--- title: AdBlue in a Diesel Tank Colthrop: Explained canonical: https://www.petrolinadieselcar.co.uk/adblue-in-diesel/colthrop-berkshire/ location: Colthrop county: Berkshire latitude: 51.399550 longitude: -1.237600 service: AdBlue in a Diesel Tank updated: 2026-10-12 --- # Why It Occurs and How to Avoid It: AdBlue in a Diesel Tank in Colthrop Pause reading for a moment when your diesel tank already has AdBlue in it: ignition off, motor off, and ring 0333 366 0103. Caught before your engine runs, it's normally a drain and a thorough flush, done where the car is around Colthrop. Nothing happened yet? Below, the rest of the page covers the reasons it occurs and the how to avoid it for good. ## AdBlue in a diesel motor: two tanks, two fillers Plenty of modern diesels around Midgham, as well as Colthrop, run on two liquids; your motor gets just your diesel. The exhaust, not your engine, is where AdBlue goes: sprayed into the fumes to clean them, from a separate tank. Separate tanks, different fillers. Under one flap, next to each other: that is the layout on many vehicles. On others, AdBlue's filler sits beneath the bonnet or in the boot instead. The diesel side is fuelled at the pump all the time. Someone who has to stop and think where it goes usually tops up the AdBlue side, from a bottle, and much less regularly. That gap is where the mistake lives. ## How AdBlue in the diesel tank occurs in Colthrop It is seldom carelessness. Three things tend to line up. First, the warning. Low AdBlue brings a warning from the vehicle, and letting it run dry leads to limp mode — so a hurried top-up, maybe before work off Enterprise Way, or at The Swan on the way home after work. The old car's filler is where the hand goes — yet a hire car, a new vehicle or a company car keeps the fillers elsewhere. That's a second thing: an unfamiliar car. A spouted bottle finds no resistance at a diesel filler any more than at an AdBlue one. And so the pour, once begun, keeps on. It takes a few seconds, whether in Thatcham or bang in the centre of Colthrop. ## How to tell the AdBlue filler from the diesel one Look at these first, at a forecourt in Colthrop or a drive out in Hopgoods Green. Seconds, that's all. - Colour and marking: an AdBlue cap is frequently blue, or says "AdBlue", where a diesel cap normally doesn't. Trust the cap, not its position. - Check the size: the smaller filler neck is, on plenty of motors, the AdBlue one. - The flap. Look inside the fuel flap for a label. Plenty of cars say there which fuel goes where. - The handbook. If the filler isn't by your diesel cap, it's in the boot or under the bonnet, and the handbook says which. - Collecting a hire or company car, say at the car park at Thatcham? Ask the person who drove the vehicle last before leaving, not once the light comes on. ## How to top up without AdBlue in your diesel tank The day the light comes on, wherever in Berkshire, follow this routine. - Park then switch off. Not on a slope, not with the engine running, and not in a rush on the side of Poffley Place. - Find the AdBlue filler, check the cap, and speak the word "AdBlue" aloud as you unscrew it. It sounds daft. It works. - Both behind a single flap? So make sure the lid on the diesel side is still shut ahead of lifting the bottle. - Using the bottle's own spout, pour slowly — and stop when it is full or the bottle is empty. - Close the cap and check a second time. Make sure the diesel cap was never opened. Only then start your car. Stop there if you find, at step two or three, that you have already poured into the diesel side. Skip step five entirely. ## Colthrop: already put AdBlue in your diesel tank? Brief order, then. First: the engine remains off. The fuel pump runs on many diesels the moment the ignition goes on — and so keep it off. Don't top up with diesel to thin it: AdBlue doesn't mix with diesel, it sinks to the bottom of your tank, where the fuel is pulled from. If you're on a forecourt, whether it is the Esso or the BP, ask the attendants to help roll your car clear of the petrol pump. Leave it where it is if you are on your own driveway around Colthrop. When your engine has been run by now, stop somewhere safe then switch the car off. On the M4, under 5 miles from Colthrop, that means the next junction. Roughly how far did it go? Crossing Colthrop is less a job than a run of under 25 miles to Winchester, so tell us. ## Colthrop: what occurs when we turn up Anywhere the vehicle has stopped, whether by Francis Baily Primary School, beside Thatcham Baptist Church or on your own drive, our van comes to it. Which liquid went in, the quantity, and whether it ran: our engineers ask since those answers decide the work and quote. Nobody heads out until you've had our quote by phone. Next: a drain, then a thorough flush of the whole system. More than with petrol, it matters here: crystals build up, some metals are attacked, and nothing clears away unaided, however long it is left. Your filter is cleaned, or replaced where it needs to be; clean diesel goes in; and your car is tested. Before leaving, our technicians fire it up and make sure that it's running correctly. Using pumps fine on a working forecourt and quiet enough for use outside a house at night, most jobs in which the motor hasn't run take roughly half an hour once our technicians are there. The insurer will ask for an engineer's report and your VAT invoice, and you get both at the end. Payment is on the day, with no money upfront. It's worth looking at your insurance while we travel to you: misfuelling cover comes with many policies. ## About Colthrop itself Colthrop is a suburban area in Berkshire, situated on the riverside at an elevation of 73 metres, with detached housing being the predominant type of accommodation. Colthrop lies near the town of Thatcham and other nearby places such as Mount Pleasant and Upper Bucklebury. Colthrop is located approximately 23.6 miles from Winchester and 48.4 miles from London, making it a relatively rural suburb. Colthrop has a population of around 2498 residents. ## AdBlue drains across Berkshire, Colthrop included As a residential suburb, Colthrop shares its vans nearby areas — Mount Pleasant, Upper Bucklebury — right across RG postcodes and the surrounding area beyond. Quickest of all: quote a RG19 4 postcode for the van. There's no need to shift your car. Anywhere it sits — beside Burdwood Community Centre, on a layby en route to Pipers Way Park, at home — that's where it gets cleared. Ring and ask instead of guessing if you're near a boundary, or somewhere hard to explain, like the back of Dunston House. ## The short version for Colthrop people Before you tip, read the cap. If AdBlue has gone in your diesel tank regardless, leave it off then phone 0333 366 0103. Petrol in Diesel clears it where it stands, anywhere in Berkshire.