--- title: Explained: AdBlue in a Diesel Tank Trostrey Common canonical: https://www.petrolinadieselcar.co.uk/adblue-in-diesel/trostrey-common-monmouthshire/ location: Trostrey Common county: Monmouthshire latitude: 51.732830 longitude: -2.894730 service: AdBlue in a Diesel Tank updated: 2026-10-06 --- # Why It Occurs and How to Prevent It: AdBlue in a Diesel Tank in Trostrey Common Keep your engine and ignition off and call 0333 366 0103 first — reading can wait when AdBlue is already in the diesel tank. Caught before the motor runs, it's generally a drain and a thorough flush, done where the car is in Trostrey Common. The remainder of this page covers why it takes place and how to make sure it doesn't — useful if you're reading ahead of time. ## AdBlue in a diesel car: two tanks, two fillers Not one liquid but two: that is how plenty of modern diesels around Trostrey Common and Llancayo run, with diesel feeding your engine. The exhaust, not your motor, is where AdBlue goes: dosed into the fumes to clean them, from its own tank. Different tanks, different fillers. On a lot of vehicles the two sit side by side under the same flap; on others the AdBlue filler is in your boot or under the bonnet. Filling your diesel side at the pump goes on constantly. Seldom topped up, AdBlue usually comes out of a bottle, tipped by a driver who has to stop and think what filler it needs. That gap is where the mistake lives. ## AdBlue in your diesel tank in Trostrey Common: how it happens Carelessness rarely causes it. Instead is three things coming up together. To start with, the warning. Low AdBlue triggers a message from your car, and running dry leads to limp mode — hence a rushed top-up, perhaps before work off Wainfield Lane, perhaps outside The Hall Inn on the way home after work. Then, the hand goes for the cap it knew on the old vehicle — since a hire car, a new motor or a company car places the fillers where your last one didn't. A spout-topped bottle finds no resistance at a diesel filler no more than at an AdBlue one. And so the pour, after started, keeps on. The same few seconds settle it, in the middle of Trostrey Common or out in Gwehelog. ## Telling the AdBlue filler from the diesel filler Before you pour anything, whether on a drive in Rhadyr or a forecourt around Trostrey Common, check these. They take a few seconds. - Colour and marking: an AdBlue cap is commonly blue, or says "AdBlue", where a diesel cap usually doesn't. Go by the cap, not its position. - Look at the size: the smaller filler neck is, on many cars, the AdBlue one. - The flap. Look inside your fuel flap for a label. Plenty of motors say there which fuel goes where. - Cannot see it next to your diesel inlet? In that case look beneath the bonnet or inside the boot — the handbook will say which. - Check with the person who drove it last — before you leave, not when the light comes on — if you pick up a hire or company car from somewhere like the car park outside Pontypool and New Inn. ## How to top up without AdBlue in your diesel tank For the day the light comes on — wherever you are across Monmouthshire — a routine to use. - Park then switch off. Not on a slope, not with the motor running, and not in a rush on the side of Monmouth Road. - Find the AdBlue filler and read the cap. Say "AdBlue" out loud as you unscrew it. It sounds silly and it does the trick. - Both under a single flap? So make sure the lid on the diesel side is still shut before raising the bottle. - Gently does it, through the bottle's own spout, till it is full or the bottle is empty. - Close the cap and check again. Make sure the diesel cap was never opened. Only then start the vehicle. Spot at stage two or three that it's already gone into your diesel side? So stop right there. Leave out step five entirely. ## AdBlue in your diesel tank already, around Trostrey Common? Brief order, then. First: your engine remains off. On plenty of diesels your ignition alone runs the fuel pump, so don't switch the vehicle on. Don't top up with diesel to dilute it: AdBlue doesn't mix with diesel, it sinks to the bottom of that tank, where the fuel is pulled from. On a forecourt — BP, Gulf or another — the staff will normally help roll your car away, if you ask. Leave it where it is if you are on your own driveway in Trostrey Common. When the motor has run by now, stop somewhere safe and switch the vehicle off. Come off the M4 — under 10 miles out of Trostrey Common — at the first exit. Tell us about how far it went: a run towards Newport, under 15 miles away, is a bigger job than a short hop across Trostrey Common. ## What takes place when we get there in Trostrey Common The van reaches your car wherever it stopped — your own drive, beside Gwehelog Methodist Church, or outside the local primary school. The replies decide this work and the price, so our engineers ask what went in, roughly how much, and if it's run. No one heads out until you have heard the price over the phone. Then your tank is cleared and the fuel system purged thoroughly. More than with petrol, it matters with AdBlue: crystals form, some metals are attacked, and nothing clears out on its own, no matter how long it is left. Filter cleaned or, where it must be, swapped; clean diesel in; and then a check of the car. Your engine is fired up next and tested to be sure it runs correctly, all before our engineers leave. Using pumps safe on a working forecourt and quiet enough to use outside a house at night, most jobs in which your engine hasn't run take about half an hour once our engineers are there. You pay on the day, with nothing upfront, and get a VAT invoice and an engineer report for your insurer. It's worth checking your insurance as the van travels to you: misfuelling cover is included with many policies. ## About Trostrey Common, briefly Trostrey Common is a small locality in Monmouthshire, situated inland at an elevation of 73 metres, approximately 10.9 miles from Newport. Trostrey Common is characterised by its detached housing and rural setting, with nearby places including Gwehelog and Gwehelog Common. Trostrey Common has a population of around 502 people, and is located near the Llandenny Walks. Trostrey Common is also relatively close to major cities, with London being 119.7 miles away. ## AdBlue drains across Monmouthshire, Trostrey Common included Gwehelog Common and Llandenny Walks are among the towns near Trostrey Common, a small village, that the same vans cover, over NP postcodes. The van gets to you fastest with a postcode starting NP15 1. The car doesn't need to shift. We drain it where it is — a side street close to Gwehelog Village Hall, a lay-by on the way to Camp Wood, a driveway. If you are close to a border, or somewhere hard to explain like the back of St. Davids, ring and ask instead of guessing. ## The short version for Trostrey Common motorists Pour no AdBlue till you have read the cap. Still AdBlue in the diesel tank? Petrol in Diesel will empty it where it is, wherever around Monmouthshire: keep the vehicle off then phone 0333 366 0103.