Should You Worry? Petrol in a Diesel Car in Graigwen
Likely less than you already are — provided no one has started it. Until your ignition primes your pump, the starter cranks, or the car is driven, petrol in a diesel tank just rests there and does no harm. Which means the honest reply to that first Graigwen question — "have I wrecked it?" — usually no. Petrol in Diesel is who to phone, with your motor kept off, so it stays that way. What petrol actually does to a diesel, how to judge how far it has travelled, and how to stop it from happening again: that is the remainder of this page.
Petrol in a diesel: what does it do to the engine?
On its way through a motor, diesel does two jobs. It ignites, and before it ignites it protects. Designed to extremely fine clearances, the injectors and your pump rely on the diesel moving through them to stop their surfaces wearing against one another.
Of those two jobs, petrol handles the first badly and the second never. It is thinner than diesel and strips away the protection your fuel system rests on, so a pump running on a petrol blend is a pump wearing itself. And petrol is designed to resist igniting under compression, which is the reverse of what a diesel needs from its fuel. That's where the knocking comes from.
Put those together and the shape of the trouble is plain. The harm is done by circulation, not by contact. Where that petrol is only inside that tank, it is an issue of fuel, nothing more. Whatever a worn pump sheds goes on, borne by the fuel, into the fuel injectors further along, which is why a pump that has been working on the petrol is where a mechanical problem starts.
Four scenarios we see around Graigwen: how bad is petrol in a diesel?
Fuelled up, not once started. The best case there can be. On a forecourt, and genuinely only there, the petrol is still limited to your tank — because anywhere else the car was driven to get to it. The task is emptying and rinsing on the spot.
Started for a moment, or just the ignition on. Once primed, your system has drawn petrol from the tank as far as your filter and the lines. Drain, flush, see to your filter: still usually easy.
Driven a few miles. Now the pump has spent these miles running on weakened fuel. Miles is only half of that; how hard it was driven counts equally. Either way the work includes that tank, your lines, the fuel filter and fresh fuel through the whole system. Driving the kids to the local primary school is one sort of trip. Getting as far as Cardiff, under 15 miles away, makes a very different task — as does any mileage on the M4, under 10 miles from Graigwen, with the engine running hard all the way.
Driven till it complained. Rattling, a ragged idle, smoke, a throttle that has gone soft. What you are hearing is your motor signalling fuel that no longer behaves like diesel. Leave it where it has stopped: a lay-by, a quiet street, the verge on Llwynmadoc Street. Long-term damage is very rare if a vehicle is stopped quickly, and the fuel drain and flush-through that still come first sort it out.
Graigwen people and that petrol in a diesel myths they hear
It will not be fine. The myth: "Fill it the rest of the way with diesel and it will be." Topping up removes nothing; it gives you a bigger tank of the same mixture. The idea behind that advice — that diesel fuel systems accept petrol by percentage — is wrong.
Not so: a newer diesel copes with a bit of petrol. Rather, the opposite. More precise parts and higher pressure are the way a newer diesel runs its fuel, and that makes the protection count more, not less.
This is the one that catches motorists. Myth: "If it starts and drives, there is no harm done." The motorist of a petrol motor fed diesel normally stops, since it will not run, and the damage stops there. Whilst your pump grinds, a diesel fed petrol usually starts, ticks over and drives away as if nothing has happened. Fine and running are not the same thing.
An old workaround for a different problem lies behind this one. Myth: "Add some two-stroke oil and drive the car home." The petrol is still in your tank after that, and what it has weakened is not put back.
Myth: "Drain the tank yourself and you're sorted." After your engine has been run, some of the petrol is no longer in your tank: it's in the fuel filter and the lines, and it goes right back through the pump at your next start. On top of that, petrol emptied into a can by the road is truly dangerous.
Petrol in a diesel: how does it 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 won't fit a petrol motor. That's how the forecourt makes it easy.
When routine and the vehicle stop matching, it takes place. Hire cars, courtesy cars, and vehicles that are new to you. One petrol and one diesel on the drive of the same household. A well-known forecourt with the pumps in a different order. A train to catch, and a rushed fill en route to Pontypridd. Precisely the moment it happens: after years of driving petrol, someone fills a diesel Volkswagen Golf for the first time. Throw in a back seat full of kids, a phone call or rain, and habit takes over.
How to avoid petrol in a diesel on your next fill-up in Graigwen
- Green for unleaded and black for diesel is normal in the UK — but not on every forecourt. Trust the label on the petrol pump, not the colour.
- Check the filler flap. Plenty of motors state the fuel inside the flap or on the cap. Look at it on the first fill in a vehicle you do not know.
- One of each in the house? Mark your key to the diesel — a coloured fob, a sticker — since meaning to remember isn't enough.
- It sounds daft and it does the trick: on your first fill in a new or hired car, say "diesel" aloud before you lift the nozzle off the petrol pump.
- Put your phone away. This is an easy mistake to make while you are thinking about something else.
- A misfuel inhibitor helps, up to a point. Some diesels come with a filler built to reject a petrol nozzle, and add-on devices are available for vehicles without one. They are a backstop, not a reason to stop checking the pump.
- As soon as you notice, stop: less petrol inside your tank means a weaker mix. What to do next doesn't change, though — still don't fire it up.
Put petrol in a diesel in Graigwen already?
Then the order of things is short. Leave it unstarted, with your ignition switched off as well. The staff at the forecourt — whether at Asda itself or wherever you filled up — will normally help push it clear of the pump if you ask. Then call 0333 366 0103 and tell us what was put in, roughly how much, and whether it's run.
Corrosion and deposits form the trouble with AdBlue, whereas petrol means lost protection. So if it was AdBlue, say so — and read its own Graigwen page.
One petrol in a diesel job around Graigwen costs more than another. Why?
There's no honest single quote for this, because the four scenarios above are four different jobs. Chiefly, the cost shifts with which situation you're in. Where the vehicle is matters too, and whether our van can safely reach it, after the proportion of petrol to what that tank takes.
Three queries come first, before any quote, rather than after — what was put in, how much, has it run — and this is the reason. Given the answers, there is a straight figure rather than a range.
About Graigwen, for a moment
Graigwen is a suburban area situated on the riverside in Rhondda Cynon Taf, with a mix of terraced housing and local amenities. Graigwen sits at an elevation of 103 metres, close to the nearby communities of Penygraigwen and Pwll-Gwaun. Graigwen is located near the town of Pontypridd and is approximately 11 miles from Cardiff, the capital city of Wales. Graigwen has a population of around 5346 residents.
Graigwen and Rhondda Cynon Taf: where our fuel drain cover reaches
Graigwen waits in the CF postcode area, and the teams that answer petrol in diesel jobs there work the spots near it as well — Penygraigwen, Pwll-Gwaun and Pontypridd among them. A forecourt, a supermarket car park, a lay-by or your own drive are all places our engineers drain, and your vehicle doesn't need to move to us.
Graigwen: still at the pump?
No position is better: that is where you now are. Phone, and leave it switched off.