--- title: AdBlue in a Diesel Tank Frognal? Read This canonical: https://www.petrolinadieselcar.co.uk/adblue-in-diesel/frognal-greater-london/ location: Frognal county: Greater London latitude: 51.553170 longitude: -0.181250 service: AdBlue in a Diesel Tank updated: 2026-10-03 --- # Why It Happens and How to Avoid It: AdBlue in a Diesel Tank in Frognal Leave your engine and ignition off and phone 0333 366 0103 first — the rest can wait if AdBlue is already in your diesel tank. Normally, when your motor has not run, it's drained and fully rinsed where the vehicle sits in Frognal. If you're reading before it has happened, the remainder of this page is about why it occurs and how to make sure it does not. ## AdBlue in a diesel car, and its separate tank Plenty of modern diesels around South Hampstead, like those in Frognal, carry on two fluids; your motor gets just your diesel. Kept in a tank of its own, AdBlue is sprayed into the exhaust stream to clean it. Different tanks, different fillers. Many of cars have a single flap for the two, whereas some put the AdBlue filler to the boot or under the bonnet. At the pump, the diesel side gets filled all the time. Far less often, the AdBlue side is topped up — mostly from a bottle, by someone working out where it goes. It's in the gap that the slip lives. ## Frognal: how AdBlue in your diesel tank takes place It's hardly ever carelessness. Three things tend to line up. The warning comes first. As AdBlue runs low the car tells you, and if it runs out completely, your vehicle drops into limp mode. So the top-up is done in a hurry: on a driveway off Frognal Close before work, or in the car park outside The Horseshoe on the way home. Then the vehicle is strange. A hire car, a new motor or a company car puts the fillers where your last one did not, and the hand hits for the cap it would have used on the old one. A spout-topped bottle finds no resistance at a diesel filler no more than at an AdBlue one. So the tip, once begun, carries on. Hampstead or the heart of Frognal: it is the same few seconds either way. ## How to tell the AdBlue filler from the diesel one A few seconds is all these take — so check them before you tip anything, on a driveway in Swiss Cottage or a forecourt in Frognal. - Where it sits can mislead; the cap doesn't. AdBlue ones are often blue or bear the word "AdBlue" — diesel caps usually do not. - Check the size: the smaller neck is, on plenty of vehicles, the AdBlue one. - Lift the flap and look for a label — many cars mark which belongs in which filler right there. - The handbook. If the filler is not by your diesel cap, it is in your boot or under the bonnet, and the handbook says which. - Whoever had it before will know. Check as you pick up a hire car or company car — from Finchley Road & Frognal's car park, perhaps — rather than once the warning appears. ## Keeping AdBlue out of your diesel tank when you top up A routine for the day the light comes on, wherever in Greater London that is. - Not in a rush on the side of Arkwright Road, not on a slope, not with your motor running: park and switch off first. - Locate the AdBlue filler, read the cap, and say the name "AdBlue" out loud while you unscrew it. It sounds daft. It works. - Leave the diesel cap on. If both sit under one flap, check the diesel cap is still closed before you lift the bottle. - Stop once that tank is topped up or the bottle is empty; before that, pour slowly using the own spout. - Close the cap and check a second time. Make sure the diesel cap was never opened. Only then start the vehicle. Discover during the second or third step that the bottle went into the diesel tank? That is where you stop. Do not go on to step five. ## Frognal: already put AdBlue in the diesel tank? Short list, then. Top of that: your motor remains off. On many diesels the ignition alone runs the fuel pump, and so don't switch the vehicle on. Don't top up with diesel to dilute it: AdBlue does not mix with diesel, it sinks to the bottom of your tank, where the fuel is drawn from. Ask the attendants to help roll your car away from the pump if you are at a forecourt — the BP, the Shell or anywhere else. If you are on your own driveway in Frognal, leave the car where it sits. Where the engine has been run by now, stop somewhere safe and switch it off. Leave the M1 — under 3 miles out of Frognal — at the first junction. Tell us about how far it went: a run towards Westminster, under 5 miles away, is a bigger job than a short hop across Frognal. ## Frognal: what takes place when we arrive Our technicians come to the car wherever it has stopped, whether that is outside Hampstead Parochial Church of England Primary School, close to Kate Greenaway or on your own driveway. The answers decide this work and the quote, and so we ask what went in, roughly how much, and whether it has run. During the phone call itself, you are told our quote — ahead of anything else. Emptying the tank comes next, then a full flush of the fuel 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 the flush counts more with AdBlue than with petrol. Testing comes last: before that, fresh diesel goes in, and the fuel filter is cleaned or replaced if necessary. The motor is started next and tested to make sure it runs smoothly, all before our engineers head off. If the motor has not run, the majority of jobs take about half an hour once we're there, using pumps that are safe on a working forecourt and quiet enough to use outside a house at night. You pay on the day, with nothing upfront, and get a VAT invoice and an engineer report for your insurer. It is worth checking your insurance as the van travels to you: misfuelling cover comes with plenty of policies. ## About Frognal Frognal is a suburban area in northwest London, situated near the riverside and close to the neighbouring districts of Hampstead and West Hampstead. Frognal sits at an elevation of around 116 metres, with many of its residents living in flat dwellings. Frognal is located approximately 3.9 miles from central London and 4.3 miles from Westminster, making it a popular choice for those who work in the city. Frognal has a population of around 13390 people, according to recent estimates. ## AdBlue drains around Frognal and across Greater London Vale of Health and West Hampstead are among the places near Frognal, a residential suburb, that the same vans cover, throughout NW postcodes. Quote a postcode that starts NW3 6, and the van gets there quickest. Moving the vehicle is not needed. Wherever it sits — beside Dennis Brain, on a lay-by en route to Camden Arts Centre, at home — that is where it is emptied. Awkward to explain, like the back of Tobias Matthay? By a border? Asking is better than assuming, and so phone. ## Frognal drivers: the short version Pour no AdBlue till you've read the cap. If AdBlue has gone in your diesel tank anyway, leave the car off and phone 0333 366 0103. Petrol in Diesel clears it where it waits, anywhere around Greater London.