--- title: Explained: AdBlue in a Diesel Tank Rockness canonical: https://www.petrolinadieselcar.co.uk/adblue-in-diesel/rockness-gloucestershire/ location: Rockness county: Gloucestershire latitude: 51.689720 longitude: -2.224730 service: AdBlue in a Diesel Tank updated: 2026-10-07 --- # Rockness: How Does AdBlue End Up in a Diesel Tank, and How Do You Prevent It? If AdBlue is already in your diesel tank, stop reading for a moment: leave your motor and the ignition off and ring 0333 366 0103. In Rockness, finding it before your motor turns normally means a drain and a full flush on the spot. If you are reading before it has happened, the rest of this page is about why it happens and how to make sure it does not. ## Why does AdBlue in a diesel motor need its own filler? No single liquid but two: that's what plenty of newer diesels around Rockness and Nailsworth run, with diesel for the motor. Kept in a tank of its own, AdBlue is sprayed into your exhaust gas 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 your boot or under the bonnet. The diesel side is fuelled at the pump all the time. The AdBlue side is filled far less frequently, normally from a bottle, and usually by a person who has to stop and think where it goes. The error lives in that gap. ## How AdBlue in the diesel tank happens around Rockness Three things tend to line up, and carelessness is rarely one of them. On a drive off Rockness Hill before work, or in the car park at Britannia Inn on the way home: that is where the rushed top-up takes place. Why the rush? As AdBlue runs low the car tells you, and once it is empty, limp mode follows. Unfamiliar vehicles come next, too. Rentals, new vehicles and company cars place their fillers differently, and the hand reaches for the cap used on the old one. A spout-topped bottle finds no resistance at a diesel filler any more than at an AdBlue one. And so the tip, once begun, keeps on. The same few seconds decide it, in the middle of Rockness or out in Millbottom. ## Which filler is for AdBlue, and which for diesel? Check these first, on a forecourt around Rockness or a driveway over in Worley. A few seconds, that's all. - Colour and lettering: an AdBlue cap is regularly blue, or says "AdBlue", where a diesel cap normally does not. Trust the cap, not where it sits. - The size. On plenty of motors the AdBlue filler neck is the smaller of the two. - The flap. Look inside the fuel flap for a label. Many cars say there which fuel goes where. - Cannot find it beside your diesel inlet? In that case check beneath the bonnet or in your boot — the owner's manual will say where. - Picking up a hire or company car, perhaps at the car park at Stroud? Check with whoever drove it last before you set off, rather than when the light goes on. ## Topping up AdBlue without it reaching your diesel tank Wherever in Gloucestershire the light comes on, this is a routine for that day. - Stop somewhere level, motor off, with time to spare — never hurried on the side of Horsley Road. - Say "AdBlue" out loud as you unscrew the cap, after you find the AdBlue filler and reading it. Daft, yes, yet it works. - The diesel cap remains on. Where both sit under a flap, make sure it's closed before lifting the bottle. - Stop when your tank fills or the bottle is empty; until then, pour gently through its built-in spout. - Close the cap and check again. Make sure the diesel cap was never opened. Only then start the car. Find at stage two or three that it's already gone into your diesel side? Then stop right there. Never go on to stage five. ## Put AdBlue in the diesel tank in Rockness already? The short order of things, beginning with not starting your motor. On many diesels the ignition alone runs the fuel pump, and so don't switch it on. Diluting it with more diesel won't work, since AdBlue settles to the base rather than mixing — and that is where the fuel is sucked from. Ask the staff to help roll your car clear of the pump if you're at a forecourt — the Shell, the BP or anywhere else. At home in Rockness? Then your car remains where it is. If your engine has already run, stop as soon as it is safe then switch off. On the M5, under 10 miles from Rockness, that means the next exit. About how far did it go? Hopping across Rockness is smaller work than a trip of under 15 miles to Gloucester, and so tell us. ## What takes place when our technicians arrive around Rockness Outside Horsley Church of England Primary School, close to Nailsworth Town Hall or on your own drive: wherever your car has stopped, our engineers come to it. Both the work and our price depend on three replies — which fluid, what quantity, and if it has run — so our technicians ask. On the phone call itself, you hear our quote — before dispatch. Next: a drain, then a thorough flush of the whole system. AdBlue crystallises and is corrosive to some of the metals in a fuel system, and so it doesn't wash out on its own — which is why the flush matters more with AdBlue than with petrol. The filter cleaned or, where it must be, replaced; clean diesel in; then a check of the car. Next our engineers fire it up and confirm it runs smoothly before we leave. Most jobs are done in about half an hour after our technicians get there, provided your motor hasn't run — and the pumps we use are fine on a busy forecourt and quiet after dark outside a house. 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 policy; plenty carry cover for misfuelling. ## About Rockness, for a moment Rockness is a suburban area situated on the riverside in Gloucestershire, with a mix of detached housing and a population of around 1313 residents. Rockness sits at an elevation of 113 metres, close to nearby places such as Millbottom, Walkleywood, and Harleywood. Rockness is located near the city of Gloucester, approximately 12 miles away, and is about 91 miles west of London. Rockness occupies a scenic spot in the South West region, with the River Severn flowing nearby. ## AdBlue drains in Rockness and across Gloucestershire Over GL postcodes, the vans covering Rockness — a residential suburb — work the nearby places too, Harleywood and Walkleywood included. A postcode starting GL6 0 gets our van to you fastest. Your car stays put. Our engineers drain it where it is — a side street close to Christ Church, a lay-by on the way to Queen Elizabeth Field, a driveway. If you're near a boundary, or somewhere hard to explain like the back of Quaker Friends Meeting House, ring and ask instead of assuming. ## The short version for Rockness people Read the cap before you pour. If AdBlue has gone in your diesel tank all the same, leave the car off then call 0333 366 0103. Petrol in Diesel empties it where it sits, anywhere around Gloucestershire.