higher pressure, which makes the protection count more, not less.
This is the one that fools drivers. Myth: "If it starts and drives, there's no harm done." Diesel in a petrol motor normally leaves a motor that won't run: the motorist stops, and so does the harm. Feed petrol to a diesel and it normally starts, idles and pulls away as if nothing happened — all the while its pump wears. Fine and running are not the same at all.
"A drop of two-stroke oil and drive it home" — a myth, borrowed from a fix from years ago, for a separate problem. That petrol is still in that tank after that, and whatever it has thinned isn't put back.
"Drain it yourself and you're sorted" — a myth, since after it has been running some petrol lies in the filter and lines, ready to go right back through your pump at the next start. And, a can of petrol drained by the roadside is genuinely dangerous.
How it happens: petrol in a diesel
A careless moment is rarely the cause, and no one means to do it. A diesel nozzle mostly won't go into a petrol vehicle, yet the narrower petrol nozzle goes into the filler of a diesel almost without resistance — so forecourts make this one error simple, and just in that direction.
When routine and the car stop matching, it takes place. Courtesy car, hire car, or a car that is brand new. Households running one of each, petrol and diesel. A familiar forecourt with the pumps in a different order. Fuelling up in a hurry on the way to Dundee, with a train to catch. A new-to-you diesel Volkswagen Golf, its first fuelling, and a motorist accustomed to petrol: exactly when it happens. With rain, a call coming in, or children to deal with, your hand just does what it has always done.
How to avoid petrol in a diesel at your next fill-up in Downfield
- Not every forecourt in the UK keeps to green for unleaded and black for diesel, though most usually do. Read the pump's label; the colour is only a hint.
- Inspect your filler flap. Many vehicles state the fuel inside the flap or on the cap. Look at it on the first fill in any motor you don't know.
- Good intentions do less than a sticker or a fob in a vivid colour on your diesel's key when a home has one of each. So mark it.
- "Diesel", out loud, before you lift the nozzle — each time a new or hired car gets its first tank. It sounds daft. It does the trick.
- While you're thinking about something else, this is an easy mistake to make — so tuck the phone away.
- Some diesels come with a filler built to block a petrol nozzle, and devices you can add are available for motors without one. Such an inhibitor helps up to a point — as a safety net, not a reason to stop reading the petrol pump.
- Less petrol makes a weaker mixture, so stop as soon as you notice — though remembering that the next step is unchanged. It's still not to start it.
Downfield: already put petrol in a diesel?
Then the order of things is brief. Do not switch your ignition on, and do not start it. The staff on the forecourt — whether at Asda itself or wherever you filled up — will usually help roll it away from the pump if you ask. Then phone 0333 366 0103 and tell us what got in, about how much, and whether it has run.
Say so if it was AdBlue rather than petrol: it is a separate fault, with its own page for Downfield, since AdBlue brings corrosion and deposits instead of lost lubrication.
Why one petrol in a diesel job around Downfield costs more than another
There is no fair single price for this, because the four scenarios above are four separate tasks. The scenario itself does most of the work of moving your cost. Where the vehicle is matters too, and whether a van can safely reach it, after the ratio of petrol to what the tank takes.
Three questions come first, before any quote, instead of after — what went in, how much, has it run — and this is the reason. Given the replies, you get a straight figure rather than a range.
About Downfield and where it is
Downfield is a suburban area located on the outskirts of Dundee, situated near the coast in eastern Scotland. Downfield sits at an elevation of 87 metres, with views of the surrounding landscape and the nearby city of Dundee. Downfield is characterized by its predominantly semi-detached housing stock, with nearby neighbourhoods including Baldovan, Trottick, and Brackens.
Fuel drain cover around Downfield and across Dundee City
The teams answering petrol in diesel jobs around Downfield, in the DD postcode area, also work the spots near it, Baldovan, Trottick and Brackens among them. The car doesn't need to come to us: we drain on a forecourt, in a supermarket car park, in a lay-by or on your own drive.
Downfield: still at the petrol pump?
The best position there is, then — that is where you are. Keep the car switched off, then ring.