--- title: AdBlue in a Diesel Tank Penycwm: Explained canonical: https://www.petrolinadieselcar.co.uk/adblue-in-diesel/penycwm-pembrokeshire/ location: Penycwm county: Pembrokeshire latitude: 51.867440 longitude: -5.124710 service: AdBlue in a Diesel Tank updated: 2026-10-27 --- # How It Occurs and How to Avoid It: AdBlue in a Diesel Tank in Penycwm If AdBlue is already in your diesel tank, stop reading for a moment: leave the motor and the ignition off and ring 0333 366 0103. Normally, when your engine has not run, it is drained and fully cleaned where your car sits around Penycwm. Reading in advance? In that case what follows explains why it happens and what to stop it ever happening. ## Why does AdBlue in a diesel motor need its own filler? No single fluid but two: that's what many newer diesels around Penycwm and Brawdy run, with diesel feeding the motor. AdBlue goes to the exhaust, where it is sprayed into the gas to fresh it, and it lives in a tank of its own. There's a filler on every tank. Under one flap, side by side: that's the layout on a lot of cars. On others, AdBlue's filler sits beneath the bonnet or in your boot instead. Diesel gets filled on every forecourt visit, again and again. Far less often, the AdBlue side gets topped up — normally from a bottle, by someone working out where it goes. It's in that gap that the error happens. ## Penycwm: how AdBlue in your diesel tank happens Carelessness rarely explains it. Instead is three things lining up together. On a drive off A487 before work, or in the car park outside Duke Of Edinburgh heading home: that is where the rushed top-up happens. Why the rush? As AdBlue gets low your car warns you, and if it's gone, limp mode kicks in. Then the vehicle is strange. A hire car, a new car or a company car puts the fillers where your last one did not, and your hand gets to for the cap it would have used on the old one. Third, the bottle fits: a diesel filler or AdBlue one, it slides in as easily, and once the pour starts, no part halts it. Newgale or the middle of Penycwm: it is the same few seconds either way. ## The AdBlue filler and the diesel filler: telling them apart Look at these before pouring, on a forecourt around Penycwm or a drive over in Trefgarn Owen. Seconds, no more. - The cap. The AdBlue cap is regularly blue, or marked "AdBlue". Your diesel cap usually is not. Read it rather than going by where it sits. - On many motors, size gives it away: AdBlue has the smaller filler neck. - The flap. Look inside the fuel flap for a label. Plenty of cars say there which fuel goes where. - The handbook shows where it lives when the filler is not next to the diesel cap: the boot, or under the bonnet. - Collecting a hire or company car, say at the car park at Haverfordwest? Check with whoever drove the vehicle last before leaving, not once the light comes on. ## AdBlue top-ups that never reach the diesel tank Anywhere across Pembrokeshire the light comes on, here is a routine for that day. - Park and switch off. Not on a slope, not with the engine running, and not in a rush on the side of Newgale Hill. - Locate the AdBlue filler, read the cap, and speak the word "AdBlue" out loud while you unscrew it. It sounds silly. It does the trick. - Both behind one flap? Then make sure the lid on your diesel filler is still closed ahead of lifting the bottle. - Using the bottle's own spout, tip slowly — and stop when it is full or the bottle is empty. - Shut the cap, and check again — making sure your diesel cap stayed shut throughout. Only then, start the vehicle. Stop there if you find, at step two or three, that you have already poured into the diesel side. Stage five is out. ## AdBlue in your diesel tank already, in Penycwm? Do not start the engine: that is how the short order of things starts. On many diesels the ignition alone runs the fuel pump, so don't switch the car on. Thinning it with extra diesel fails, because AdBlue sinks to the bottom instead of mixing — and that is where your fuel is drawn from. Ask the staff to help push the car away from the pump if you're on a forecourt — the the nearest petrol station, the another forecourt nearby or anywhere else. At home around Penycwm? Then your car stays where it is. If the motor has already run, stop as soon as it is safe and switch off. Come off the M4 — under 50 miles out of Penycwm — at the first junction. A short hop across Penycwm is a smaller job than a run towards St Davids, under 10 miles away, and so tell us about how far it went. ## Penycwm: what happens when our engineers turn up By the local primary school, close to Pointz Castle or on your own drive: wherever your car has stopped, our technicians come to it. Both the work and our price rest on three answers — which liquid, which amount, and whether it has run — so we ask. During the call itself, you are told our price — before anything else. After that: draining, then a thorough flush of the whole system. More than with petrol, it matters with AdBlue: crystals build up, some metals corrode, and nothing washes out on its own, however long it is left. Filter flushed or, where it must be, replaced; fresh diesel in; then a check of your vehicle. The engine is fired up next and tested to make sure it runs properly, all before our technicians go. If the engine has not run, most jobs take about half an hour once we are there, using pumps that are safe on a busy forecourt and quiet enough to use outside a house at night. You pay on the day, with nothing upfront, and get a VAT invoice and an engineer report for your insurer. Many insurance policies include misfuelling cover, and so it's worth checking yours whilst we're on the way. ## About Penycwm Penycwm is a small coastal village in Pembrokeshire, situated near the popular beaches of Newgale and the surrounding countryside. Penycwm sits at an elevation of 93 metres, overlooking the coastline and within a short distance of the nearby city of St Davids. Penycwm has a population of around 520 people, predominantly living in semi-detached housing. Penycwm is close to other nearby places such as Wood and Rhydygele, and is about 215 miles from London. ## AdBlue drains in Penycwm and across Pembrokeshire Throughout SA postcodes, our teams that cover Penycwm — a coastal village — work the nearby places too, Rhydygele and Wood included. Give a postcode beginning SA62 6, and our van arrives quickest. The vehicle doesn't need to move. The drain takes place on the spot, be it a driveway, a street by St. Teilo's Church, Llandeloy, or a lay-by on the way to the green space at the edge of the village. Ring and ask instead of guessing if you are close to a border, or somewhere hard to explain, like the back of Tre-Maen-Hir Standing Stone. ## Penycwm people: the short version Before you tip, read the cap. AdBlue in the diesel tank regardless? Leave it off and ring 0333 366 0103; Petrol in Diesel drains it where it stands, throughout Pembrokeshire.