Petrol in a Diesel Car in Foxhole: How Worried Should You Be?
If it has not been started, worry less than you likely are. Petrol resting in a diesel tank does nothing to the engine till something draws it through the system — the ignition priming your pump, your starter, or the drive on its own. So the honest answer to the first question everyone in Foxhole asks, "have I wrecked it?", is usually no. Petrol in Diesel is who to phone, with your engine left off, and so it remains that way. The remainder of this page explains what petrol actually 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 engine: what petrol in a diesel really does
Diesel has two jobs on its way through an engine. Lubricating comes before burning; it does both. What keeps the surfaces inside the high-pressure pump and your injectors from wearing down against one another is the diesel passing through them — they're made to extremely fine gaps.
The second job petrol doesn't do at all, and the first it does badly. A pump running on a petrol blend is wearing itself out, since petrol is thinner than diesel and takes away the protection the fuel system depends on. Petrol is also made to resist igniting under compression — the opposite of what a diesel wants from its fuel — and that's where the clattering starts.
Together, those leave the shape of the trouble clear. It's movement that causes the damage, not contact. Any tank with petrol in it is a fuel fault. Once the pump has been working on that petrol, a mechanical fault has begun: anything shed by a pump that's grinding is carried downstream to the injectors with the fuel.
How bad is petrol in a diesel? Four situations our engineers see in Foxhole
The best case there can be: filled up, never started. At a forecourt, and truly only there, that petrol is still confined to your tank — since anywhere else the vehicle was driven to reach it. The task is draining and flushing on the spot.
A moment's running, or merely the ignition on. Your system has been primed, so petrol has left that tank and got to the filter and your lines. Usually nothing more than emptying, flushing and sorting the fuel filter, so still simple.
The pump now worked a few miles on diluted fuel — that is what driving the vehicle does. How hard the vehicle was driven matters as much as how far, and this work covers that tank, the fuel lines, your filter and clean fuel through the whole circuit. A school run to Foxhole Learning Academy is one thing. A run as far as Truro, under 15 miles away, is a very different job. So is any miles on the M5, over 50 miles from Foxhole, where your engine has been labouring hard the whole time.
Driven until it protested. Rattling, a lumpy idle, smoke, a throttle that has gone soft. That is your motor telling you its fuel has stopped acting like diesel. Whether it's the verge on Chegwins Hill, a lay-by or a side road, stop there then leave it. A vehicle stopped early very seldom has permanent damage, as the drain and the flush, which still go first, take care of it.
What Foxhole motorists get told about petrol in a diesel — and the myths in it
Myth: "Fill it the rest of the way with diesel and it'll be fine." It will not. Nothing is removed by topping up — you're left with a bigger tank, still the same mixture. Percentage isn't how a diesel fuel system copes with petrol, however much that guidance supposes.
Myth: "A current diesel can cope with a bit of petrol." If anything, the reverse. A newer diesel runs its fuel through more precise components at higher pressure, which makes the protection count more, not less.
Myth: "If it starts and drives, there's no damage done." This is the one that catches drivers. Any petrol engine fed diesel normally won't run, and so the driver stops and the damage stops with them. While the pump grinds, a diesel fed petrol normally starts, idles and drives away as if nothing has happened. Fine and running are not the same thing.
Myth: "Add some two-stroke oil and drive the car home." It is an outdated workaround for a different issue. The petrol is still in the tank afterwards, and what it has thinned isn't put back.
Myth: "Drain your tank yourself and you're sorted." Once the engine has run, some of that petrol is no longer in that tank: it is in the fuel filter and your lines, and it goes straight back through the pump on your next start. Besides, petrol emptied into a can by the road is truly dangerous.
Petrol in a diesel: how does it occur?
It's seldom carelessness, and nobody does it on purpose. One way only, since of the nozzles: the smaller petrol one slides inside a diesel filler with almost no resistance, while the diesel one generally won't fit a petrol car. That is how the forecourt makes it simple.
When habit and the vehicle stop matching, it happens. Hire cars, courtesy cars, and motors that are new to you. Two cars on one driveway, one petrol, one diesel. The pumps in a different order on a familiar forecourt. Rushing for a train at St Austell and fuelling up en route. The first fill-up in a diesel BMW 3 Series after years of driving petrol is exactly the moment it happens. With rain, a call arriving, or children to deal with, your hand simply does what it always has.
How to prevent petrol in a diesel at your next fill-up around Foxhole
- The label is what counts, and so check the petrol pump rather than the colour: in the UK unleaded handles are normally green and diesel black, but not on every forecourt.
- Check the filler flap. Plenty of vehicles state the fuel type inside the flap or on the cap. Look at it on your first fill in a vehicle you don't know.
- Label your key. In a home with one of each, a coloured fob or a sticker on your diesel's key does more than any amount of intending to remember.
- Before the nozzle comes off the pump the first time you fill a hired or new car, say "diesel" out loud. Silly, yes, but it works.
- While you are thinking about something else, this is an easy mistake to make — so tuck the phone away.
- Some diesels have a filler designed to block a petrol nozzle, and devices you can add exist for motors without one. Such an inhibitor helps up to a point — as a backstop, not a reason to stop reading the petrol pump.
- As soon as you notice, stop: less petrol inside your tank means a weaker blend. What to do next does not change, though — still don't fire it up.
Put petrol in a diesel around Foxhole already?
Then the order of things is short. Leave it unstarted, with the ignition off as well. Ask the staff to help you roll it away from the petrol pump if you are still on the forecourt, whether that's the nearest petrol station or somewhere else. Phone 0333 366 0103 next, with three facts — your fuel, the approximate volume, and whether it has run.
Say so if it was AdBlue instead of petrol: it's a separate issue, with its own page for Foxhole, since AdBlue brings corrosion and deposits instead of lost lubrication.
Foxhole petrol in a diesel jobs: why one costs more than another
The four situations above are four different jobs, so no single price for this would be honest. Which of them you are in is mostly what shifts the cost. Where the car is counts too, and whether a technician can safely get to it, after the ratio of petrol to what the tank takes.
What got in, how much, and whether it's run — three questions our engineers ask before costing, not after, for exactly that reason. A range turns into a straight figure when those answers are in.
About Foxhole
Foxhole is a small village in Cornwall, situated inland at an elevation of 198 metres, approximately 10.6 miles from Truro. Foxhole has a population of around 1281 residents, with predominantly terraced housing. Foxhole is surrounded by nearby places such as Goverseth, Carpalla, and Goonabarn, and is located about 220.9 miles west of London.
Foxhole and Cornwall: where our fuel drain cover reaches
Foxhole rests in the PL postcode area, and our teams that answer petrol in diesel jobs there work the places near it as well — Goverseth, Carpalla and Goonabarn among them. A forecourt, a supermarket car park, a lay-by or your own driveway are all locations we work, and the car does not need to come to us.
In Foxhole and still at the pump?
Nothing beats it: that's where you now are. Leave the vehicle turned off, then ring.