--- title: AdBlue in a Diesel Tank Derry? Read This canonical: https://www.petrolinadieselcar.co.uk/adblue-in-diesel/derry-county-londonderry-bt47-6/ location: Derry county: County Londonderry latitude: 54.995800 longitude: -7.307400 service: AdBlue in a Diesel Tank updated: 2026-10-14 --- # How It Occurs and How to Avoid It: AdBlue in a Diesel Tank in Derry If AdBlue is already in your diesel tank, stop reading for a moment: leave your engine and your ignition off then phone 0333 366 0103. A drain and a thorough flush, done right where your vehicle sits around Derry, is usually what it needs when caught before your motor runs. Nothing happened yet? Below, the page covers the reasons it happens and the how to avoid it altogether. ## Why does AdBlue in a diesel motor need its own filler? No single liquid but two: that is what many newer diesels around Derry and Maydown carry, with diesel feeding your engine. Your exhaust, not the motor, is where AdBlue ends up: sprayed into the gas to clean it, from a separate tank. Separate tanks, separate fillers. Plenty of vehicles have a single flap for the two, while some put the AdBlue filler to your boot or under the bonnet. At the petrol pump, your diesel side is topped up all the time. Rarely topped up, AdBlue normally comes out of a bottle, poured by a driver who has to stop and think what cap to use. It is in the gap that the error lives. ## How does AdBlue in your diesel tank occur around Derry? It's rarely carelessness. Three things tend to line up. To start with, the warning. Low AdBlue brings a message from the vehicle, and letting it run dry leads to limp mode — hence a rushed top-up, maybe before work off Crown Street, or at the pub in the village on the way home after work. Then, the hand reaches for the cap it would have used on the old vehicle — since a rental car, a new car or a company car puts the fillers somewhere your last one did not. No part stops the tip once it has started, because a bottle with a spout goes into a diesel filler as easily as an AdBlue one. The bottle fits. Nixons Corner or the middle of Derry: it takes the same few seconds either way. ## The AdBlue filler and your diesel filler: telling them apart Before you pour anything, whether on a drive in Newbuildings or a forecourt around Derry, check these. They take a few seconds. - The cap. The AdBlue cap is frequently blue, or marked "AdBlue". The diesel cap usually is not. Read it instead of going by where it sits. - Plenty of cars give AdBlue the smaller neck of the two. - Look inside your fuel flap: many motors carry a label there saying which fuel goes where. - The handbook. If the filler isn't by the diesel cap, it is in your boot or under the bonnet, and the handbook says which. - Check with the person who drove it last — before you leave, not when the light comes on — when you collect a hire or company car from somewhere like the car park outside the nearest station. ## How to top up without AdBlue in the diesel tank A routine for the day the light comes on, wherever in County Londonderry that is. - Turn off once parked — level ground, engine off, and never in a rush by Crom Street at the roadside. - Say "AdBlue" out loud as you unscrew the cap, after finding the AdBlue filler and read it. Daft, yes, yet it works. - If both sit under one flap, check the diesel cap is still closed before you lift the bottle — and leave the vehicle on. - Using the bottle's own spout, tip slowly — and stop when it is full or the bottle is empty. - Before starting your car, close the cap and check a second time that your diesel cap was never opened off. Find at the second or third step that the bottle went into the wrong tank? That is where you stop. Don't go on to step five. ## Derry: already put AdBlue in the diesel tank? Brief order, then. First: your motor stays unstarted. The fuel pump starts on many diesels as soon as the ignition goes on — and so keep it off. Topping up with diesel will not dilute it: instead, AdBlue drops to the bottom of the tank, right where the fuel is drawn from. On a forecourt — the nearest petrol station, another forecourt nearby or another — the staff will usually help roll your car away, if you ask. On your own drive around Derry? So your car stays put. Already run? Pull over when it is sensible, then turn off. Leave the M77 — over 50 miles out of Derry — at the next junction. About how far did it go? Crossing Derry is less work than a run of over 50 miles towards Armagh, and so say. ## What occurs when our engineers arrive around Derry Our van reaches your car anywhere it has come to rest — your own driveway, beside the centre, or outside the local primary school. Our technicians ask what went in, about how much, and if it's run, because the replies determine the work and the quote. The price is given over the phone, ahead of any van leaving. Next: draining, then a full flush of the whole system. AdBlue crystallises and is corrosive to some of the metals in a fuel system, and so it does not wash out on its own — which is why that matters more with AdBlue than with petrol. Your filter is cleaned, or replaced where it needs to be; clean diesel goes in; and your car is tested. The engine is fired up next and tested to be sure it runs smoothly, all before our technicians head off. If the motor hasn't run, most jobs take about half an hour once we are there, using pumps that are fine on a busy forecourt and quiet enough to use outside a house after dark. Payment is on the day, not upfront, and you are given the paperwork your insurer wants: an engineer report and a VAT invoice. Wrong-fuel cover is included in plenty of insurance policies — so make use of the wait to look at yours. ## About Derry, for a moment Derry is a city located in County Londonderry, Northern Ireland, situated inland near the River Foyle. Derry sits at an elevation of 31 metres, approximately 382 miles northwest of London. Derry is characterised by its predominantly terraced housing stock and is close to nearby places such as Nixons Corner, Ardmore, and Strathfoyle. Derry has a population of around 55,000 people and is a significant urban centre in the region. ## AdBlue drains in Derry and across County Londonderry Derry is a city, and our teams that cover it also work the towns near it, Ardmore and Strathfoyle among them, across the BT postcode area. Fastest of all: quote a BT47 6 postcode to our van. The car doesn't need to move. Wherever it stands — beside a street just off the centre, on a layby heading to the green space at the edge of the village, on a drive — that's where it is drained. Ring and ask instead of guessing if you're near a boundary, or somewhere hard to describe, like the back of the far end of the built-up part. ## In short, for Derry people Always, the cap; after that, the tip. Petrol in Diesel drains it on the spot, anywhere around County Londonderry, if AdBlue has gone in your diesel tank anyway — so leave it off then call 0333 366 0103.