--- title: AdBlue in a Diesel Tank Creigiau: Explained canonical: https://www.petrolinadieselcar.co.uk/adblue-in-diesel/creigiau-cardiff/ location: Creigiau county: Cardiff latitude: 51.524880 longitude: -3.324700 service: AdBlue in a Diesel Tank updated: 2026-10-22 --- # Creigiau: How Does AdBlue End Up in a Diesel Tank, and How Do You Prevent It? Pause here for a moment when your diesel tank already has AdBlue in it: ignition off, engine off, and ring 0333 366 0103. In Creigiau, finding it before your motor runs normally means draining and a full flush where it stands. Not happened yet? Further down, the rest of the page explains the reasons it happens and the how to avoid it altogether. ## Two fillers, two tanks: AdBlue in a diesel car No single liquid but two: that is how plenty of modern diesels around Creigiau and Soar carry, with diesel feeding your motor. Your exhaust, not your engine, is where AdBlue ends up: sprayed into the fumes to fresh it, from a separate tank. Each tank has a filler of its own. Other vehicles put the AdBlue filler in the boot or under the bonnet; plenty more have both side by side behind one flap. Topping up your diesel side at the pump happens constantly. A driver who has to stop and think where it goes normally fills the AdBlue side, from a bottle, and far less frequently. That gap is where the mistake lives. ## Creigiau: how AdBlue in the diesel tank occurs Seldom is it carelessness: usually three things line up. The warning comes first. As AdBlue runs low the car tells you, and if it runs out altogether, the vehicle drops into limp mode. So the top-up is done in a hurry: on a driveway off Heol Creigiau before work, or in the car park at Creigiau Inn on the way home. Next, your hand goes for the cap it would have used on the old car — since a hire car, a new car or a company car places the fillers somewhere your last one did not. A spout-topped bottle finds no resistance at a diesel filler any more than at an AdBlue one. So the tip, after begun, carries on. Whether it takes place in Groes-faen or the middle of Creigiau, it's the same few seconds. ## The AdBlue filler and your diesel filler: telling them apart Whether a Creigiau forecourt or a drive over in Capel Llanilltern, take a few seconds over these before anything is poured in. - The cap. The AdBlue cap is commonly blue, or marked "AdBlue". Your diesel cap usually is not. Read it rather than going by where it sits. - Look at the size: the smaller filler neck is, on plenty of cars, the AdBlue one. - The flap. Look inside the fuel flap for a label. Plenty of motors say there which fuel goes where. - The handbook shows where it is if your filler is not next to the diesel cap: the boot, or under the bonnet. - 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 at Pontyclun. ## Keeping AdBlue out of your diesel tank when you top up Wherever across Cardiff the light comes on, this is a routine for that day. - Not in a rush on the side of Cardiff Road, not on a slope, not with the engine running: park and switch off properly. - Say "AdBlue" out loud as you unscrew the cap, after finding the AdBlue filler and reading it. Silly, perhaps, but it does the trick. - Both behind a single flap? So make sure the lid on the diesel filler is still closed ahead of lifting the bottle. - Finish when the tank is topped up or the bottle runs dry; before that, pour gently using the built-in spout. - Close the cap and check again. Make sure your diesel cap was never opened. Only then start the vehicle. Find at stage two or three that it has already gone into the diesel side? Then stop just there. Leave out step five entirely. ## Already put AdBlue in the diesel tank around Creigiau? Do not start your motor: that's where the short order of things starts. Don't switch the ignition on; on plenty of diesels that alone runs the fuel pump. AdBlue doesn't mix with diesel — it sinks to the bottom of that tank, where the fuel is pulled from — so do not top up with diesel to dilute it. The attendants at BP, Texaco or any forecourt will usually help pushing your car away when you ask. If you're on your own driveway in Creigiau, leave the vehicle where it stands. Already run? Pull over once it is safe, then turn off. Creigiau sits under 3 miles from the M4; there, take the first junction. About how far did it go? Crossing Creigiau is smaller a job than a trip of under 10 miles towards Cardiff, and so tell us. ## When our technicians get there around Creigiau, what occurs? Our engineers come to the car wherever it has stopped, whether that is outside the local primary school, near Saint Elteyrn's Church or on your own driveway. Both the work and our quote rest on three answers — which liquid, which quantity, and if it has run — so we ask. You hear that price on the phone, before anyone heads out. Draining the tank comes next, followed by a full flush of your system. Unlike petrol, AdBlue leaves crystals and attacks some fuel-system metals, and neither clears out unaided. Hence it counts more. Your filter is flushed, or replaced where it needs to be; fresh diesel goes in; and your car is tested. The motor is started next and tested to confirm it runs smoothly, all before our technicians go. If your engine hasn't 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 after dark. Nothing upfront; you settle up that day. Afterwards, a VAT invoice and the report from the engineer are handed to you for your insurer. It's worth looking at your insurance while we travel to you: misfuelling cover is included with many policies. ## About Creigiau itself Creigiau is a village situated on the banks of a river in Cardiff, with a relatively low elevation of 70 metres. Creigiau lies approximately 7 miles northwest of Cardiff city centre, within commuting distance. Creigiau is characterised by its predominantly detached housing stock, reflecting its suburban edge location. Creigiau is close to nearby villages such as Groes-faen and Rhiwsaeson. ## Creigiau and Cardiff: AdBlue drains across the area Creigiau is a village, and our vans that cover it also work the towns around it, Rhiwsaeson and Pen-y-garn among them, across the CF postcode area. Our van reaches you fastest with a postcode starting CF15 9. There's no need to shift the car. Wherever it stands — beside St. Catwg's, on a lay-by heading to Craig y Parc, at home — that is where it gets cleared. Awkward to explain, like the back of Arthur Llewellyn Jenkins? Close to a border? Checking is better than assuming, and so ring. ## The short version for Creigiau people Before you tip, read the cap. AdBlue in your diesel tank regardless? Keep it off then call 0333 366 0103; Petrol in Diesel drains it where it stands, across Cardiff.