--- title: Downend: AdBlue in a Diesel Tank, Explained canonical: https://www.petrolinadieselcar.co.uk/adblue-in-diesel/downend-hampshire/ location: Downend county: Hampshire latitude: 50.851210 longitude: -1.156380 service: AdBlue in a Diesel Tank updated: 2026-10-18 --- # AdBlue in a Diesel Tank in Downend: How It Happens and How to Avoid It If AdBlue is already in your diesel tank, stop reading for a moment: leave the engine and your ignition off then phone 0333 366 0103. A drain plus a full flush, carried out just where your car stands in Downend, is normally what it takes when caught before the motor runs. If you are reading before it has happened, the remainder of this page is about why it happens and how to make sure it doesn't. ## Two fillers, two tanks: AdBlue in a diesel vehicle Many newer diesels on the roads about Downend and Fleetlands carry two liquids, not one. Diesel goes to the motor. AdBlue's own tank holds it, and from there it is sent to your exhaust, and there a spray cleans the gas. Separate tanks, separate fillers. Under one flap, next to each other: that is the layout on a lot of motors. On others, AdBlue's filler is beneath the bonnet or in your boot instead. The diesel side is topped up at the petrol pump all the time. The AdBlue side is topped up far less regularly, usually from a bottle, and usually by someone who has to stop and think where it goes. Mistakes happen in the gap between them. ## How does AdBlue in your diesel tank occur around Downend? Carelessness rarely causes it. What does 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 car goes into limp mode. So the top-up is done in a hurry: on a driveway off Down End Road before work, or in the car park outside The Delme Arms on the way home. Next, the hand reaches for the cap it would have used on the old vehicle — because a rental car, a new car or a company car places the fillers somewhere your last one didn't. A spout-topped bottle finds no resistance at a diesel filler any more than at an AdBlue one. And so the tip, after begun, carries on. It's a few seconds, be it out in Wallington or bang in the heart of Downend. ## How to tell the AdBlue filler from the diesel one Before you pour anything, whether on a drive in Portchester or a forecourt in Downend, check these. They take a couple of seconds. - The cap. The AdBlue cap is often blue, or marked "AdBlue". The diesel cap normally isn't. Read it rather than going by where it sits. - The size. On many motors the AdBlue filler neck is the smaller of the two. - Lift the flap and look for a label — plenty of vehicles show which goes in which inlet just there. - The handbook shows where it is when your filler isn't next to the diesel cap: your boot, or under the bonnet. - The previous driver will know. Ask as you pick up a rental or fleet car — from Portchester's car park, say — not when the warning comes on. ## How to top up without AdBlue in your diesel tank A routine for the day the light comes on, wherever across Hampshire that is. - Not in a rush on the side of Portchester Road, not on a slope, not with your motor running: park then switch off properly. - Say "AdBlue" out loud as you unscrew the cap, after you find the AdBlue filler and read it. Silly, perhaps, but it does the trick. - If both sit under one flap, check the diesel cap is still closed before you lift the bottle — then leave it on. - Slowly does it, through the bottle's own spout, till it is full or the bottle is empty. - Only then, start your car: close the cap, check again, and make sure the diesel cap was never opened. Discover at the second or third stage that the bottle went in the wrong tank? That is where you stop. Don't go on to step five. ## Put AdBlue in the diesel tank around Downend already? Brief order, then. Top of that: the engine remains unstarted. Leave the ignition off too, since on many diesels switching it on by itself starts your fuel pump. AdBlue doesn't mix with diesel — it sinks to the bottom of the tank, where your fuel is drawn from — so don't top up with diesel to thin it. At a forecourt — BP, Sainsbury's or another — the attendants will usually help roll your car away, if you ask. Your own driveway around Downend is where it stays. Where the motor has run already, pull over somewhere safe and switch the car off. On the M27, under a mile from Downend, that means the next exit. Mileage matters — a short hop across Downend makes a smaller job than driving under 5 miles to Portsmouth — so say roughly how far it went. ## When our technicians turn up around Downend, what takes place? Outside Wicor Primary School, near 247 Fitness or on your own driveway: wherever the car has stopped, our technicians come to it. Both the work and our price depend on three answers — what fluid, what amount, and whether it's run — so our engineers ask. That quote is given on the call, ahead of any van leaving. Then that tank is drained and the fuel system cleaned thoroughly. 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 counts more here than with petrol. Once your filter has been flushed — or replaced, where needed — clean diesel is added, and finally the vehicle gets tested. Before leaving, our engineers start the car and check that it is running correctly. Most jobs are done in roughly half an hour once our engineers arrive, as long as the engine hasn't run — and the pumps we use are fine on a live forecourt and quiet after dark beside a house. Your insurer usually wants the engineer's report and the VAT invoice, and you get both at the end. Payment is on the day, with no money upfront. It is worth looking at your insurance as the van travels to you: misfuelling cover is included with many policies. ## About Downend and where it is Downend is a coastal suburban area in Hampshire, situated near the major city of Portsmouth. Downend sits at a low elevation of around 13 metres, close to the Solent Strait and the Isle of Wight. Downend is characterized by its predominantly detached housing stock, reflecting its development as a residential area. Downend is located near other suburban areas, including Wallington and Fareham. ## Downend and Hampshire: AdBlue drains across the area Being a residential suburb, Downend shares its vans surrounding areas — Fareham, North Fareham — right through PO postcodes and the surrounding area around them. Quickest of all: quote a PO16 8 postcode to our van. Moving the vehicle is not necessary. Draining happens on the spot, be it a drive, a street near Wicor Recreation Ground, or a layby towards Wicor Recreation Ground. Ring and ask instead of guessing if you're near a boundary, or somewhere hard to explain, like the back of Fort Wallington. ## In short, for Downend drivers Read the cap before you tip. AdBlue in your diesel tank regardless? Keep the vehicle off and call 0333 366 0103; Petrol in Diesel empties it where it stands, throughout Hampshire.