Should You Worry? Petrol in a Diesel Car in Treowen
Probably less than you already are — provided no one has started the vehicle. Petrol sitting in a diesel tank does nothing to the engine till something draws it through the system — the ignition priming the pump, your starter, or the drive itself. So the fair answer to the first question anyone in Treowen asks, "have I ruined it?", is usually no. Leave the engine off then call Petrol in Diesel — that is how you keep it that way. Keep reading for three things: the effect petrol has inside a diesel motor, the signs of how far it has spread, and the way to make sure you never repeat it.
Inside your engine: what petrol in a diesel does
Diesel has two tasks on its way through a motor. It protects to begin with, and only then does it burn. What stops the surfaces inside the high-pressure pump and the injectors from wearing down against one another is the diesel flowing through them — they are made to very fine gaps.
The second task petrol does not do at all, and the first it does poorly. Being less viscous than diesel, petrol strips out the protection a fuel system needs, leaving a pump on that mixture to wear itself. It is equally made to resist igniting under compression — the reverse of what a diesel needs — which is why you get the rattling.
Put those together and the shape of the issue is plain. Contact does not do the damage — movement does. A tank with petrol in it 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 your injectors downstream.
Four scenarios our engineers see around Treowen: how serious is petrol in a diesel?
The best case there can be: filled up, never started. Only that tank has petrol in it, and so the job is emptying that tank and cleaning the system where the car stands. This situation can only really take place on a forecourt: anywhere else, the car got there by being driven.
Started for a second, or only the ignition on. Petrol has come out of that tank and reached the filter and the lines, because the system has been primed. Still normally straightforward: drain, flush, and the fuel filter seen to.
Some miles driven, and your pump has spent each of them running on weakened fuel. Mileage is only half of that; how hard it was driven counts just as much. Either way the work includes the tank, the lines, your filter and fresh fuel through the entire circuit. On the school run to the local primary school, the distance is small. A run as far as Newport, under 10 miles away, is a very different job. So is any miles on the M4, under 10 miles from Treowen, where your engine has been labouring hard the whole time.
Rattling, an uneven idle, smoke, a throttle gone soft: driven till it complained. That is your engine telling you its fuel no longer is behaving like diesel. Whether it is the verge on Kennard Terrace, a lay-by or a side road, stop where you are and leave it. The drain and flush-through still come first, and they sort it out: when a car is pulled over quickly, lasting damage is very unusual.
Stories Treowen motorists hear about petrol in a diesel
Myth: "Fill it the rest of the way with diesel and it'll be fine." It will not. Topping up removes nothing; it gives you a fuller tank of the same mixture. The idea behind the advice — that diesel fuel systems tolerate petrol by percentage — is wrong.
If anything, the opposite is true. Myth: "A modern diesel can cope with a bit of petrol." Finer parts and higher pressure are the way a current diesel runs its fuel, and that makes the lubrication count more, not less.
"It starts, it drives, and so there is no harm" — the myth that trips up most motorists than any other. Any petrol engine fed diesel normally will not run, so the driver stops and the damage stops with them. Feed petrol to a diesel and it usually starts, idles and drives away like nothing happened — all the while its pump is wearing. A running engine does not mean fine.
An outdated workaround for a separate fault lies behind this one. Myth: "Add some two-stroke oil and drive it home." None of what petrol diluted gets put back by it — and afterwards, your tank still holds that petrol.
The next start sends petrol back round your pump from the fuel lines and the filter, where some of it sits after your engine has been run. That is why a DIY tank drain doesn't sort it — a myth. It's also really risky to drain petrol into a can at the roadside.
Why petrol in a diesel occurs at all
On purpose? Never. Through carelessness? Rarely, if ever. 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, whilst a diesel nozzle generally won't go into a petrol vehicle at all. So the slip runs one way.
The moment routine stops matching the vehicle is the moment it happens. Courtesy car, hire car, or a motor that's new. One petrol and one diesel on the drive of the same household. A familiar forecourt with the pumps in a different order. A hurried fill en route to Newbridge with a train to catch. Exactly the moment it occurs: after years of driving petrol, someone fills a diesel Skoda Octavia for the first time. With rain, a call coming in, or children to deal with, the hand just does what it always has.
Preventing petrol in a diesel next time you fill up in Treowen
- Not every forecourt in the UK follows green for unleaded and black for diesel, even if most usually do. Read the pump's label; the colour is only a hint.
- Many motors state the fuel type inside the filler flap or on the cap, so check there on your first fill in a motor you do not know.
- A coloured fob or a sticker on your diesel's key does more than any amount of meaning to remember, in a household with one of each.
- Before the nozzle leaves the petrol pump the first time you fuel a hired or new vehicle, say "diesel" aloud. Silly, yes, but it does the trick.
- Whilst you are thinking about something else, this is an easy mistake to make — so tuck your phone away.
- Add-on devices exist for motors without one, and some diesels are built with a filler that will not take a petrol nozzle. Helpful — but a backstop at best, never a reason to stop checking the label.
- Less petrol means a thinner blend, and so stop the moment you notice — while remembering that your next stage is unchanged. It is still not to crank it.
Petrol already in a diesel around Treowen? Begin here
Then, there is only a short order of things. Starting it is out, and so is switching on your ignition. Still on the forecourt, at Texaco or anywhere else? Ask the staff to help you push the car away from the pump. Then phone 0333 366 0103 and tell us what was put in, roughly how much, and whether it has run.
Corrosion and deposits form the issue with AdBlue, whereas petrol means lost protection. So if it was AdBlue, say so — and read its own Treowen page.
Why one petrol in a diesel task in Treowen costs more than another
The four situations above are four separate jobs, so no single quote for this would be fair. What shifts the cost is mostly which of them you are in. Two things follow that: the petrol that got in as a proportion of what the tank takes, then the spot the car is in and whether a van can reach it safely.
That's why our technicians ask three questions before pricing instead of after: what got in, how much, and if it has run. A range becomes a straight figure when those answers are in.
About Treowen
Treowen is a suburban area situated on the riverside in Caerphilly, with a mix of terraced housing and a population of around 2159 residents. Treowen sits at an elevation of 173 metres, close to the nearby communities of Crumlin, Rhiw, and Millbrook. Treowen is located near the city of Newport, which is approximately 8.9 miles away. Treowen's riverside setting provides a distinctive character to the area.
Treowen and Caerphilly: where our fuel drain cover runs
Petrol in diesel call-outs in Treowen — part of the NP postcode area — go to teams that likewise cover the locations around it, Crumlin, Rhiw and Millbrook among them. We drain wherever the car is — your own driveway, a lay-by, a supermarket car park, a forecourt — so it never needs to come to us.
At the petrol pump in Treowen, still?
Then you're in the best place there can be. Switched off it remains; then phone.