Mangrove Green: Petrol in a Diesel Car? How Worried to Be
Provided it has not been started, you can worry less than you probably are. Petrol resting in a diesel tank does nothing to the motor until something pulls it through the system — your ignition priming your pump, the starter, or the drive itself. So the honest answer to the first query anyone around Mangrove Green asks, "have I wrecked it?", is normally no. Leave your motor off and ring Petrol in Diesel — that keeps it that way. The remainder of this page covers what petrol really does to a diesel, how to tell how far it has got, and how to make sure it doesn't happen to you again.
The engine and petrol in a diesel: what goes on
On its way through an engine, diesel has two jobs. It protects to begin with, and after that does it burn. Designed to very fine gaps, the fuel injectors and your pump depend on your diesel moving through them to keep their surfaces from wearing against one another.
The second job petrol does not do at all, and the first it does poorly. Being less viscous than diesel, petrol strips away the protection a fuel system needs, leaving a pump on the blend wearing itself. It's equally made to resist igniting under compression — the reverse of what a diesel needs — which is where you hear the clattering.
Together, those leave the shape of the problem clear. It is movement that causes the harm, not contact. Petrol in the tank is a fuel problem. Whatever a worn pump sheds travels on, borne by the fuel, into the injectors further along, which is why a pump that has worked on that petrol is where a mechanical issue begins.
How serious is petrol in a diesel? Four situations our technicians see around Mangrove Green
The best case there is: filled up, not once started. The petrol is inside the tank and just your tank, and the task is a drain and a flush where the car stands. This is the one scenario that can only truly occur on a forecourt, since anywhere else the vehicle has been driven to get there.
Your ignition switched on, or a short start. Petrol has come out of your tank and got to your filter and your lines, since the fuel system has been bled. Still generally simple: drain, flush, and the filter seen to.
Driven a few miles. Now your pump has spent these miles labouring on diluted fuel. The work is your tank, the fuel lines, the filter and clean fuel through the entire circuit, and how hard the car was driven counts as much as how far. The school run to Cockernhoe Endowed CofE Primary School is one matter. Very different again: a run to St Albans, under 15 miles away, or any mileage on the M1, under 5 miles from Mangrove Green, where the engine never stopped running hard.
Driven on until it complained — knocking, smoke, a lumpy idle, a dead throttle. That is the engine telling you its fuel has stopped behaving like diesel. Whether it is the verge on Mangrove Road, a lay-by or a side street, stop there then leave it. Permanent damage is very unusual when a vehicle is stopped soon, and the fuel drain and flush-through that still go first take care of it.
Petrol in a diesel myths Mangrove Green motorists hear
"Top it up the rest of the way with diesel and it'll be fine" — a myth. It will not. A bigger tank of the same mixture is all you get, because topping up takes out nothing. That advice presumes a diesel fuel system handles petrol by percentage. It does not.
Myth: "A newer diesel can cope with a bit of petrol." If anything, the reverse. At higher pressure, through more precise parts: that is how a modern diesel handles its fuel, and so the lubrication matters more, not less.
This is the one that catches motorists. Myth: "If it starts and drives, there is no harm done." Diesel in a petrol motor usually leaves a motor that will not run: the driver stops, and so does the harm. Nothing seems to have happened when a diesel fed petrol fires up, ticks over and drives away, as it usually does; meanwhile your pump grinds. Fine and running are not the same at all.
Not so: a two-stroke additive lets you to drive home. It is an old workaround, meant for another issue. What petrol has diluted stays weakened, and that petrol stays in your tank anyway.
The next start draws petrol back round your pump out of your lines and your filter, where some of it sits once the engine has been run. That's why a DIY tank drain does not leave you sorted — a myth. Besides, petrol emptied into a can by the road is truly hazardous.
Why petrol in a diesel happens so easily
It's rarely carelessness, and nobody does it on purpose. The forecourt makes it easy: the petrol nozzle is the narrower of the two, and it slides into a diesel filler with almost no resistance, while a diesel nozzle mostly will not go into a petrol motor at all. So the error runs one way.
The moment habit stops matching your car is the moment it takes place. Courtesy car, hire car, or a car that's new. A household with one petrol and one diesel on the driveway. Your ordinary forecourt, its pumps now in a different order. A hurried fill en route to Luton Airport Parkway with a train to catch. Years of petrol cars behind you, a diesel Volkswagen Golf in front of you on the forecourt for its first tank — that's when. With rain, a call arriving, or a car full of children to deal with, the hand simply does what it always has.
How to prevent petrol in a diesel at your next fill-up around Mangrove Green
- Check the pump, not the colour. In the UK unleaded handles are normally green and diesel black, yet not on each forecourt. The label is what counts.
- In a vehicle you don't know, look inside the flap over the filler or at the cap before your first fill: plenty of motors state the fuel type there.
- One of each in the home? Mark the key to your diesel — a coloured fob, a sticker — because intending to remember is not enough.
- Before the nozzle leaves the petrol pump the first time you fill a hired or new vehicle, say "diesel" aloud. Silly, yes, yet it works.
- Thinking about something else is when this becomes an easy mistake to make, and so put your phone away and keep your mind on the petrol pump.
- Up to a point, a misfuel inhibitor helps: some diesels have a filler designed to refuse a petrol nozzle, and add-on devices are available for the rest. Treat it as a safety net, and keep reading the petrol pump.
- Spotting it mid-fill? Stop there and then. A weaker mix follows from less petrol in the tank, yet your next stage remains the same: don't fire it up.
Already put petrol in a diesel around Mangrove Green?
Then the order of things is short. Starting it is out, and so is switching on the ignition. Ask the staff to help you push it clear of the pump if you're still at the forecourt, whether that's Asda or anywhere else. What got in, about how much, and if it's run: tell us those when you ring 0333 366 0103.
If it was AdBlue instead of petrol, say so. That is a different issue — corrosion and deposits instead of lost lubrication — and it has its own page for Mangrove Green.
One petrol in a diesel job in Mangrove Green costs more than another. Why?
Four separate tasks lie behind the four situations above — which is why there's no fair single quote. Mostly, the cost shifts with which situation you are in. Where the vehicle is matters too, and whether a technician can safely reach it, after the ratio of petrol to what that tank takes.
That is why we ask three questions before pricing instead of after: what went in, how much, and if it's run. Those answers are what turn a range into one firm number.
About Mangrove Green itself
Mangrove Green is a small village in Hertfordshire, situated inland at an elevation of around 160 metres. Mangrove Green lies approximately 29 miles north of London and 10 miles east of St Albans, near the villages of Cockernhoe and Tea Green. Mangrove Green has a population of around 559 people, predominantly living in semi-detached houses.
Mangrove Green and Hertfordshire: where our fuel drain cover runs
Mangrove Green waits in the LU postcode area, and our teams that answer petrol in diesel jobs there work the spots around it as well — Cockernhoe, Tea Green and Wigmore among them. The vehicle does not need to move to us: our technicians drain at a forecourt, in a supermarket car park, in a lay-by or on your own driveway.
At the petrol pump in Mangrove Green, still?
Then, you could not be in a better place. Phone, and leave it switched off.