Petrol in a Diesel Car in Milehouse: How Worried Should You Be?
Likely less than you already are — provided no one has started the car. Petrol resting in a diesel tank does nothing to your engine till something pulls it through the fuel system — the ignition priming the pump, the starter, or the drive on its own. So the truthful answer to the first query everyone around Milehouse asks, "have I ruined it?", is normally no. Petrol in Diesel is who to ring, with the motor left off, so it stays that way. Below, this page sets out what petrol actually does inside a diesel, how far it might have gone, and how to stop it happening to you a second time.
Inside the motor: what petrol in a diesel really does
On its way through a motor, diesel does two tasks. It ignites, and before it ignites it protects. The high-pressure pump and the injectors are made to very fine gaps, and the diesel passing through them is what keeps those surfaces from wearing against one another.
The second task petrol does not do at all, and the first it does badly. Being less viscous than diesel, petrol strips out the lubrication a fuel system needs, so a pump on the mixture wearing itself. It's also made to resist igniting under compression — the opposite of what a diesel needs — which is why you get the rattling.
Put these together and the shape of the trouble is plain. Contact does not do the damage — circulation does. Petrol in the tank is a fuel fault. A pump that has been working on that petrol is the start of a mechanical one, and whatever a worn pump sheds travels on with the fuel to the fuel injectors further on.
How bad is petrol in a diesel? Four situations our technicians see around Milehouse
The best case there can be: filled up, not once started. Being at a forecourt is what makes this the case: elsewhere, the car has been driven there to begin with. With that petrol held in that tank alone, it's cleared and flushed on the spot, and nothing more is needed.
Ignition on, or started for a second. Petrol has left that tank and reached your filter and the lines, because the system has been bled. That's usually still a simple job — a drain, a flush, and your filter seen to.
Those few miles on the road meant your pump labouring on fuel diluted by petrol the whole way. Tank, lines, filter, then clean fuel put through the whole system: that's the work, and the way your car was driven counts as much as the distance. Short trips, such as the school run to Ford Primary School, are one thing. Getting as far as Plymouth, under 3 miles away, makes a very different task — as does any miles on the M5, under 50 miles from Milehouse, with the motor working hard all the way.
Rattling, an uneven idle, smoke, a throttle gone soft: driven until it complained. What you are hearing is the motor signalling fuel that no longer acts like diesel. Whether it is the verge on Bartholomew Road, a lay-by or a side road, stop where you are and leave it. Permanent damage is very rare when a vehicle is pulled over quickly, and the fuel drain and flush that still go first take care of it.
What Milehouse 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 will be fine." It will not. A fuller tank of the same mix is all you get, because topping up takes out nothing. A diesel fuel system doesn't tolerate petrol by percentage in the way that guidance supposes.
"Current diesels can handle a little petrol" — a myth, and closer to the opposite. Lubrication matters more on newer diesels, not less, since their fuel runs through smaller components at higher pressure.
"It starts, it drives, and so no harm done" — the myth that trips up more motorists than any other. Feed diesel to a petrol engine and it normally won't run, so the motorist stops — and the damage stops with them. A diesel fed petrol usually starts, idles and drives away as though nothing has happened, whilst your pump grinds. Fine and running are not the same at all.
An old workaround for a different problem is behind this one. Myth: "Add some two-stroke oil and drive the vehicle home." That petrol is still in your tank afterwards, and what it has thinned is not put back.
Myth: "Drain your tank yourself and you are sorted." Once your engine has been run, some of the petrol is no longer in your tank: it is in the fuel filter and the lines, and it goes straight back through your pump on your next start. Draining petrol into a can at the kerbside is also really hazardous.
Petrol in a diesel: how does it occur?
It is seldom carelessness, and no one does it on purpose. A diesel nozzle generally will not fit a petrol car, yet the smaller petrol nozzle goes into the filler of a diesel almost without resistance — so forecourts make this one mistake simple, and just in that direction.
The moment routine stops matching your car is the moment it happens. A new motor, a hire car or a courtesy car. Two cars on one driveway, one petrol, one diesel. Your normal forecourt, its pumps now in a different order. Filling up in a hurry on the way to Devonport, with a train to catch. The first fill-up in a diesel BMW 3 Series after years of driving petrol is precisely the moment it takes place. Add a back seat full of children, a phone call or rain, and habit wins.
Next time you fill up in Milehouse: preventing petrol in a diesel
- The label is what counts, and so check the pump rather than the colour: in the UK unleaded handles are normally green and diesel black, but not on each forecourt.
- The first fill in an unfamiliar motor is the time to check your filler flap — on it, or on the cap, many cars state which fuel they take.
- One of each in the house? Label the key to the diesel — a bright fob, a sticker — because meaning to remember isn't enough.
- Before the nozzle comes off the petrol pump the first time you fill a hired or new vehicle, say "diesel" out loud. Silly, yes, yet it does the trick.
- Tuck your phone away. This is an easy mistake to make whilst you are thinking about something else.
- A misfuel inhibitor helps, up to a point. Some diesels have a filler designed to block a petrol nozzle, and add-on devices exist for vehicles without one. They are a backstop, not a reason to stop reading the petrol pump.
- Noticing it mid-fill? Stop at once. A thinner blend results from less petrol in the tank, yet your next step stays the same: don't crank it.
Milehouse: already put petrol in a diesel?
Then, there's only a short order of things. Never fire it up, and don't switch your ignition on. If you're still at the forecourt — Esso or anywhere else — ask the attendants to help you roll it away from the petrol pump. Then call 0333 366 0103 and tell us what was put in, roughly how much, and if it has run.
Corrosion and deposits are the problem with AdBlue, where petrol brings lost lubrication. So if it was AdBlue, say so — and see its own Milehouse page.
Milehouse petrol in a diesel tasks: why one costs more than another
The four scenarios above are four different jobs, so no single quote for this would be honest. The scenario itself does most of the work of moving the cost. Where the vehicle is counts too, and whether our van can safely get to it, after the ratio of petrol to what that tank takes.
That is why our engineers ask three questions before quoting instead of after: what was put in, how much, and if it has run. Given those answers, there is a straight figure rather than a range.
About Milehouse and where it is
Milehouse is a suburban area located on the coast of Devon, near the city of Plymouth. Milehouse sits at an elevation of 37 metres, close to the waterfront and adjacent to nearby neighbourhoods such as Ford and North Prospect. Milehouse is characterized by its predominantly terraced housing stock, reflecting the area's history of dense residential development. Milehouse is situated approximately 1.3 miles from Plymouth city centre, making it a convenient and popular place to live.
Fuel drain cover around Milehouse and across Devon
Petrol in diesel jobs around Milehouse — part of the PL postcode area — go to vans that also cover the places around it, Ford, North Prospect and Stoke among them. You need not move your car to us. Forecourts, supermarket car parks, lay-bys and your own driveway are all locations where we work.
Milehouse: still at the petrol pump?
The best place there is, then — that's where you are. Turned off it stays; then call.