--- title: AdBlue in a Diesel Tank Croydon: Explained canonical: https://www.petrolinadieselcar.co.uk/adblue-in-diesel/croydon-greater-london/ location: Croydon county: Greater London latitude: 51.373640 longitude: -0.100240 service: AdBlue in a Diesel Tank updated: 2026-10-25 --- # Croydon: How Does AdBlue End Up in a Diesel Tank, and How Do You Prevent It? Stop here for a moment if the diesel tank already holds AdBlue in it: ignition off, engine off, then ring 0333 366 0103. Caught before the motor runs, it is normally a drain and a thorough flush, done where your car is around Croydon. Reading before the event? In that case what follows explains how it comes about and what to prevent it happening at all. ## Two fillers, two tanks: AdBlue in a diesel car Diesel goes to your motor — but plenty of current diesels driven around Croydon and Selhurst hold another liquid as well. Its own tank keeps it, and from there it is sent to your exhaust, where a spray treats the gas. Each tank comes with one filler of its own. Some vehicles keep the AdBlue filler in your boot or under the bonnet; a lot of others have both together behind one flap. Filling your diesel side at the petrol pump happens constantly. The AdBlue side is fuelled far less regularly, usually from a bottle, and normally by somebody who has to stop and think where it goes. That gap is where the slip lives. ## How AdBlue in the diesel tank happens around Croydon Three things tend to line up, and carelessness is seldom one of them. Haste follows from the warning. The vehicle tells you as AdBlue runs low, and a dry tank sends the vehicle into limp mode — so the top-up gets done quickly, before work on a drive off Park Street, or on the way home in the car park outside Dog & Bull. Then, your hand goes for the cap it would have used on the old car — since a rental car, a new car or a company car places the fillers somewhere your last one did not. No part halts the pour once it has started, because a bottle with a spout goes into a diesel filler as readily as an AdBlue one. The bottle fits. The same few seconds decide it, in the middle of Croydon or out in Wandle Park. ## Which filler is for AdBlue, and which for diesel? Look at these before pouring, on a forecourt in Croydon or a driveway over in Addiscombe. A few seconds, that's all. - The cap. The AdBlue cap is frequently blue, or marked "AdBlue". The diesel cap normally isn't. Read it instead of going by where it sits. - Many vehicles give AdBlue the smaller filler of the two. - A label inside the fuel flap often says which fuel goes where, on plenty of motors. Look for it. - The handbook. If the filler isn't by your diesel cap, it's in your boot or under the bonnet, and the handbook says which. - The person who drove it last. On a hire or company car collected from somewhere like the car park outside East Croydon, ask before you leave, not when the light comes on. ## Keeping AdBlue out of the diesel tank when you top up Anywhere in Greater London the light comes on, here is a routine for that day. - Park and switch off. Not on a slope, not with your engine running, and not in a rush on the side of Bell Hill. - Find the AdBlue filler, read the cap, and speak the name "AdBlue" aloud while you unscrew it. It seems daft. 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. - Finish when that tank is topped up or the bottle runs dry; before that, pour slowly through the own spout. - Close the cap and check a second time. Make sure the diesel cap was never opened. Only then start your car. If at step two or three you find you have already poured into your diesel side, stop there. Leave out step five altogether. ## AdBlue in your diesel tank already, around Croydon? Brief list, then. Top of it: the engine remains off. On many diesels the ignition alone runs the fuel pump, and so do not switch it on. AdBlue does not mix with diesel — it sinks to the bottom of that tank, where the fuel is sucked from — so do not top up with diesel to dilute it. If you're on a forecourt, whether it is the BP or the Sainsbury's, ask the attendants to help push your car clear of the petrol pump. Leave it where it is if you're on your own drive around Croydon. When your engine has run already, stop safely then switch the vehicle off. On the M23, under 10 miles from Croydon, that means the next exit. Tell us roughly how far it went: a run towards Westminster, under 10 miles away, is a bigger job than a short hop across Croydon. ## When our technicians turn up around Croydon, what occurs? We come to your car wherever it has stopped, whether that's outside St Mary's Catholic Infant School, near The Front Room or on your own drive. Our engineers ask what went in, about how much, and whether it has run, since the answers settle the work and our quote. You get that price on the phone, before anyone sets off. Then that tank is emptied and the system cleaned thoroughly. With AdBlue that matters more than with petrol: it crystallises and is corrosive to some of the metals in a fuel system, and so it doesn't wash out on its own. A test is last: before that, fresh diesel goes in, and your filter is cleaned or changed if necessary. We do not go until it has been fired up and is running properly. Unrun cars usually mean a half-hour visit after arrival. The kit is safe on a busy filling station, and hushed enough for a residential street late at night. You pay on the day, with nothing upfront, and get a VAT invoice and an engineer report for your insurer. Before we get there, take a look at your insurance documents; plenty carry cover for misfuelling. ## About Croydon, briefly Croydon is a locality in south London, situated near the River Wandle and surrounded by areas such as Wandle Park, Broad Green, and Waddon. Croydon sits at an elevation of 61 metres, approximately 9.3 miles from central London, with Westminster being the nearest city centre. Croydon is predominantly composed of flat dwellings, housing a population of around 5809 residents. Croydon is located in a densely populated urban area, with a mix of old and new buildings. ## Croydon and Greater London: AdBlue drains across the area Being a small village, Croydon has the same vans as nearby places — Broad Green, Waddon — right through CR postcodes and the surrounding area beyond. Our van gets to you fastest with a postcode starting CR0 1. The car doesn't need to move. Wherever it sits — beside Croydon War Memorial, in a layby heading to Queen's Gardens, at home — that is where it gets cleared. If you are near a boundary, or somewhere hard to describe like the back of Croydon Clocktower, ring and ask instead of guessing. ## In short, for Croydon drivers Before you pour, read the cap. If AdBlue has gone in the diesel tank all the same, leave the vehicle off and call 0333 366 0103. Petrol in Diesel empties it where it stands, anywhere around Greater London.