Cowley Peachy: Petrol in a Diesel Car? How Worried to Be
Unstarted? Then less anxious than you probably feel. "Have I wrecked it?" is the first question anyone in Cowley Peachy asks, and the truthful answer is usually no, since petrol resting in a diesel tank harms nothing until it is drawn through your fuel system — by ignition priming, by the starter, or by driving. Keep it like that: leave the motor off and ring Petrol in Diesel. Below, this page sets out what petrol actually does inside a diesel, how far it may have got, and how to stop it happening to you a second time.
Inside the motor: what petrol in a diesel does
Diesel has two tasks on its way through a motor. It lubricates first, and only then does it burn. Designed to very fine tolerances, the injectors and the pump depend on your diesel flowing through them to stop their surfaces wearing against one another.
Petrol does the first task badly and the second not at all. The rattling comes from petrol being made 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 depends on, and any pump working on that blend is wearing itself.
Put those together and the shape of the trouble is plain. Not contact but circulation is what does the damage. Petrol in a tank is a fuel issue. 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 fuel injectors further on.
Four scenarios our technicians see in Cowley Peachy: how bad is petrol in a diesel?
Fuelled, and never started: nothing beats it. Being at a forecourt is what makes this possible: elsewhere, your car has been driven there to begin with. With that petrol kept inside the tank alone, it is drained and flushed right where it stands, and nothing more is needed.
Ignition on, or started for a second. Petrol has left your tank and reached the filter and the lines, because your system has been primed. That's usually still a simple task — a drain, a flush, and the filter seen to.
Driven a couple of miles. Now the pump has spent those miles running on weakened fuel. How hard the vehicle was driven counts as much as how far, and this work takes in that tank, the fuel lines, the filter and fresh fuel through the entire circuit. On the school run to Cowley St Laurence CofE Primary School, the mileage is small. Very different once more: a run to Westminster, under 25 miles away, or any miles on the M25, under a mile from Cowley Peachy, where the engine never stopped working hard.
Driven till it complained. Rattling, a lumpy idle, smoke, a throttle that has gone soft. What you are hearing is the engine reporting fuel that no longer acts like diesel. Stop on the spot — on the verge on High Road, at the kerb, down a side road — and don't move it again. What goes first is still the drain and flush-through, and that deals with it, with long-term damage very unusual if a car is pulled over soon.
What Cowley Peachy 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, since topping up removes nothing. Percentage isn't how a diesel fuel system copes with petrol, however much that advice supposes.
If anything, the opposite is true. Myth: "A current diesel can cope with a bit of petrol." Lubrication counts more on modern diesels, not less, because their fuel passes through more precise components at higher pressure.
One myth that catches motorists out: if it starts and drives, it must be unharmed. Any petrol motor fed diesel usually will not run, so the driver stops and the damage stops with them. While your pump grinds, a diesel fed petrol usually starts, idles and drives away as though nothing has happened. Running is not the same as fine.
"A drop of two-stroke oil and drive it home" — a myth, borrowed from a fix from years ago, for a distinct problem. None of what petrol thinned is put back by it — and afterwards, the tank still holds the petrol.
Once your engine has run, part of that petrol is in your filter and the lines, not that tank — and your next start sends it straight back through your pump. So the myth "drain your tank yourself and you are sorted" doesn't hold. Clearing petrol into a can at the roadside is also really dangerous.
How it happens: petrol in a diesel
On purpose? Never. Through carelessness? Seldom, if ever. A diesel nozzle mostly will not go into a petrol car, yet the narrower petrol nozzle goes into the filler of a diesel almost without resistance — so forecourts make this one mistake straightforward, and just in one direction.
When habit and your car stop matching, it happens. A new motor, a hire car or a courtesy car. A household with one petrol and one diesel on the driveway. A familiar forecourt with the pumps in a different order. A train to catch, and a hurried fill on the way to West Drayton. A new-to-you diesel Renault Megane, its first fuelling, and a driver accustomed to petrol: exactly when it occurs. With rain, a call arriving, or a car full of children to deal with, the hand just does what it has always done.
How to prevent petrol in a diesel on your next fill-up around Cowley Peachy
- Read the pump, not the colour. In the UK unleaded handles are normally green and diesel black, but not on each forecourt. The label is what counts.
- In a car you do not know, look inside the flap over your filler or at the cap before your first fill: many vehicles print the fuel there.
- One of each in the house? Mark your key to the diesel — a bright fob, a sticker — because meaning to remember is not enough.
- Before the nozzle leaves the petrol pump the first time you fill a hired or new car, say "diesel" out loud. Daft, yes, yet it does the trick.
- Put the phone away. This is an easy mistake to make whilst you're thinking about something else.
- Some diesels have a filler built to reject a petrol nozzle, and devices you can add are available for cars 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 means a weaker blend, and so stop as soon as you notice — while remembering that your next stage is unchanged. It is still not to start the vehicle.
Petrol already in a diesel around Cowley Peachy? Start here
The order of things is short, then. Leave it unstarted, with your ignition switched off as well. If you're still at the forecourt — Esso or anywhere else — ask the attendants to help you push it away from the petrol pump. Then ring 0333 366 0103 and tell us what got in, roughly how much, and if it's run.
If it was AdBlue instead of petrol, say so. That is a separate problem — corrosion and deposits rather than lost lubrication — and it has its own page for Cowley Peachy.
Cowley Peachy petrol in a diesel tasks: why one costs more than another
There is no fair single price for this, since the four situations above are four separate tasks. Which of them you are in is chiefly what shifts your cost. The proportion matters next, meaning how much of the tank is petrol, and then the position of your car and whether reaching it is safe for a van.
What went in, how much, and whether it's run — three questions we ask before quoting, not after, for precisely that reason. The answers change a range into a straight figure.
About Cowley Peachy and its setting
Cowley Peachy is a locality in Greater London, situated near lakes and waterways at an elevation of around 32 metres. Cowley Peachy lies approximately 15 miles west of central London, near the neighbouring areas of Little Britain and Cowley. Cowley Peachy is characterized by its predominantly flat-type housing, which reflects the urban development of the surrounding area. Cowley Peachy has a population of around 4560 residents, who live in close proximity to Westminster, which is about 15 miles away.
Cowley Peachy and Greater London: where our fuel drain cover runs
Cowley Peachy sits in the UB postcode area, and our teams that answer petrol in diesel call-outs there work the spots near it as well — Cowley Peachey, Little Britain and Cowley among them. The vehicle doesn't need to move to us: we drain on a forecourt, in a supermarket car park, in a lay-by or on your own driveway.
Still at the pump in Cowley Peachy?
Then you are in the best spot there can be. Switched off it stays; then call.