--- title: South Hampstead: AdBlue in a Diesel Tank, Explained canonical: https://www.petrolinadieselcar.co.uk/adblue-in-diesel/south-hampstead-greater-london/ location: South Hampstead county: Greater London latitude: 51.542020 longitude: -0.177470 service: AdBlue in a Diesel Tank updated: 2026-10-06 --- # AdBlue in a Diesel Tank in South Hampstead: Why It Occurs and How to Stop It Pause here a minute if your diesel tank already holds AdBlue in it: ignition off, motor off, and ring 0333 366 0103. A drain plus a thorough flush, done just where the vehicle sits around South Hampstead, is normally what it takes when found before your engine runs. Nothing happened yet? Further down, the page explains the reasons it occurs and the ways to avoid it altogether. ## AdBlue in a diesel vehicle: two tanks, two fillers Many modern diesels around Frognal, like those in South Hampstead, run on two fluids; the engine takes just your diesel. 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 comes with a filler of its own. On a lot of cars the two sit side by side under the same flap; on others the AdBlue filler is in your boot or under the bonnet. Diesel goes in at every filling station call-out, again and again. A driver who has to stop and work out where it goes usually tops up the AdBlue side, from a bottle, and far less regularly. The mistake grows in that gap between the two. ## South Hampstead: how AdBlue in the diesel tank happens It's rarely carelessness. Three things tend to line up. The warning comes first. As AdBlue runs low the vehicle tells you, and if it runs out altogether, the vehicle goes into limp mode. So the top-up is done in a hurry: on a driveway off Hilgrove Road before work, or in the car park at The Arches Wine Bar & Restaurant on the way home. Unfamiliar motors come second, as well. Hire cars, new vehicles and company vehicles place their fillers differently, and the hand goes for the cap used on the old one. Lastly, the spout goes in: a diesel filler or AdBlue filler, it goes in as readily, and after the pour begins, no part stops it. The same few seconds decide it, in the middle of South Hampstead or out in Swiss Cottage. ## How to tell the AdBlue filler from the diesel one Before you pour anything, whether on a driveway in Maitland Park or a forecourt in South Hampstead, check these. They take a couple of seconds. - Blue and lettering: an AdBlue cap is frequently blue, or says "AdBlue", where a diesel cap normally does not. Trust the cap, not its position. - Check the size: the smaller filler neck is, on plenty of vehicles, the AdBlue one. - The flap. Look inside the fuel flap for a label. Plenty of motors say there which fuel goes where. - The handbook says where it lives if your filler is not next to the diesel cap: your boot, or under the bonnet. - The person who drove the car last. On a hire or company car collected from somewhere like the car park outside the nearest station, ask before you leave, not when the light comes on. ## Topping up AdBlue without it reaching the diesel tank For the day the light appears — wherever it is across Greater London — a routine to follow. - Park and switch off. Not on a slope, not with your motor running, and not in a rush on the side of Dobson Close. - Find the AdBlue filler and read the cap. Say "AdBlue" out loud as you unscrew it. It sounds daft and it works. - The two under one flap? Then make sure the cap on the diesel side stays shut before raising the bottle. - Tip slowly, using the bottle's own spout. Stop when it is full or when the bottle is empty. - Close the cap, and look once more — confirm your diesel filler remained shut the whole time. Only then, start the car. If at step two or three you find you have already poured into the diesel side, stop there. Step five stays out. ## South Hampstead: already put AdBlue in your diesel tank? Do not start your engine: that's how the short order of things begins. Keep your ignition off as well, because on many diesels switching it on by itself runs the pump. Do not 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 sucked from. The staff at BP, Esso or any forecourt will usually help pushing the vehicle clear when asked. Your own driveway in South Hampstead is where it should stay. Already run? Stop once it is sensible, then turn off. On the M1, under 5 miles from South Hampstead, that means the next exit. Tell us about how far it went: a run towards Westminster, under 5 miles away, is a bigger job than a short hop across South Hampstead. ## Our arrival around South Hampstead, and what happens next Anywhere your car came to rest, whether outside Holy Trinity CofE Primary School, NW3, beside Gav the Champ or on your own drive, our van travels to it. What fluid was put in, the amount, and whether it ran: we ask because those answers decide the work and quote. That quote comes over the phone, ahead of any van leaving. The fuel system is then rinsed thoroughly, after that tank is drained. Much more than with petrol, it matters with AdBlue: the crystals build up, some metals are attacked, and none of that clears out unaided, no matter how long it is left. A test comes at the end: before that, clean diesel goes in, and the fuel filter is flushed or replaced if necessary. Your engine is fired up next and checked to be sure it runs correctly, all before our technicians leave. Most jobs are done in about half an hour after our technicians get there, provided the engine hasn't run — and the pumps we use are safe on a live forecourt and quiet at night outside a house. The insurer will ask for the engineer's report and the VAT invoice, and you get both at the end. Payment comes on the day, with no deposit. Plenty of insurance policies include misfuelling cover, so it's worth checking yours while we're on the way. ## About South Hampstead, for a moment South Hampstead is a suburban area in northwest London, situated near the River Thames and close to the city centre. South Hampstead sits at an elevation of 42 metres, with its residential streets and buildings characterised by a predominance of flat dwellings. South Hampstead is bordered by other notable areas, including Swiss Cottage, Belsize Park, and St Johns Wood, and is within walking distance of Westminster, which is approximately 3.6 miles away. ## AdBlue drains in South Hampstead and across Greater London Being a residential suburb, South Hampstead has the same vans as nearby areas — Belsize Park, St Johns Wood — all the way through NW postcodes and the surrounding area around them. Fastest of all: quote a NW6 4 postcode for our van. Your car stays where it is. We drain it where it is — a side street close to Odeon Swiss Cottage, a lay-by on the way to Swiss Cottage Open Space, a driveway. If you are near a border, or somewhere hard to explain like the back of Swiss Cottage Library, ring and ask instead of assuming. ## The short version for South Hampstead people Tip no AdBlue until you have read the cap. Petrol in Diesel empties it on the spot, anywhere across Greater London, if AdBlue has gone in your diesel tank all the same — so leave the car off and call 0333 366 0103.