--- title: Glascoed: AdBlue in a Diesel Tank, Explained canonical: https://www.petrolinadieselcar.co.uk/adblue-in-diesel/glascoed-monmouthshire/ location: Glascoed county: Monmouthshire latitude: 51.709840 longitude: -2.967830 service: AdBlue in a Diesel Tank updated: 2026-10-06 --- # AdBlue in a Diesel Tank in Glascoed: Why It Happens and How to Prevent It Stop here a minute when your diesel tank already holds AdBlue in it: ignition off, engine off, and call 0333 366 0103. Normally, when your engine hasn't turned, it's emptied and thoroughly flushed where your car sits in Glascoed. Reading before the event? In that case the rest explains how it happens and what to prevent it ever happening. ## AdBlue in a diesel car: two tanks, two fillers No single liquid but two: that's what plenty of newer diesels near Glascoed and Pentre-waun carry, with diesel for the motor. Your exhaust, not the engine, is where AdBlue goes: dosed into the gas to fresh them, from a separate tank. There is a filler on each tank. Under one flap, next to each other: that's the layout on many motors. On others, AdBlue's filler sits beneath the bonnet or in your boot instead. Diesel goes in on every forecourt call-out, again and again. Seldom filled, AdBlue normally comes from a bottle, tipped by someone who has to stop and think which filler to use. That gap is where the slip lives. ## Glascoed: how AdBlue in your diesel tank occurs Three things tend to line up, and carelessness is seldom one of them. To start with, the warning. Low AdBlue brings a message from your car, and running dry means limp mode — hence a rushed top-up, maybe before work off Wern Lane, perhaps outside Halfway House on the way home after work. Next, your hand goes for the cap it would have used on the old motor — since a rental car, a new motor or a company car puts the fillers where your last one did not. A spout-topped bottle finds no obstacle at a diesel filler any more than at an AdBlue one. And so the tip, after begun, carries on. Monkswood or the heart of Glascoed: it is the same few seconds in both. ## Telling the AdBlue filler from your diesel filler Before you tip anything, whether on a driveway in Llanvihangel Pontymoel or a forecourt in Glascoed, check these. They take a couple of seconds. - Colour and marking: an AdBlue cap is often blue, or says "AdBlue", where a diesel cap usually does not. Go by the cap, not where it sits. - Check the size: the smaller neck is, on plenty of motors, the AdBlue one. - Look inside the fuel flap: many vehicles have a label there showing which fuel goes where. - Cannot find it next to your diesel filler? In that case check below the bonnet or in the boot — the handbook says where. - Picking up a hire or company car, say at the car park outside Pontypool and New Inn? Check with the person who drove the vehicle last before leaving, not once the light goes on. ## AdBlue top-ups that never reach the diesel tank The day the light goes on, anywhere across Monmouthshire, follow this routine. - Park and switch off. Not on a slope, not with the motor running, and not in a rush on the side of Twyn Lane. - Say "AdBlue" out loud as you unscrew the cap, after you find the AdBlue filler and reading it. Silly, yes, yet it works. - Leave your diesel cap on. If both sit under one flap, check the diesel cap is still closed before you lift the bottle. - Tip slowly, using the bottle's own spout. Stop when it is full or when the bottle is empty. - Only then, start your car: close the cap, check a second time, and make sure the diesel cap was never opened. If at step two or three you find you have already poured into the diesel side, stop there. Do not go on to step five. ## AdBlue in the diesel tank already, around Glascoed? Then the order of things is short. Do not start the engine. Don't switch your ignition on; on plenty of diesels that alone runs the fuel pump. Thinning it with extra diesel won't work, since AdBlue sinks to the bottom instead of mixing — and that is where your fuel is drawn from. If you're on a forecourt, whether it is the Shell or the BP, ask the attendants to help roll the car away from the pump. If you're on your own drive around Glascoed, leave the vehicle where it is. Stop as soon as it is safe then switch off, if your motor has already run. The next junction means the place to come off if you're on the M4, under 10 miles from Glascoed. Distance counts — a quick hop across Glascoed is a smaller job than driving under 10 miles to Newport — so say about how far it went. ## Our arrival around Glascoed, and what happens next Anywhere your car came to rest, be it outside the local primary school, near St Michaels or at home, the van comes to it. Both the work and the quote depend on three replies — what liquid, which amount, and if it's run — so we ask. During the phone call itself, you are told the price — ahead of dispatch. Emptying that tank comes next, followed by a full flush of the fuel system. More than with petrol, it matters with AdBlue: the crystals form, some metals corrode, and none of it clears away unaided, no matter how long it is left. Testing comes at the end: before that, fresh diesel goes in, and the fuel filter is cleaned or replaced as needed. The motor is started next and checked to be sure it runs properly, all before we head off. Most jobs are finished in roughly half an hour after our engineers get there, as long as your engine has not run — and the pumps our engineers use are safe on a live forecourt yet quiet after dark beside a house. Your insurer usually wants the engineer's report and your VAT invoice, and both are yours once this job is done. Payment is on the day, with no money upfront. Plenty of insurance policies include misfuelling cover, so it's worth checking yours while we're on the way. ## About Glascoed, briefly Glascoed is a small village in Monmouthshire, situated on the banks of a river at an elevation of 82 metres. Glascoed lies near the cities of Newport and Cardiff, and is close to the villages of Monkswood and Little Mill. Glascoed has a population of around 527 people, predominantly living in detached houses. Glascoed is located approximately 122.7 miles from London, making it a relatively rural community. ## AdBlue drains round Glascoed, and Monmouthshire beyond Little Mill and Penpedairheol are among the places around Glascoed, a village, that the same vans cover, throughout NP postcodes. Quickest of all: give a NP4 0 postcode to the van. There's no need to shift the vehicle. A driveway, a lay-by on the way to Lower Common, a side street near Little Mill Baptist Chapel: our engineers drain the vehicle where it stands. Tricky to pin down, like the back of Little Mill Village Hall? Close to a border? Asking is better than guessing, so ring. ## Glascoed people: the short version Tip no AdBlue until you've read the cap. If AdBlue has gone in your diesel tank all the same, leave the car off then phone 0333 366 0103. Petrol in Diesel empties it where it stands, anywhere across Monmouthshire.