--- title: AdBlue in a Diesel Tank Symonds Green: Explained canonical: https://www.petrolinadieselcar.co.uk/adblue-in-diesel/symonds-green-hertfordshire/ location: Symonds Green county: Hertfordshire latitude: 51.912010 longitude: -0.224280 service: AdBlue in a Diesel Tank updated: 2026-10-16 --- # Preventing AdBlue in a Diesel Tank in Symonds Green: Why It Occurs Keep the engine and ignition off then ring 0333 366 0103 first — reading can wait if AdBlue is already in the diesel tank. Usually, if the engine has not turned, it's emptied and fully cleaned where your car sits around Symonds Green. The rest of this page explains why it takes place and how to ensure it does not — handy if you're reading ahead of time. ## AdBlue in a diesel vehicle, and its separate tank Many newer diesels in Lower Titmore Green, like those in Symonds Green, run on two fluids; your engine gets only your diesel. Your exhaust, not your engine, is where AdBlue goes: sprayed into the fumes to fresh it, from its own tank. There is a filler for every tank. On a lot of cars the two sit side by side under the same flap; on others the AdBlue filler is in the boot or under the bonnet. Filling the diesel side at the pump goes on all the time. The AdBlue side is filled far less frequently, 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 takes place in Symonds Green Three things tend to come together, and carelessness is rarely one of them. To start with, the warning. Low AdBlue triggers a message from the vehicle, and letting it run out means limp mode — hence a hurried top-up, maybe before work off Blakeney Road, or at Tranquil Turtle on the way home after work. Then, your hand goes for the cap it would have used on the old vehicle — because a hire car, a new car or a company car places the fillers somewhere your last one didn't. And the bottle fits. A bottle with a spout goes into a diesel filler as easily as an AdBlue one, and so nothing stops the tip after it has started. Whether it occurs in Fishers Green or the middle of Symonds Green, it's the same few seconds. ## Which filler is for AdBlue, and which for diesel? Check these before pouring, at a forecourt around Symonds Green or a drive over in Titmore Green. A few seconds, that's all. - The cap. The AdBlue cap is commonly blue, or marked "AdBlue". The diesel cap usually is not. Read it instead of going by where it sits. - The size. On many motors the AdBlue filler neck is the smaller of the two. - Lift the filler flap and check for a label — plenty of motors mark which goes in each inlet right there. - In the boot or under the bonnet: that's where the filler is if it is not by your diesel cap, and the handbook says which. - Collecting a hire or company car, perhaps at the car park outside Stevenage? Check with whoever drove the car last before leaving, rather than once the light comes on. ## AdBlue top-ups that never reach the diesel tank When the light goes on, anywhere around Hertfordshire, use this routine. - Pull in on level, motor off, with time in hand — not hurried on the side of Yarmouth Road. - Locate the AdBlue filler, read the cap, and say the name "AdBlue" out loud as unscrewing it. It seems silly. It works. - If both sit under one flap, check the diesel cap is still closed before you lift the bottle — and leave the vehicle on. - Using the bottle's own spout, tip slowly — and stop when it is full or the bottle is empty. - Shut the cap, then check once more — confirm the diesel filler stayed shut the whole time. After that, start the car. Find at stage two or three that it's already gone into the diesel side? Then stop right there. Never go on to step five. ## AdBlue in your diesel tank already, around Symonds Green? What follows is a short order of things, beginning with no starting your motor. Leave the ignition off as well, because on many diesels switching it on alone runs the pump. Filling up with diesel won't thin it: rather than mixing, AdBlue drops to the bottom of the tank, just where the fuel is taken from. If you're at a forecourt, whether it is the Costco or the Esso, ask the staff to help roll your car away from the petrol pump. If you're on your own driveway in Symonds Green, leave it where it sits. Stop as soon as it is safe and switch off, if your motor has already run. Leave the A1(M) — under a mile out of Symonds Green — at the next exit. About how far did it go? Crossing Symonds Green is smaller a job than a trip of under 15 miles to St Albans, so say. ## What takes place when we turn up around Symonds Green We come to the car wherever it has stopped, whether that is outside Woolenwick Infant and Nursery School, near Christ the King or on your own driveway. The replies determine the work and the quote, and so we ask what went in, about how much, and whether it has run. You get that price on the phone, before anybody heads out. Emptying the tank comes next, then a thorough flush of the fuel system. With AdBlue that matters 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. A test is at the end: before that, fresh diesel is added, and your filter is cleaned or changed as needed. Before we go, our engineers fire it up and confirm that it is running smoothly. If the engine hasn't run, the majority of jobs take about half an hour once we're there, using pumps that are fine on a busy forecourt and quiet enough to use outside a house after dark. Payment is on the day, not upfront, and you are given the paperwork your insurer asks for: an engineer's report and a VAT invoice. Before we get there, have a look at your insurance documents; many include cover for misfuelling. ## About Symonds Green and where it is Symonds Green is a suburban area in Hertfordshire, situated approximately 28 miles north of London and 12 miles southwest of St Albans. Symonds Green sits at an elevation of around 106 metres, near the neighbouring areas of Fishers Green, Old Town, and Todds Green. Symonds Green is characterized by its predominantly terraced housing stock, which reflects the typical residential architecture of the region. ## AdBlue drains across Hertfordshire, Symonds Green included Symonds Green is a residential suburb, and our teams that cover it also work the places near it, Old Town and Todds Green among them, across the SG postcode area. A postcode starting SG1 2 gets the van to you fastest. Moving the car is not needed. Wherever it sits — beside Old Rail Station, in a lay-by heading to the green space at the edge of the village, at home — that is where it gets drained. Awkward to explain, like the back of Stevenage Old Town Library? Close to a county line? Checking beats assuming, so phone. ## Symonds Green people: the short version Always, the cap; then, the pour. Petrol in Diesel empties it where it stands, anywhere across Hertfordshire, if AdBlue has gone in the diesel tank anyway — so leave the car off then phone 0333 366 0103.