--- title: AdBlue in a Diesel Tank Llanfaes? Read This canonical: https://www.petrolinadieselcar.co.uk/adblue-in-diesel/llanfaes-powys/ location: Llanfaes county: Powys latitude: 51.944880 longitude: -3.405170 service: AdBlue in a Diesel Tank updated: 2026-10-01 --- # How It Happens and How to Avoid It: AdBlue in a Diesel Tank in Llanfaes AdBlue already in your diesel tank? Then set this page aside a moment, keep the ignition and engine off, then ring 0333 366 0103. Caught before the engine runs, it's generally a drain and a thorough flush, done where the car is around Llanfaes. If you're reading before it has happened, the rest of this page is about why it happens and how to make sure it doesn't. ## AdBlue in a diesel motor: two tanks, two fillers Diesel feeds your engine — yet many current diesels seen around Llanfaes and Pontwilym hold a second fluid as well. Stored in a tank of its own, AdBlue is fed into your exhaust stream and cleans it. Each tank comes with a filler of its own. Other cars keep the AdBlue filler in your boot or under the bonnet; a lot of others place the two together under one flap. Topping up your diesel side at the petrol pump goes on constantly. Rarely filled, AdBlue usually comes from a bottle, poured by someone who must stop and think what filler it needs. The error lives in that gap. ## How AdBlue in the diesel tank happens in Llanfaes Seldom is it carelessness: usually three things line up. The warning comes first. As AdBlue runs low your car tells you, and if it runs out completely, the car drops into limp mode. So the top-up is done in a hurry: on a driveway off Newgate Street before work, or in the car park at The Drovers Arms on the way home. Next, your hand goes for the cap it would have used on the old vehicle — since a hire car, a new vehicle or a company car puts the fillers where your last one did not. And the bottle fits. A bottle with a spout goes into a diesel filler as easily as an AdBlue one, so nothing stops the pour after it has started. The same few seconds settle it, in the middle of Llanfaes or out in Brecon. ## How to tell the AdBlue filler from the diesel one A few seconds is all the checks take — so check them before you pour anything, on a driveway in Fenni-fach or a forecourt in Llanfaes. - Blue and marking: an AdBlue cap is frequently blue, or says "AdBlue", where a diesel cap normally does not. Go by the cap, not where it sits. - Look at the size: the smaller filler neck is, on plenty of cars, the AdBlue one. - The flap. Look inside the fuel flap for a label. Many motors say there which fuel goes where. - In the boot or under the bonnet: that's where your filler sits if it is not by the diesel cap, and the handbook says which. - Collecting a hire or company car, say at the car park at the nearest station? Check with whoever drove the car last before leaving, rather than once the light goes on. ## Topping up AdBlue without it reaching the diesel tank For the day the light appears — wherever it is across Powys — a simple routine to use. - Turn off after you park — flat ground, motor stopped, and never rushed by Blackfriars Court at the roadside. - Find the AdBlue filler and read the cap. Say "AdBlue" out loud as you unscrew it. It sounds silly and it works. - If both sit under one flap, check the diesel cap is still closed before you lift the bottle — and leave the vehicle on. - Gently is best, through the bottle's own spout, till it is full or the bottle is empty. - Close the cap and check once more. Make sure your diesel cap was never opened. Only then start your car. Find at the second or third step that the bottle went into the diesel filler? That is where you stop. Don't go on to stage five. ## Llanfaes: already put AdBlue in the diesel tank? Then the order of things is short. Do not start the engine. The fuel pump starts on many diesels the moment the ignition goes on — so leave it off. Thinning it with more diesel fails, because AdBlue settles to the bottom instead of mixing — and that is where the fuel is pulled from. The attendants at Gulf, Morrisons or any forecourt will normally help to push the car clear if asked. If you're on your own driveway in Llanfaes, leave the car where it sits. When the motor has run already, pull over somewhere safe then turn it off. Leave the M4 — under 50 miles out of Llanfaes — at the first junction. About how far did it go? Hopping across Llanfaes is smaller a job than a run of under 50 miles towards Newport, and so tell us. ## What occurs when our engineers turn up around Llanfaes Anywhere your car came to rest, whether outside the local primary school, beside Church of St David or at home, the van comes to it. Our technicians ask what went in, about how much, and whether it has run, because those replies determine the work and our price. Nobody sets off until you have heard our price by phone. After that: draining, then a full flush of the whole system. AdBlue crystallises and is corrosive to some of the metals in a fuel system, and so it doesn't wash out on its own — which is why that matters more here than with petrol. The filter cleaned or, where it must be, swapped; fresh diesel in; and then a test of the car. We don't go until it has been fired up and is running smoothly. If the engine has not run, most jobs take about half an hour once we're there, using pumps that are fine on a working forecourt and quiet enough to use outside a house at night. Your insurer usually wants an engineer's report and the VAT invoice, and you get both at the end. Payment is on the day, with no deposit. It's worth looking at your policy as the van travels to you: misfuelling cover comes with plenty of policies. ## About Llanfaes and where it is Llanfaes is a suburban area situated on the riverside in Powys, Wales, with a mix of terraced housing and a population of around 1779 residents. Llanfaes sits at an elevation of 137 metres, near the towns of Brecon and Pendre, and is approximately 30 miles from Newport. Llanfaes is located in a scenic part of Wales, with the Uplands nearby, and is about 143 miles from London. ## Llanfaes and Powys: AdBlue drains across the area Being a residential suburb, Llanfaes shares its vans nearby areas — Uplands, Pendre — all the way through LD postcodes and the wider area beyond. Quote a postcode beginning LD3 8, and our van arrives fastest. Moving your car isn't needed. The drain happens on the spot, whether a drive, a road by Kensington Baptist Church, or a lay-by on the way to Brecon Golf Course. Tricky to explain, like the back of Site of Brecon County Grammar School for Boys? By a border? Checking beats guessing, and so ring. ## Llanfaes motorists: the short version First, the cap; then, the pour. AdBlue in your diesel tank regardless? Leave the vehicle switched off then phone 0333 366 0103; Petrol in Diesel empties it on the spot, throughout Powys.