--- title: St Catherines Hill: AdBlue in a Diesel Tank, Explained canonical: https://www.petrolinadieselcar.co.uk/adblue-in-diesel/st-catherines-hill-dorset/ location: St Catherines Hill county: Dorset latitude: 50.756690 longitude: -1.799980 service: AdBlue in a Diesel Tank updated: 2026-10-23 --- # AdBlue in a Diesel Tank in St Catherines Hill: How It Happens and How to Prevent It If AdBlue is already in your diesel tank, stop reading for a moment: leave your motor and your ignition off and ring 0333 366 0103. Caught before the engine runs, it is normally a drain and a thorough flush, done where the vehicle is around St Catherines Hill. Here before the event? In that case what follows explains why it comes about and how to stop it happening at all. ## AdBlue in a diesel motor: two tanks, two fillers Many current diesels on the roads round St Catherines Hill and Holdenhurst carry two liquids, not one. Diesel goes to your engine. AdBlue goes to the exhaust, where it is sprayed into the gas to clean it, and it lives in a tank of its own. Each tank has a filler of its own. Under one flap, next to each other: that's the arrangement on many vehicles. Elsewhere, AdBlue's filler is under the bonnet or in your boot instead. Diesel gets filled on every filling station visit, week in, week out. The AdBlue side is filled far less commonly, normally from a bottle, and usually by somebody who has to stop and think where it goes. The slip lives in that gap. ## How AdBlue in your diesel tank takes place around St Catherines Hill Three things tend to line up, and carelessness is seldom one of them. To start with, the warning. Low AdBlue brings a warning from the car, and letting it run dry leads to limp mode — hence a rushed top-up, maybe before work off Woodbury Close, or at The Stourvale on the way home after work. New-to-you cars are next, too. Rentals, new motors and company cars put their fillers in new places, and the hand goes for the cap used on the old one. A spouted bottle finds no obstacle at a diesel filler any more than at an AdBlue one. So the tip, once begun, keeps on. Jumpers Common or the middle of St Catherines Hill: it takes the same few seconds either way. ## Which filler is for AdBlue, and which for diesel? Look at these first, on a forecourt around St Catherines Hill or a drive over in Winkton. Seconds, no more. - Check the cap rather than going by position: AdBlue caps are commonly blue or marked "AdBlue", and diesel caps normally are not. - Look at the size: the smaller neck is, on many cars, the AdBlue one. - Look inside your fuel flap: plenty of vehicles carry a label there showing which fuel goes where. - Cannot find it beside your diesel filler? In that case check below the bonnet or in the boot — the handbook says which. - Check with the person who drove it last — before you leave, not when the light comes on — when you pick up a hire or company car from somewhere like the car park outside Christchurch. ## How to top up without AdBlue in the diesel tank A routine for the day the light comes on, wherever around Dorset that is. - Park then switch off. Not on a slope, not with the motor running, and not in a rush on the side of Hillside Drive. - Daft as it sounds, saying "AdBlue" out loud as you unscrew the cap works — after you have located the filler and read the cap. - Leave the diesel cap on. If both sit under one flap, check the diesel cap is still closed before you lift the bottle. - Using the bottle's own spout, pour slowly — and stop when it is full or the bottle is empty. - Shut the cap, and look again — making sure your diesel filler remained closed throughout. Only then, start the vehicle. Find at stage two or three that it's already gone into your diesel side? So stop just there. Never go on to stage five. ## Put AdBlue in your diesel tank in St Catherines Hill already? Do not start your engine: that is how the short order of things starts. On many diesels the ignition alone runs the fuel pump, and so do not switch the car on. Filling up with diesel won't thin it: instead, AdBlue sinks to the base of the tank, just where fuel is taken from. On a forecourt — Murco, Esso or another — the attendants will normally help roll the vehicle clear, if you ask. At home around St Catherines Hill? So the car stays where it is. Where the engine has been run by now, pull over safely and turn it off. On the M27, under 15 miles from St Catherines Hill, that means the next junction. Roughly how far did it go? Crossing St Catherines Hill is less a job than a trip of under 25 miles towards Southampton, so say. ## When we turn up around St Catherines Hill, what takes place? Our technicians come to the vehicle wherever it has stopped, whether that is outside Twynham Primary School, close to The Church of Jesus Christ of Latter-day Saints or on your own driveway. Both the work and the price rest on three replies — what liquid, which amount, and if it's run — so we ask. The quote is given over the phone, ahead of any van leaving. The system is then cleaned thoroughly, after the tank is emptied. AdBlue crystallises and is corrosive to some of the metals in a fuel system, so it does not wash out on its own — which is why the flush matters more here than with petrol. Your filter is flushed, or replaced where it needs to be; clean diesel goes in; and the car is tested. Your engine is started next and checked to be sure it runs correctly, all before our engineers go. Most jobs are done in roughly half an hour after we get there, provided the motor has not run — and the pumps our engineers use are safe on a busy forecourt and quiet after dark beside a house. Paying happens on the day, not upfront, and you receive the documents an insurer asks for: an engineer report and a VAT invoice. While we travel, have a look at your insurance documents; many include cover for misfuelling. ## About St Catherines Hill and where it is St Catherines Hill is a suburban area located on the coast of Dorset, with a relatively low elevation of 26 metres above sea level. St Catherines Hill sits near the neighbouring areas of Jumpers Common and Blackwater, and is close to the Fairmile district. St Catherines Hill is characterized by its predominantly detached housing stock, which reflects the area's residential nature. ## AdBlue drains across Dorset, St Catherines Hill included Blackwater and Fairmile are among the places around St Catherines Hill, a residential suburb, that the same teams cover, over BH postcodes. Quickest of all: give a BH23 2 postcode to the van. There's no need to move the vehicle. A driveway, a lay-by on the way to Blackwater Firs, a side street near Church of St John the Evangelist: our engineers drain the car where it is. Tricky to explain, like the back of Holdenhurst Parish Hall? Close to a border? Asking beats assuming, and so phone. ## St Catherines Hill drivers: the short version Before you pour, read the cap. AdBlue in the diesel tank regardless? Keep the car switched off then call 0333 366 0103; Petrol in Diesel drains it on the spot, throughout Dorset.