--- title: AdBlue in a Diesel Tank Mynydd-bach? Read This canonical: https://www.petrolinadieselcar.co.uk/adblue-in-diesel/mynydd-bach-swansea/ location: Mynydd-bach county: Swansea latitude: 51.661250 longitude: -3.950520 service: AdBlue in a Diesel Tank updated: 2026-10-16 --- # AdBlue in a Diesel Tank in Mynydd-bach: How It Occurs and How to Prevent It If AdBlue is already in your diesel tank, stop reading for a moment: leave the engine and your ignition off then call 0333 366 0103. In Mynydd-bach, finding it before your engine runs usually leaves draining and a thorough flush where it stands. If you are reading before it has happened, the rest of this page is about why it occurs and how to make sure it doesn't. ## Two fillers, two tanks: AdBlue in a diesel motor Not one fluid but two: that's what plenty of modern diesels around Mynydd-bach and Tre-boeth run, with diesel for your motor. Its own tank keeps it, and from there it goes to the exhaust, and there spraying treats the gas. Separate tanks, different fillers. Other motors put the AdBlue filler in the boot or under the bonnet; plenty more have the two together under one flap. Filling your diesel side at the petrol pump goes on constantly. Far less often, the AdBlue side is topped up — mostly from a bottle, by a person working out where it goes. It's in that gap that the mistake lives. ## Mynydd-bach: how AdBlue in the diesel tank happens Carelessness seldom explains it. What does is three things lining up together. On a drive off Llangyfelach Road before work, or in the car park outside Welcome Inn on the way home: that is where the rushed top-up takes place. What is the reason for the rush? As AdBlue gets low the car tells you, and if it's empty, limp mode follows. Unfamiliar cars come second, as well. Hire cars, new cars and company vehicles place their fillers in new places, and the hand reaches for the cap it used on the old one. Nothing stops the tip once it has started, since a bottle with a spout goes into a diesel filler as easily as an AdBlue one. The bottle fits. Whether it occurs in Tirdeunaw or the middle of Mynydd-bach, it's the same few seconds. ## The AdBlue filler and your diesel filler: telling them apart Be it a Mynydd-bach forecourt or a drive over in Llangyfelach, spend a few seconds on these before any is poured in. - Where it sits misleads; the cap doesn't. AdBlue ones tend to be blue or bear the name "AdBlue" — diesel caps normally don't. - The size. On many motors the AdBlue filler neck is the smaller of the two. - A label inside the fuel flap often shows which fuel goes where, on plenty of motors. Check for it. - In the boot or under the bonnet: that is where your filler sits if it's not by the diesel cap, and the handbook says which. - The previous driver knows. Check as you collect a hire car or fleet car — at Llansamlet's car park, perhaps — rather than when the warning appears. ## Topping up AdBlue without it reaching your diesel tank For the day the warning comes on — anywhere you are around Swansea — a routine to follow. - Pull in somewhere level, motor off, with time in hand — not hurried on the side of Creswell Road. - Say "AdBlue" out loud as you unscrew the cap, once you find the AdBlue filler and read it. Daft, yes, but it does the trick. - If both sit under one flap, check the diesel cap is still closed before you lift the bottle — and leave the car on. - Finish when that tank is topped up or the bottle runs dry; until then, pour gently using the built-in spout. - Only then, start the vehicle: close the cap, check once more, and make sure your diesel cap was never opened. Find at stage two or three that it's already gone into the diesel side? So stop right there. Leave out step five altogether. ## AdBlue in your diesel tank already, around Mynydd-bach? Don't start your engine: that's how the short order of things begins. Don't switch the ignition on; on many diesels that alone runs the fuel pump. Diluting it with extra diesel fails, because AdBlue sinks to the base rather than blending — and that's where your fuel is pulled from. The staff at Texaco, Murco or any forecourt will usually help to push the car away when you ask. Leave it where it is if you are on your own driveway around Mynydd-bach. Already run? Pull over once it's safe, then turn off. Mynydd-bach lies under a mile from the M4; on it, take the next exit. Tell us roughly how far it went: a run towards Swansea, under 3 miles away, is a bigger job than a short hop across Mynydd-bach. ## When our engineers turn up in Mynydd-bach, what occurs? Wherever the car has stopped, be it outside the local primary school, near Penlan Leisure Centre or at home, our van travels to it. What fluid got in, the quantity, and if it ran: our technicians ask because those replies set both work and price. You hear that price by phone, before anybody sets off. Your system is then purged thoroughly, once that tank is emptied. AdBlue crystallises and is corrosive to some of the metals in a fuel system, so it does not wash out on its own — which is why that counts more here than with petrol. The filter cleaned or, if it must be, replaced; fresh diesel in; then a check of the vehicle. Before we leave, we fire it up and confirm that it is running properly. If your motor hasn't 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 after dark. Payment is on the day, not upfront, and you are given the paperwork your insurer asks for: an engineer report and a VAT invoice. Before we get there, have a look at your policy; plenty carry cover for misfuelling. ## About Mynydd-bach Mynydd-bach is a suburban area located inland, approximately 2.9 miles from Swansea city centre, and sits at an elevation of around 148 metres. Mynydd-bach is characterized by its semi-detached housing stock, which is typical of many suburban areas in south Wales. Mynydd-bach is close to nearby places such as Tirdeunaw, Mynydd-Garn-Lwyd, and Clase, and is home to a population of around 3613 people. ## Mynydd-bach and Swansea: AdBlue drains across the area As a residential suburb, Mynydd-bach has the same vans as nearby areas — Mynydd-Garn-Lwyd, Clase — all the way across SA postcodes and the surrounding area around them. Fastest of all: give a SA5 7 postcode to our van. No need to move the car. The drain takes place on the spot, whether a drive, a road by Morris Castle, or a lay-by towards Knoyle Park. If you are near a border, or somewhere hard to describe like the back of The Salvation Army, ring and ask instead of guessing. ## For Mynydd-bach people, the short version Before you tip, read the cap. If AdBlue has gone in the diesel tank regardless, leave the vehicle off then call 0333 366 0103. Petrol in Diesel drains it where it sits, anywhere in Swansea.