Treneere: Petrol in a Diesel Car? How Worried to Be
Less than you probably are, if it hasn't been started. "Have I ruined it?" is the first thing everyone in Treneere asks, and the honest answer is usually no, since petrol left in a diesel tank harms nothing until it is drawn through the fuel system — by ignition priming, by your starter, or by driving. Leave the engine off and call Petrol in Diesel — that is how you keep it that way. The remainder of this page sets out what petrol really does to a diesel, how to tell how far it has got, and how to make sure it does not happen to you again.
Inside the motor: what petrol in a diesel really does
On its way through an engine, diesel does two tasks. Oiling comes before burning; it does both. What keeps the surfaces inside the high-pressure pump and your injectors from grinding against each other is the diesel flowing through them — they are made to extremely fine gaps.
Poorly at the first, not at all at the second: that is petrol. The rattling comes from petrol being made not to ignite when compressed, which is precisely the reverse of what a diesel needs. On top of that it is thinner than diesel, it strips away the protection the system depends on, and any pump working on that mix is wearing itself.
The shape of the problem is plain once you put those together. Not contact but movement is what causes the harm. Any tank with petrol in it is a fuel problem. 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 your injectors further on.
Treneere, petrol in a diesel: four cases, from mild to serious
Filled up, never started. The best case there is. Being on a forecourt is what makes this the case: elsewhere, the vehicle has been driven there to begin with. With the petrol held in your tank alone, it is drained and cleaned right where it stands, and nothing more is needed.
Ignition on, or started for a moment. Once primed, the fuel system has drawn petrol from the tank as far as your filter and your lines. Drain, flush, deal with the fuel filter: still normally straightforward.
Those few miles driven were your pump labouring on fuel weakened by petrol throughout. The work is your tank, the fuel lines, your filter and fresh fuel through the entire circuit, and how hard the car was driven counts as much as how far. On the school run to St Mary's Catholic School, Penzance, the mileage is short. Getting as far as Truro, under 25 miles away, makes a very different job — as does any mileage on the M5, over 50 miles from Treneere, with the motor working hard the whole time.
Driven till it protested. Rattling, a ragged idle, smoke, a throttle that has gone soft. That's the engine telling you its fuel has stopped behaving like diesel. Whether it's the verge on Polmeere Road, a lay-by or a side street, stop where you are then leave it. What goes first is still the fuel drain and flush-through, and that sorts it out, with lasting damage very rare when a car is stopped soon.
Myths Treneere motorists hear about petrol in a diesel
It will not be fine. The myth: "Fill it the rest of the way with diesel and it'll be." A fuller tank of the same mixture is all it gives, since topping up removes nothing. Percentage isn't how a diesel fuel system tolerates petrol, whatever that advice presumes.
"Modern diesels can handle a little petrol" — a myth, and closer to the opposite. Smaller components and higher pressure are how a current diesel runs its fuel, and that makes the lubrication count more, not less.
The myth that catches drivers out: if it starts and drives, it must be unharmed. A petrol motor fed diesel normally won't run, and so the motorist stops and the damage stops with them. Feed petrol to a diesel and it generally fires up, ticks over and pulls away as if nothing happened — all the while its pump wears. Being able to run isn't the same as being fine.
Myth: a two-stroke additive lets you to drive home. It is an old fix, meant for another problem. That petrol is still in the tank after that, and what it has thinned is not put back.
The next start draws petrol back round your pump from the fuel lines and your filter, where some of that ends up once the motor has run. That is why draining the tank yourself does not sort it — a myth. It's also really hazardous to drain petrol into a can by the kerbside.
How it happens: petrol in a diesel
On purpose? Never. Through carelessness? Rarely, if ever. A diesel nozzle mostly will not go into a petrol car, but the slimmer petrol nozzle goes into the filler of a diesel almost without resistance — so forecourts make this one mistake straightforward, and only in that direction.
It occurs when habit and the vehicle stop matching. Courtesy car, hire car, or a car that's brand new. Households running one of each, petrol and diesel. A forecourt you know, but with its pumps arranged differently. Fuelling up in a rush on the way to Penzance, with a train to catch. Exactly the moment it takes place: after years of driving petrol, someone fills a diesel Volkswagen Passat for the first time. Add a back seat full of kids, a phone call or rain, and habit takes over.
Preventing petrol in a diesel next time you fill up around Treneere
- The label is what counts, so check the pump instead of the colour: in the UK unleaded handles are normally green and diesel black, yet not on each forecourt.
- Plenty of vehicles state the fuel type inside the filler flap or on the cap, and so check there on the first fill in any vehicle you don't know.
- One of each in the household? Mark the key to the diesel — a coloured fob, a sticker — because meaning to remember is not enough.
- It sounds silly and it does the trick: on your first fill in a new or hired car, say "diesel" aloud before you take the nozzle off the petrol pump.
- Mistakes like this are easy to make whilst your mind is on something else, and so the phone goes away.
- Up to a point, a misfuel inhibitor helps: some diesels come with a filler designed to refuse a petrol nozzle, and add-on devices are available for the remainder. Count it as a safety net, then keep checking the pump.
- Spotting it halfway? Stop at once. A thinner mix results from less petrol inside that tank, yet the next step stays the same: do not start the car.
Already put petrol in a diesel in Treneere?
Then, there's just a short order of things. Do not turn the ignition on, and do not start it. If you are still at the forecourt — Tesco or anywhere else — ask the attendants to help you roll the vehicle clear of the petrol pump. Call 0333 366 0103 next, with three answers — your fuel, the rough quantity, and if it's run.
Corrosion and deposits form the trouble with AdBlue, where petrol means lost protection. So if it was AdBlue, say so — and read its own Treneere page.
Treneere petrol in a diesel jobs: why one costs more than another
An honest single price does not exist here: four situations, four separate jobs. Chiefly, your cost shifts with which situation you are in. After that it is the ratio — how much petrol got in against how much that tank takes — and then where the car is and whether our van can reach it safely.
What was put in, how much, and if it has run — three questions our technicians ask before pricing, not after, for exactly that reason. Those replies are what turn a range into one firm number.
About Treneere
Treneere is a suburban area in Cornwall, situated near the coast at an elevation of 37 metres. Treneere lies within a region of gentle slopes and scenic views, close to nearby places like Heamoor and Trythogga. Treneere has a mix of housing types, but terraced housing is predominant in the area. Treneere is located approximately 23.6 miles from the city of Truro, and about 254.7 miles from London.
Fuel drain cover around Treneere and across Cornwall
Petrol in diesel calls around Treneere — part of the TR postcode area — go to vans that also cover the spots about it, Heamoor, Trythogga and Trevarrack among them. The car does not need to come to us: our technicians drain on a forecourt, in a supermarket car park, in a lay-by or on your own driveway.
Treneere: still at the pump?
The best spot there is, then — that's where you are. Keep it turned off, then ring.