--- title: Caddington: AdBlue in a Diesel Tank, Explained canonical: https://www.petrolinadieselcar.co.uk/adblue-in-diesel/caddington-bedfordshire/ location: Caddington county: Bedfordshire latitude: 51.866130 longitude: -0.457240 service: AdBlue in a Diesel Tank updated: 2026-10-28 --- # Why It Happens and How to Avoid It: AdBlue in a Diesel Tank in Caddington If AdBlue is already in your diesel tank, stop reading for a moment: leave the motor and your ignition off and phone 0333 366 0103. Normally, when your engine hasn't run, it's drained and fully cleaned where the car is in Caddington. If you are reading before it has happened, the rest of this page is about why it occurs and how to make sure it doesn't. ## Why does AdBlue in a diesel car need its own filler? Not one liquid but two: that is how plenty of newer diesels near Caddington and Farley Hill carry, with diesel for the engine. Kept in a tank of its own, AdBlue is fed into the exhaust stream to clean it. Separate tanks, separate fillers. On a lot of vehicles the two sit side by side under the same flap; on others the AdBlue filler is in the boot or under the bonnet. Topping up the diesel side at the petrol pump happens all the time. Seldom filled, AdBlue normally goes in from a bottle, poured by a driver who has to stop and think which cap it needs. It's in that gap that the error happens. ## How does AdBlue in the diesel tank happen around Caddington? Rarely is it carelessness: normally three things coincide. To start with, the warning. Low AdBlue brings a message from your car, and running out means limp mode — so a rushed top-up, maybe before work off Dunstable Road, perhaps outside The Chequers on the way home that evening. Then, the hand goes for the cap it would have used on the old car — since a hire car, a new car or a company car puts the fillers where your last one didn't. Third, the bottle fits: diesel filler or AdBlue filler, it goes in as readily, and once the pour starts, no part halts it. It takes seconds, whether in Woodside or bang in the heart of Caddington. ## Telling the AdBlue filler from the diesel filler Before you pour anything, whether on a driveway in Chaul End or a forecourt in Caddington, check these. They take a few seconds. - The cap. The AdBlue cap is often blue, or marked "AdBlue". Your diesel cap normally is not. Read it rather than going by where it sits. - On many vehicles, the size gives it away: AdBlue gets the smaller filler neck. - Check inside your fuel flap: plenty of motors have a label there showing which fuel goes where. - In the boot or under the bonnet: that is where the filler sits if it is not by your diesel cap, and the handbook tells you which. - Ask the person who drove it last — before you leave, not when the light comes on — if you collect a hire or company car from somewhere like the car park outside Luton. ## How to top up without AdBlue in your diesel tank Anywhere around Bedfordshire the light comes on, here is a routine for that day. - Turn off once parked — level ground, motor off, and not in a rush by Manor Road at the roadside. - Daft as it sounds, saying "AdBlue" out loud while you unscrew the cap does the trick — after you have located your filler and read the cap. - Leave your diesel cap on. If both sit under one flap, check the diesel cap is still closed before you lift the bottle. - Pour slowly, using the bottle's own spout. Stop when it's full or when the bottle is empty. - Shut the cap, and check again — making sure the diesel cap stayed closed throughout. After that, start your car. Find at step two or three that it has already gone into your diesel side? Then stop just there. Stage five is off limits. ## AdBlue in your diesel tank already, in Caddington? Then the order of things is short. Do not start the motor. Do not switch your ignition on; on plenty of diesels that alone runs the fuel pump. AdBlue does not mix with diesel — it sinks to the bottom of your tank, where your fuel is drawn from — so do not top up with diesel to thin it. Ask the attendants to help roll the vehicle away from the pump if you're at a forecourt — the Pace, the BP or anywhere else. On your own drive in Caddington? Then the car remains where it is. If the engine has already run, stop as soon as it is safe then switch off. Leave the M1 — under a mile out of Caddington — at the first exit. Tell us about how far it went: a run towards St Albans, under 10 miles away, is a bigger job than a short hop across Caddington. ## Our arrival in Caddington, and what takes place next Our van reaches the vehicle wherever it stopped — your own driveway, beside All Saints Church, or by Caddington Village School. Our technicians ask what went in, about how much, and if it has run, since the answers determine the work and the price. The price comes on the call, before any van leaves. Then the tank is drained and your system flushed thoroughly. With AdBlue that counts more than with petrol: it crystallises and is corrosive to some of the metals in a fuel system, so it does not wash out on its own. Your filter is cleaned, or replaced where it needs to be; fresh diesel goes in; and the vehicle is tested. Before we go, we start the car and check that it is running smoothly. Using pumps fine on a busy forecourt and quiet enough to use outside a house at night, most jobs where the engine has not run need roughly half an hour once our engineers arrive. You pay on the day, with nothing upfront, and get a VAT invoice and an engineer report for your insurer. Many insurance policies include misfuelling cover, and so it is worth checking yours whilst we are on the way. ## About Caddington itself Caddington is a village in Bedfordshire, situated approximately 28.5 miles north of London and 9.3 miles southwest of St Albans. Caddington sits at an elevation of around 175 metres, near the villages of Woodside, Aley Green, and Farleygreen. Caddington has a population of approximately 1569 residents, living in predominantly semi-detached housing. Caddington remains a rural community with a strong sense of local identity. ## AdBlue drains about Caddington, and Bedfordshire beyond Caddington is a rural village, and the teams that cover it also work the towns near it, Aley Green and Farleygreen among them, across the LU postcode area. Quickest of all: quote a LU1 4 postcode to our van. Your car stays where it is. Anywhere it sits — near The Heathfield Centre, on a layby heading to Caddington Village Green, at home — that is where it is emptied. Tricky to pin down, like the back of St Thomas the Apostle Catholic Church? Close to a county line? Checking beats assuming, so phone. ## In short, for Caddington motorists Pour no AdBlue until you have read the cap. If AdBlue has gone in your diesel tank all the same, leave the vehicle off then phone 0333 366 0103. Petrol in Diesel drains it where it waits, anywhere in Bedfordshire.