--- title: Explained: AdBlue in a Diesel Tank Lon-las canonical: https://www.petrolinadieselcar.co.uk/adblue-in-diesel/lon-las-swansea/ location: Lon-las county: Swansea latitude: 51.662260 longitude: -3.874440 service: AdBlue in a Diesel Tank updated: 2026-10-03 --- # How It Occurs and How to Prevent It: AdBlue in a Diesel Tank in Lon-las AdBlue already in your diesel tank? In that case put this page down for now, keep your ignition and motor off, then call 0333 366 0103. A drain plus a thorough flush, done right where the car sits around Lon-las, is normally all it needs when caught before your engine runs. Reading before the event? Then what follows covers why it happens and what to prevent it ever happening. ## Why does AdBlue in a diesel motor need its own filler? Many modern diesels around Tair-ysgol, as well as Lon-las, carry on two liquids; your engine gets only your diesel. Your exhaust, not the motor, is where AdBlue goes: sprayed into the fumes to clean them, from its own tank. Each tank comes with one filler of its own. Other cars keep the AdBlue filler in the boot or under the bonnet; plenty more place both side by side under one flap. Diesel goes in at every filling station call-out, week in, week out. Far less often, the AdBlue side is topped up — normally from a bottle, by someone working out where it goes. The slip lives in that gap. ## How does AdBlue in your diesel tank take place around Lon-las? Carelessness rarely explains it. Instead is three things lining up together. First, the warning. Low AdBlue triggers a message from the vehicle, and letting it run out means limp mode — hence a hurried top-up, maybe before work off Birchgrove Road, or at the pub in the village on the way home after work. Unfamiliar cars come second, too. Hire cars, new motors and company cars place their fillers differently, and habit reaches for the cap used on the old one. Lastly, the bottle fits: diesel filler or AdBlue filler, it goes in as easily, and after the pour begins, nothing halts it. The same few seconds settle it, in the middle of Lon-las or out in Llwynbrwydrau. ## How to tell the AdBlue filler from the diesel one A couple of seconds is all the checks take — so check them before you tip anything, on a driveway in Heol Las or a forecourt in Lon-las. - Where it sits misleads; the cap doesn't. AdBlue caps are often blue or carry the word "AdBlue" — diesel caps normally don't. - The size. On plenty of motors the AdBlue filler neck is the smaller of the two. - Open the flap and check for a label — plenty of motors show which belongs in each filler right there. - The handbook says which it is when your filler isn't next to the diesel cap: the boot, or under the bonnet. - The person who drove it last. On a hire or company car collected from somewhere like the car park at Llansamlet, ask before you leave, not when the light comes on. ## How to top up without AdBlue in the diesel tank When the light comes on, anywhere in Swansea, use this routine. - Stop on level, engine off, with time to spare — not hurried on the side of Clos Y Chwarel. - Locate the AdBlue filler, check the cap, and say the word "AdBlue" aloud while you unscrew it. It sounds daft. It works. - The diesel cap remains on. When both sit under a flap, confirm it's closed before the bottle comes up. - Finish when your tank is topped up or the bottle is empty; until then, tip slowly using the built-in spout. - Before you start the vehicle, shut the cap and check again that the diesel cap never opened off. Spot at stage two or three that it's already gone into your diesel side? So stop right there. Do not go on to step five. ## Already put AdBlue in the diesel tank around Lon-las? Then the order of things is short. Don't start the engine. Do not switch your ignition on; on plenty of diesels that alone runs the fuel pump. AdBlue does not mix with diesel — it sinks to the bottom of the tank, where the fuel is drawn from — so do not top up with diesel to dilute it. The staff at the nearest petrol station, Texaco or another forecourt will usually lend a hand pushing the car clear when you ask. Your own drive in Lon-las is where it stays. When the motor has been run already, pull over somewhere safe then switch it off. Leave the M4 — under a mile out of Lon-las — at the first junction. Tell us about how far it went: a run towards Swansea, under 5 miles away, is a bigger job than a short hop across Lon-las. ## Lon-las: what happens when our engineers get there By the local primary school, near Guru Nanak Sikh Community Centre or on your own driveway: wherever the vehicle has stopped, our technicians come to it. Our engineers ask what got in, about how much, and if it's run, because the replies determine the work and the price. No one heads out before you've heard the price by phone. Then the tank is cleared and the fuel system rinsed thoroughly. More than with petrol, it counts with AdBlue: the crystals build up, certain metals corrode, and nothing clears away on its own, no matter how long it is left. Testing is at the end: before that, fresh diesel goes in, and the filter is cleaned or replaced if necessary. After that we fire it up and confirm it runs smoothly before we leave. Using pumps safe on a working forecourt and quiet enough for use outside a house at night, most jobs where your motor has not run take about half an hour once our engineers are there. You pay on the day, with nothing upfront, and get a VAT invoice and an engineer report for your insurer. Before we get there, take a look at your policy; plenty include cover for misfuelling. ## About Lon-las and where it is Lon-las is a suburban area situated on the outskirts of Swansea, with a mix of semi-detached housing and a population of around 3965 residents. Lon-las sits at an elevation of 76 metres, close to the coast and near neighbouring communities such as Llwynbrwydrau and Peniel Green. Lon-las is located approximately 4.1 miles from Swansea city centre, making it a convenient residential area for those working in the city. Lon-las is also part of the wider Swansea urban area, with easy access to local amenities and services. ## AdBlue drains across Swansea, Lon-las included Being a residential suburb, Lon-las shares its vans surrounding areas — Peniel Green, Birchgrove — all the way through SA postcodes and the wider area beyond. Our van gets to you fastest with a postcode starting SA7 9. The car doesn't need to shift. Anywhere it sits — near Peniel Green Church, in a layby heading to Primrose Park, at home — that's where it is emptied. Ring and ask rather than guessing if you're close to a border, or somewhere hard to explain, like the back of Scott's Pit. ## The short version for Lon-las motorists Read the cap before you tip. AdBlue in your diesel tank regardless? Keep the vehicle off then call 0333 366 0103; Petrol in Diesel empties it on the spot, throughout Swansea.