Bethel: Petrol in a Diesel Car? How Worried to Be
Less than you likely are, if it hasn't been started. Petrol resting in a diesel tank does nothing to your motor until something draws it through the system — the ignition priming the pump, your starter, or driving on its own. So the truthful answer to the first question everyone around Bethel asks, "have I wrecked it?", is normally no. Petrol in Diesel is who to ring, with the engine left off, so it stays that way. Below, this page sets out what petrol really does inside a diesel, how far it may have gone, and how to stop it happening to you a second time.
Petrol in a diesel: what does it do to the engine?
Passing through an engine, diesel is doing two things at the same time. It lubricates first, and after that does it burn. Designed to very fine tolerances, the injectors and your pump rely on your diesel moving through them to stop their surfaces wearing against one another.
Petrol handles the first job poorly and the second not at all. 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 runnier than diesel, it strips out the protection the system rests on, and any pump working on that blend is wearing itself.
Together, those make the shape of the trouble plain. The damage is done by movement, not by contact. Where the petrol is only inside your tank, it is a fault of fuel, nothing more. 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 further on.
Four scenarios we see in Bethel: how bad is petrol in a diesel?
Filled but never started — the best it gets. On a forecourt, and really only there, the petrol is still limited to the tank — because everywhere else the vehicle was driven to reach it. The job is draining and rinsing on the spot.
A moment's running, or just the ignition on. The fuel system has been bled, and so petrol has left the tank and got to your filter and the fuel lines. Usually nothing more than clearing, flushing and seeing to your filter, so still easy.
Driven a couple of miles. Now the pump has spent these miles running on weakened fuel. The work is that tank, the lines, the filter and clean fuel through the entire system, and how hard your car was driven counts as much as how far. On the school run to the local primary school, the miles is short. Very different again: a run to Bangor, under 10 miles away, or any miles on the Moreton Spur, under 50 miles from Bethel, where the engine kept running hard.
Rattling, a ragged idle, smoke, a throttle gone soft: driven till it complained. The fuel isn't acting like diesel any more, and the engine is saying so. Pull up where you are — on the verge on Stryd Bellaf, at the kerb, down a side road — and don't move it again. Lasting damage is very rare if a car is pulled over soon, and the fuel drain and flush-through that still come first sort it out.
Myths Bethel drivers hear about petrol in a diesel
Myth: "Fill it the rest of the way with diesel and it'll be fine." It will not. Nothing comes out when you top up — the tank just holds more of the same mixture. A diesel fuel system doesn't tolerate petrol by percentage in the way that advice presumes.
Myth: "A newer diesel can cope with a bit of petrol." If anything, the opposite. At higher pressure, through finer components: that is how a current diesel moves its fuel, and so the lubrication matters more, not less.
The myth that catches people off guard: if it starts and drives, it must be unharmed. The driver of a petrol motor fed diesel normally has no choice but to stop, because it will not run, and the harm stops there. Feed petrol to a diesel and it generally starts, idles and pulls away like nothing happened — all while its pump is wearing. Being able to run is not proof of being fine.
An outdated workaround for a separate fault lies behind this one. Myth: "Add some two-stroke oil and drive it home." It doesn't put back what petrol has diluted, and the petrol is still inside your tank later on.
If your engine has been run, part of that petrol is in the filter and your lines, not that tank — and your next start sends it right back through your pump. So the myth "drain that tank yourself and you are sorted" does not stand up. It's also really risky to drain petrol into a can by the kerbside.
How does petrol in a diesel occur?
It's seldom carelessness, and no one does it on purpose. One way only, since of the nozzles: the narrower petrol one slides 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 easy.
The moment habit stops matching the vehicle is the moment it takes place. Hire cars, courtesy cars, and vehicles that are new to you. A household with one petrol and one diesel on the driveway. Your usual forecourt, its pumps now in a different order. A hurried fill on the way to Llanfairpwll with a train to catch. A new-to-you diesel BMW 3 Series, its first fuelling, and a motorist used to petrol: exactly when it happens. Throw in a back seat full of kids, a phone call or rain, and the hand wins.
How to prevent petrol in a diesel at your next fill-up around Bethel
- Read the pump, not the colour. In the UK unleaded handles are usually green and diesel black, yet not on every forecourt. The label is what counts.
- The first fill in an unfamiliar motor is the time to check your filler flap — inside it, or on the cap, plenty of vehicles state which fuel to use.
- A coloured fob or a sticker on the diesel's key achieves more than any amount of meaning to remember, in a household with one of each.
- Before the nozzle comes off the petrol pump the first time you fill a hired or new vehicle, say "diesel" out loud. Silly, yes, but it does the trick.
- Put the phone away. This is an easy mistake to make while you're thinking about something else.
- Add-on devices are available for motors without one, and some diesels come with a filler that will not take a petrol nozzle. Helpful — but a backstop only, never a reason to stop checking the label.
- The moment you realise, stop: less petrol inside your tank means a thinner mixture. What to do next does not change, though — still don't start it.
Bethel: already put petrol in a diesel?
Short and simple, then, is the order of things. Leave it unstarted, with your ignition switched off as well. Yet on the forecourt, at Essar or anywhere else? Ask the attendants to help you roll the vehicle clear of the pump. Then call 0333 366 0103 and tell us what went in, about how much, and if it has run.
If it was AdBlue rather than petrol, say so. That's a different fault — corrosion and deposits instead of lost protection — and it has its own page for Bethel.
Bethel petrol in a diesel tasks: why one costs more than another
The four situations above are four separate jobs, so no single price for this would be honest. Which of them you are in is mostly what shifts your cost. Where the car is matters too, and whether a technician can safely reach it, after the ratio of petrol to what your tank takes.
Before any quote, not after, come three queries: your fuel that was put in, the quantity, and whether it has run. That is why. The answers turn a range into a straight figure.
About Bethel
Bethel is a small village in Gwynedd, situated on the coast of northwest Wales, with a mix of detached housing and scenic views. Bethel sits at an elevation of 91 metres, overlooking the surrounding countryside and close to the nearby cities of Bangor and Caernarfon. Bethel is part of a network of small villages and hamlets, including Saron, Tan-y-maes, and Llanddeiniolen, that make up the local community. Bethel has a population of around 792 residents, who enjoy the village's quiet atmosphere and coastal location.
Across Gwynedd and around Bethel: fuel drain cover
Petrol in diesel jobs around Bethel — part of the LL postcode area — go to teams that likewise cover the spots about it, Saron, Tan-y-maes and Llanddeiniolen included. A forecourt, a supermarket car park, a lay-by or your own drive are all locations our engineers work, and the vehicle doesn't need to move to us.
At the petrol pump around Bethel, right now?
Then, you could not be in a better position. Ring, and leave it turned off.