--- title: AdBlue in a Diesel Tank Glenboi: Explained canonical: https://www.petrolinadieselcar.co.uk/adblue-in-diesel/glenboi-rhondda-cynon-taf/ location: Glenboi county: Rhondda Cynon Taf latitude: 51.686340 longitude: -3.396850 service: AdBlue in a Diesel Tank updated: 2026-10-09 --- # Why It Occurs and How to Prevent It: AdBlue in a Diesel Tank in Glenboi AdBlue already in the diesel tank? In that case set this page aside for now, leave your ignition and motor off, then ring 0333 366 0103. Caught before your motor runs, it's generally a drain and a thorough flush, done where the vehicle is in Glenboi. Not happened yet? Further down, the rest of the page covers the why it takes place and the ways to avoid it for good. ## Why does AdBlue in a diesel car need its own filler? Not one liquid but two: that's how many newer diesels around Glenboi and Darranlas run, with diesel for the engine. Stored in a tank of its own, AdBlue is fed into the exhaust stream to clean it. There's a filler on each tank. On a lot of cars the two sit side by side under the same flap; on others the AdBlue filler is in your boot or under the bonnet. The diesel side is fuelled at the petrol pump all the time. The AdBlue side is topped up far less frequently, normally from a bottle, and normally by a person who has to stop and think where it goes. It is in that gap that the error lives. ## How does AdBlue in the diesel tank occur around Glenboi? Seldom is it carelessness: normally three things coincide. To start with, the warning. Low AdBlue triggers a message from the vehicle, and letting it run out means limp mode — hence a rushed top-up, perhaps before work off Fernhill, or at Mountain Ash Inn on the way home that evening. The old car's filler is where your hand goes — yet a rental car, a new vehicle or a company car puts the fillers elsewhere. That's the second thing: a strange car. Third, the bottle goes in: a diesel filler or AdBlue filler, it goes in just as easily, and once the pour starts, nothing stops it. Whether it takes place in Cwmpennar or the middle of Glenboi, it's the same few seconds. ## The AdBlue filler and the diesel filler: telling them apart Whether a Glenboi forecourt or a driveway out in Mountain Ash, take a couple of seconds over these before any is poured in. - Check the cap instead of going by where it sits: AdBlue caps are regularly blue or marked "AdBlue", and diesel ones normally are not. - The size. On many motors the AdBlue filler neck is the smaller of the two. - Lift the flap and check for a label — plenty of motors show what belongs in which filler right there. - Can't find it beside your diesel inlet? In that case look beneath the bonnet or in your boot — the owner's manual says where. - The person who drove the car last. On a hire or company car collected from somewhere like the car park outside Fernhill, ask before you leave, not when the light comes on. ## AdBlue top-ups that never reach the diesel tank Wherever around Rhondda Cynon Taf the light comes on, this is a routine for the day. - Turn off once parked — level ground, engine off, and not in a rush beside Glenboi on the verge. - Say "AdBlue" out loud as you unscrew the cap, once you find the AdBlue filler and reading it. Daft, perhaps, 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 it on. - Finish once your tank fills or the bottle runs dry; until then, pour slowly through the own spout. - Only then, start your car: close the cap, check a second time, and make sure your diesel cap was never opened. Discover during the second or third stage that AdBlue went into the wrong tank? That's where you stop. Skip step five altogether. ## Put AdBlue in the diesel tank in Glenboi already? Then the order of things is short. Don't start the motor. Leave the ignition off as well, because on many diesels switching it on alone starts the fuel pump. Filling up with diesel won't thin it: instead, AdBlue sinks to the bottom of your tank, right where the fuel is taken from. If you're on a forecourt, whether it's the BP or the Esso, ask the staff to help roll your car clear of the petrol pump. If you're on your own driveway in Glenboi, leave it where it is. If your engine has already run, stop as soon as it is safe and switch off. The next exit is the place to leave when you're on the M4, under 15 miles from Glenboi. Tell us about how far it went: a run towards Cardiff, under 25 miles away, is a bigger job than a short hop across Glenboi. ## Our arrival in Glenboi, and what takes place next Wherever the vehicle came to rest, whether by the local primary school, beside Community Link Building or at home, our van travels to it. Which fluid got in, the amount, and whether it ran: we ask since those replies decide the work and price. No one heads out until you have had the price by phone. After that: a drain, then a full flush of the whole system. Not like petrol, AdBlue forms crystals and eats at certain fuel-system metals, and neither washes out unaided. That is why it counts more. The filter flushed or, where needed, swapped; fresh diesel in; and then a test of your car. We don't leave until it has been fired up and is running smoothly. Most jobs are finished in roughly half an hour after we arrive, as long as the motor hasn't run — and the pumps we use are safe on a live forecourt and quiet after dark outside a house. Payment happens on the day, not upfront, and you are given the documents your insurer asks for: an engineer's report and a VAT invoice. Many insurance policies include misfuelling cover, so it's worth checking yours while we are on the way. ## About Glenboi itself Glenboi is a small suburban area situated on the riverside in Rhondda Cynon Taf, with a mix of terraced housing and local amenities. Glenboi sits at an elevation of 114 metres, near the communities of Cwmpennar, Abercwmboi, and Cefnpennar. Glenboi is located approximately 17 miles north of Cardiff, and its residents have access to the city's services and facilities. Glenboi has a population of around 1280 people, living in a relatively small and close-knit community. ## Glenboi and Rhondda Cynon Taf: AdBlue drains across the area Abercwmboi and Cefnpennar are among the towns around Glenboi, a residential suburb, that the same vans cover, throughout CF postcodes. Give a postcode beginning CF45 3, and our van gets there fastest. There's no need to move your car. Draining happens right there, be it a driveway, a road near Darran Las Community Building, or a lay-by on the way to Caedrawnant Recreation Ground. Guessing won't help behind Life in the Nation Church, close to a border, or somewhere hard to pin down; phone and check. ## In short, for Glenboi people Before you pour, read the cap. Petrol in Diesel empties it on the spot, anywhere around Rhondda Cynon Taf, if AdBlue has gone in the diesel tank regardless — so leave the car off and ring 0333 366 0103.