Mountain: Petrol in a Diesel Car? How Worried to Be
Probably less than you are now — as long as nobody has started the vehicle. Everyone around Mountain starts with "have I wrecked it?", and the honest answer is usually no: petrol resting in the tank of a diesel remains harmless till priming, cranking or driving pulls it into your fuel system. Petrol in Diesel is who to call, with your engine kept off, and so it remains that way. The rest of this page covers what petrol actually does to a diesel, how to tell how far it has got, and how to make sure it does not happen to you again.
Your engine and petrol in a diesel: what happens
Two jobs fall to diesel on its route round a motor. Oiling comes before burning; it does both. Designed to very fine tolerances, your injectors and the pump depend on your diesel moving through them to stop their surfaces wearing against one another.
Poorly at the first, not at all at the second: that's petrol. Being less viscous than diesel, petrol strips away the lubrication a fuel system needs, leaving a pump on the mixture wearing itself. It is also made to resist igniting under compression — the reverse of what a diesel needs — which is why you hear the clattering.
Taken together, they make clear what shape the problem has. Not contact but movement is what causes the harm. A tank with petrol in it is a fuel fault. A pump that has been running on that petrol is the beginning of a mechanical one, and whatever a worn pump sheds travels on with the fuel to the injectors downstream.
How serious is petrol in a diesel? Four situations we see around Mountain
Filled but not once started — as good as it gets. The petrol is inside the tank and just that tank, and the task is a drain and a flush where the vehicle stands. This is the one scenario that can only really take place on a forecourt, as anywhere else the car has been driven to get there.
A brief spell of running, or merely the ignition on. Your system has been primed, and so petrol has left your tank and got to the fuel filter and the fuel lines. That is usually still an easy task — a drain, a flush, and your filter seen to.
Those few miles on the road were your pump labouring on fuel weakened by petrol the whole way. The work is your tank, your lines, your filter and fresh fuel through the whole circuit, and how hard the car was driven counts as much as how far. Driving the children to Foxhill Primary School is one sort of trip. Any distance on the M606, under 5 miles from Mountain, means the motor has worked hard throughout, and a run to Bradford, under 5 miles away, makes a very different task as well.
Driven till it complained. Knocking, a ragged idle, smoke, a throttle that has gone soft. The fuel is not acting like diesel any more, and the engine is telling you. Leave it wherever it stops: a lay-by, a side street, the verge on Mill Lane. Lasting damage is very unusual if a vehicle is pulled over quickly, and the fuel drain and flush that still come first sort it out.
Myths Mountain motorists hear about petrol in a diesel
"Top it up the rest of the way with diesel and it will be fine" — a myth. It won't. Nothing is removed by topping up — you're left with a fuller tank, still the same mix. Percentage isn't how a diesel fuel system copes with petrol, whatever that guidance assumes.
Not so: a current diesel copes with a bit of petrol. Rather, the opposite. A newer diesel runs its fuel through more precise components at higher pressure, which makes the protection count more, not less.
One myth that catches people off guard: if it starts and drives, it must be unharmed. Feed diesel to a petrol motor and it normally won't run, so the motorist stops — and the harm 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. Fine and running aren't the same thing.
Myth: "Add some two-stroke oil and drive the car home." It is an old workaround for a separate problem. It does not put back what petrol has thinned, and that petrol is still in the tank later on.
Myth: "Drain that tank yourself and you're sorted." After the motor has run, some of that petrol is no longer inside your tank: it's in your filter and your lines, and it goes straight back through the pump on the next start. Also, a can of petrol drained at the roadside is genuinely dangerous.
How does petrol in a diesel take place?
Nobody does it on purpose, and it's seldom carelessness. One way only, since of the nozzles: the slimmer petrol one slips inside a diesel filler with almost no resistance, whereas the diesel one generally will not fit a petrol car. That's how the forecourt makes it straightforward.
The moment habit stops matching the car is the moment it occurs. Hire cars, courtesy cars, and motors that are new to you. Households running one of each, petrol and diesel. The pumps in a different order on a familiar forecourt. Racing for a train at Halifax and filling up en route. A new-to-you diesel Volkswagen Golf, its first fuelling, and a driver used to petrol: precisely when it takes place. Add rain, a phone call or a back seat full of kids, and the hand does what it has always done.
How to prevent petrol in a diesel at your next fill-up around Mountain
- Check the pump, not the colour. In the UK unleaded handles are generally green and diesel black, yet not on each forecourt. The label is what counts.
- Inspect your filler flap. Many cars state the fuel type inside the flap or on the cap. Look at it on your first fill in any car you do not know.
- A coloured fob or a sticker on your diesel's key does more than any amount of meaning to remember, in a house with one of each.
- "Diesel", aloud, before you lift the nozzle — each time a new or hired car gets its first tank. It sounds daft. It works.
- Tuck the 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 built to reject a petrol nozzle, and add-on devices are available for motors without one. They are a backstop, not a reason to stop checking the pump.
- Noticing it mid-fill? Stop at once. A weaker blend follows from less petrol in that tank, but the next stage stays the same: do not start it.
Put petrol in a diesel around Mountain already?
In that case, there's only a short order of things. Never crank it, and do not switch the ignition on. The staff on the forecourt — whether at Esso itself or wherever you filled up — will usually help roll it clear of the pump if you ask. Next, 0333 366 0103. We'll ask what went in, roughly how much, and if it's been run.
AdBlue, not petrol? Then tell us. Corrosion and deposits, not lost lubrication, make it a different fault — Mountain has a page all for it.
What makes one Mountain petrol in a diesel task cost more than the next
An honest single price does not exist here: four scenarios, four separate jobs. What moves your cost is mostly which of them you're in. The ratio matters next, meaning how much of the tank is petrol, followed by the location of the car and whether reaching it is safe for a technician.
What got in, how much, and whether it has run — three questions we ask before quoting, not after, for precisely that reason. Those answers are what change a range into one firm number.
About Mountain
Mountain is a village in West Yorkshire, situated on the riverside at an elevation of 371 metres, with detached housing being the predominant type of accommodation. Mountain lies approximately 4.5 miles from Bradford and is surrounded by nearby places such as West Scholes, Hill Top, and Raggalds. Mountain has a population of around 683 residents and is located in a scenic area of Yorkshire. Mountain is also relatively distant from London, being around 172.7 miles away.
Fuel drain cover across West Yorkshire, Mountain included
West Scholes, Hill Top and Raggalds are among the locations near Mountain that the same teams work, answering petrol in diesel jobs across Mountain's BD postcode area. A forecourt, a supermarket car park, a lay-by or your own driveway are all spots our engineers drain, and your vehicle doesn't need to come to us.
In Mountain and still at the pump?
Then, you couldn't be in a better position. Keep it turned off, then ring.