--- title: Tynewydd: AdBlue in a Diesel Tank, Explained canonical: https://www.petrolinadieselcar.co.uk/adblue-in-diesel/tynewydd-rhondda-cynon-taf/ location: Tynewydd county: Rhondda Cynon Taf latitude: 51.678970 longitude: -3.546240 service: AdBlue in a Diesel Tank updated: 2026-10-15 --- # Tynewydd: How Does AdBlue End Up in a Diesel Tank, and How Do You Prevent It? AdBlue already in the diesel tank? In that case put this page aside for now, leave the ignition and motor off, then phone 0333 366 0103. Caught before your motor runs, it's normally a drain and a thorough flush, done where your car is around Tynewydd. Nothing happened yet? Further down, the page covers the why it occurs and the how to avoid it altogether. ## Two fillers, two tanks: AdBlue in a diesel car Plenty of newer diesels around Pen-yr-englyn, as well as Tynewydd, run on two fluids; your engine gets only the diesel. AdBlue's own tank keeps it, and from there it is sent to the exhaust, where a spray treats the fumes. Each tank has its own filler. On a lot of vehicles the two sit side by side under the same flap; on others the AdBlue filler is in the boot or under the bonnet. Filling the diesel side at the petrol pump happens constantly. The AdBlue side is fuelled far less commonly, usually from a bottle, and usually by someone who has to stop and think where it goes. It is in the gap that the error happens. ## How does AdBlue in the diesel tank happen around Tynewydd? Seldom is it carelessness: normally three things line up. Haste comes from the warning. The vehicle warns you as AdBlue runs low, and an empty tank puts it into limp mode — so the top-up gets done in a rush, before work on a drive off Eileen Place, or heading home in the car park at the pub in the village. Then the vehicle is unfamiliar. A hire car, a new car or a company car puts the fillers where your last one didn't, and the hand gets to for the cap it would have used on the old one. A spouted bottle finds no obstacle at a diesel filler no more than at an AdBlue one. So the tip, once begun, keeps on. It takes a few seconds, be it out in Treherbert or right in the centre of Tynewydd. ## Which filler is for AdBlue, and which for diesel? Check these before pouring, at a forecourt around Tynewydd or a drive over in Ynyswen. A few seconds, that's all. - Where it sits misleads; the cap doesn't. AdBlue caps tend to be blue or carry the name "AdBlue" — diesel ones usually do not. - Plenty of cars fit AdBlue the smaller filler of the two. - A label inside your fuel flap frequently shows which fuel goes where, on plenty of vehicles. Check for it. - The handbook says where it lives when your filler is not next to the diesel cap: the boot, or under the bonnet. - Collecting a hire or company car, perhaps at the car park at Treherbert? Ask the person who drove the vehicle last before leaving, rather than once the light comes on. ## Keeping AdBlue out of the diesel tank when you top up The day the light goes on, wherever across Rhondda Cynon Taf, follow this routine. - Not in a rush on the side of Alma Street, not on a slope, not with your engine running: park and switch off properly. - Daft as it sounds, saying "AdBlue" aloud as you unscrew the cap works — after you have located your filler and read the cap. - If both sit under one flap, check your diesel cap is still closed before you lift the bottle — and leave the vehicle on. - Stop when the tank is topped up or the bottle is empty; until then, tip gently through its built-in spout. - Shut the cap, then look once more — making sure your diesel cap remained closed throughout. Only then, start your car. Stop there if you find, at stage two or three, that you have already poured into the diesel side. Step five stays off limits. ## AdBlue in the diesel tank already, around Tynewydd? Then the order of things is short. Don't start the engine. The fuel pump starts on plenty of diesels as soon as the ignition is switched on — and so leave it off. Thinning it with more diesel fails, because AdBlue sinks to the bottom instead of blending — and that is where your fuel is sucked from. The staff at Texaco, Murco or any forecourt will normally lend a hand to push the vehicle clear when asked. At home around Tynewydd? So the vehicle remains where it is. When the motor has been run already, stop safely and switch the vehicle off. Tynewydd sits under 15 miles from the M4; on it, use the first junction. About how far did it go? Crossing Tynewydd is less work than a run of under 25 miles towards Swansea, and so say. ## Our arrival in Tynewydd, and what happens next Our van reaches your car anywhere it stopped — your own driveway, near Blaen-y-Cwm Baptist Chapel, or by the local primary school. Which fluid was put in, the amount, and whether it ran: our engineers ask since the replies set the work and quote. That quote is given on the call, ahead of any van leaving. Next: draining, then a full flush of the entire system. With AdBlue that matters more than with petrol: it crystallises and is corrosive to some of the metals in a fuel system, so it does not wash out on its own. The filter is flushed, or replaced where it needs to be; fresh diesel goes in; and the car is tested. Then our technicians fire it up and confirm it runs properly before we leave. Unrun vehicles mostly need a half-hour job after arrival. The kit is fine on a live filling station, and hushed enough for a residential street late at night. You pay on the day, with nothing upfront, and get a VAT invoice and an engineer report for your insurer. Before we get there, have a look at your insurance documents; plenty include cover for misfuelling. ## About Tynewydd, for a moment Tynewydd is a suburban area in Rhondda Cynon Taf, situated on the riverside at an elevation of 197 metres. Tynewydd is located near the communities of Treherbert, Blaencwm, and Blaenrhondda, and is approximately 17 miles from Swansea. Tynewydd has a population of around 2314 people, predominantly living in terraced housing. Tynewydd is part of the wider urban area in the south Wales valleys, with the capital city London being around 147 miles away. ## AdBlue drains round Tynewydd, and Rhondda Cynon Taf beyond As a residential suburb, Tynewydd shares its vans nearby areas — Blaencwm, Blaenrhondda — all the way through CF postcodes and the wider area around them. Quickest of all: give a CF42 5 postcode to our van. Your car doesn't need to move. Anywhere it stands — near Cenotaph, on a layby heading to Treherbert Park, at home — that is where it gets drained. If you are near a border, or somewhere hard to explain like the back of Blaencwm Community Centre, ring and ask rather than guessing. ## In short, for Tynewydd people Always, the cap; then, the pour. AdBlue in your diesel tank after all? Leave the car switched off then ring 0333 366 0103; Petrol in Diesel empties it on the spot, across Rhondda Cynon Taf.