--- title: Newtown: AdBlue in a Diesel Tank, Explained canonical: https://www.petrolinadieselcar.co.uk/adblue-in-diesel/newtown-rhondda-cynon-taf/ location: Newtown county: Rhondda Cynon Taf latitude: 51.679910 longitude: -3.371290 service: AdBlue in a Diesel Tank updated: 2026-10-12 --- # AdBlue in a Diesel Tank in Newtown: How It Happens and How to Prevent It Pause reading a minute when the diesel tank already holds AdBlue in it: ignition off, engine off, then ring 0333 366 0103. In Newtown, finding it before the engine turns usually leaves a drain and a full flush on the spot. Nothing happened yet? Further down, the rest of the page explains the reasons it occurs and the ways to prevent it altogether. ## Why does AdBlue in a diesel car need its own filler? No single liquid but two: that's what many modern diesels near Newtown and Caegarw carry, with diesel for your engine. AdBlue goes to the exhaust, where it is sprayed into the gas to fresh it, and it lives in a tank of its own. 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. Topping up the diesel side at the pump goes on all the time. The AdBlue side is fuelled far less regularly, usually from a bottle, and usually by somebody who has to stop and think where it goes. It's in the gap that the slip happens. ## AdBlue in the diesel tank in Newtown: how it occurs Carelessness seldom causes it. Instead is three things coming up together. The warning comes first. As AdBlue runs low your car tells you, and if it runs out altogether, the vehicle drops into limp mode. So the top-up is done in a hurry: on a drive off Upper Forest Level before work, or in the car park outside The Baileys Arms on the way home. The old car's cap is where your hand goes — yet a rental car, a new vehicle or a company car keeps the fillers somewhere else. That's the second thing: an unfamiliar car. Third, the spout fits: diesel filler or AdBlue one, it goes in just as easily, and once the pour begins, nothing halts it. It takes a few seconds, be it out in Miskin or right in the centre of Newtown. ## How to tell the AdBlue filler from the diesel one Look at these before pouring, at a forecourt around Newtown or a driveway over in Perthcelyn. A few seconds, that's all. - Where it sits misleads; the cap does not. AdBlue caps are often blue or carry the name "AdBlue" — diesel ones normally do not. - On plenty of motors, the size gives it away: AdBlue gets the smaller filler neck. - A label inside the fuel flap often says which fuel goes where, on many cars. Look for it. - Can't find it next to your diesel filler? Then look beneath the bonnet or in the boot — the owner's manual says where. - Ask the person who drove it last — before you leave, not when the light comes on — when you pick up a hire or company car from somewhere like the car park outside Mountain Ash. ## Keeping AdBlue out of your diesel tank when you top up When the light goes on, anywhere across Rhondda Cynon Taf, use this routine. - Stop on level, motor off, with time in hand — not rushing on the side of Lower Forest Level. - Find the AdBlue filler, check the cap, and say the word "AdBlue" out loud while unscrewing it. It seems silly. It does the trick. - If both sit under one flap, check your diesel cap is still closed before you lift the bottle — then leave the vehicle on. - Gently is best, through the bottle's own spout, until it's full or the bottle is empty. - Before starting your car, close the cap and check again that your diesel cap was never opened off. If at step two or three you find you have already poured into your diesel side, stop there. Never carry on to stage five. ## Put AdBlue in your diesel tank around Newtown already? Don't start your engine: that is how the short order of things starts. Do not switch the ignition on; on plenty of diesels that alone runs the fuel pump. Filling up with diesel won't thin it: rather than mixing, AdBlue sinks to the bottom of your tank, just where fuel is taken from. If you're on a forecourt, whether it is the Esso or the Texaco, ask the attendants to help push the vehicle clear of the petrol pump. Leave it where it is if you are on your own drive around Newtown. Where your motor has run by now, stop safely and turn the car off. Newtown sits under 15 miles from the M4; there, use the next junction. Tell us about how far it went: a run towards Cardiff, under 25 miles away, is a bigger job than a short hop across Newtown. ## Our arrival around Newtown, and what takes place next Our van reaches the vehicle wherever it stopped — your own drive, beside Canolfan Pennar Community Hub, or by the local primary school. Both the work and the price rest on three replies — what fluid, what quantity, and whether it has run — so we ask. You get that price by phone, before anyone heads out. Then that tank is cleared and your system flushed thoroughly. AdBlue crystallises and is corrosive to some of the metals in a fuel system, so it doesn't wash out on its own — which is why that counts more with AdBlue than with petrol. Once the fuel filter is cleaned — or replaced, where needed — clean diesel is added, and then your car gets tested. Before leaving, we fire it up and check that it is running correctly. Unrun vehicles mostly need a half-hour visit from the moment we arrive. The kit is safe on a live forecourt, 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. Plenty of insurance policies include misfuelling cover, and so it is worth checking yours while we are on the way. ## About Newtown and where it is Newtown is a suburban area in Rhondda Cynon Taf, situated on the riverside at an elevation of 119 metres. Newtown lies near the communities of Miskin and Darranlas, and is close to Mountain Ash. Newtown has a population of around 4286 people, predominantly living in terraced housing. ## Newtown and Rhondda Cynon Taf: AdBlue drains across the area Being a new town, Newtown shares its vans nearby places — Darranlas, Mountain Ash — right through CF postcodes and the wider area around them. A postcode starting CF45 4 gets our van to you fastest. There's no need to move the vehicle. A driveway, a lay-by on the way to Gwynifor Park, a side street close to Mountain Ash Library: our technicians drain the car where it is. Guessing doesn't help behind Guto Nyth Bran, close to a boundary, or anywhere hard to pin down; phone and check. ## The short version for Newtown people Pour nothing until you have read the cap. If AdBlue has gone in your diesel tank anyway, leave it off and ring 0333 366 0103. Petrol in Diesel clears it where it sits, anywhere in Rhondda Cynon Taf.