--- title: Mayfield: AdBlue in a Diesel Tank, Explained canonical: https://www.petrolinadieselcar.co.uk/adblue-in-diesel/mayfield-midlothian/ location: Mayfield county: Midlothian latitude: 55.871200 longitude: -3.043350 service: AdBlue in a Diesel Tank updated: 2026-10-28 --- # Preventing AdBlue in a Diesel Tank in Mayfield: Why It Occurs Pause reading a minute if the diesel tank already holds AdBlue in it: ignition off, engine off, and phone 0333 366 0103. A drain and a full flush, done just where your car stands in Mayfield, is normally all it needs if found before the motor runs. Here before the event? Then what follows covers why it happens and what to prevent it happening at all. ## Two fillers, two tanks: AdBlue in a diesel car No single fluid but two: that is what many newer diesels near Mayfield and Newtongrange carry, with diesel feeding your motor. AdBlue's own tank keeps it, and from there it is sent to the exhaust, where spraying cleans the fumes. There's a filler on every tank. Plenty of motors share a single flap for both, whereas others put the AdBlue filler to the boot or under the bonnet. Diesel goes in on each forecourt call-out, week in, week out. The AdBlue side is fuelled far less regularly, normally from a bottle, and normally by someone who has to stop and think where it goes. The mistake grows in that gap between them. ## AdBlue in the diesel tank in Mayfield: how it occurs Rarely is it carelessness: normally three things line up. On a drive off Saint Luke's Path before work, or in the car park at Rowan Tree Inn heading home: that's where the hurried top-up takes place. What is the reason for the rush? As AdBlue runs low the car tells you, and if it is empty, limp mode follows. Next, the hand reaches for the cap it would have used on the old vehicle — since a hire car, a new car or a company car puts the fillers where your last one did not. 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 pour once it has started. Bryans or the middle of Mayfield: it is the same few seconds in both. ## How to tell the AdBlue filler from the diesel one Check these before pouring, on a forecourt around Mayfield or a driveway over in Gowkshill. Seconds, no more. - Blue and marking: an AdBlue cap is regularly blue, or says "AdBlue", where a diesel cap usually doesn't. Trust the cap, not where it sits. - Plenty of cars fit AdBlue the smaller neck of the two. - The flap. Look inside your fuel flap for a label. Many cars say there which fuel goes where. - Can't see it beside your diesel filler? In that case look beneath the bonnet or inside the boot — the handbook will say which. - The person who drove the vehicle last. On a hire or company car collected from somewhere like the car park outside Newtongrange, ask before you leave, not when the light comes on. ## Keeping AdBlue out of the diesel tank when you top up On the day the light comes on — wherever you are across Midlothian — a simple routine to follow. - Turn off once parked — flat ground, engine off, and not rushed by Waverley Park on the verge. - Locate the AdBlue filler, read the cap, and say the name "AdBlue" aloud as unscrewing it. It sounds daft. It works. - The diesel cap remains on. When both sit under a flap, confirm it is closed before lifting the bottle. - Tip slowly, using the bottle's own spout. Stop when it is full or when the bottle is empty. - Only then, start the car: close the cap, check a second time, and make sure the diesel cap was never opened. If at step two or three you find you have already poured into your diesel side, stop there. Don't go on to stage five. ## Put AdBlue in the diesel tank around Mayfield already? Then the order of things is short. Don't start your engine. Do not switch the ignition on; on many diesels that alone runs the fuel pump. Do not top up with diesel to thin it: AdBlue doesn't mix with diesel, it sinks to the bottom of that tank, where your fuel is drawn from. At a forecourt — BP, Shell or another — the attendants will usually help push the car clear, when you ask. Your own drive around Mayfield is the place it should stay. If your motor has already run, stop as soon as it is safe then switch off. On the M8, under 15 miles from Mayfield, that means the next junction. A short hop across Mayfield is a smaller job than a run towards Edinburgh, under 10 miles away, so tell us roughly how far it went. ## Mayfield: what occurs when we turn up We come to the car wherever it has stopped, whether that's outside the local primary school, close to St Luke's and St Anne's or on your own driveway. Which fluid got in, the quantity, and whether it ran: our engineers ask since the answers set the work and quote. During the phone call itself, you are told the quote — before dispatch. Next: a drain, then a thorough flush of the entire system. More than with petrol, it matters here: crystals build up, certain metals corrode, and nothing washes away on its own, however long it is left. Your filter is flushed, or replaced where it needs to be; fresh diesel goes in; and your car is tested. After that our technicians fire it up and confirm it runs smoothly before leaving. Using pumps safe on a busy forecourt and quiet enough for use outside a house at night, most jobs in which your motor has not run take roughly half an hour once our engineers are there. Payment happens on the day, not upfront, and you are given the paperwork your insurer wants: an engineer's report and a VAT invoice. Misfuelling cover is part of plenty of insurance policies — so use the wait to look at yours. ## About Mayfield and where it is Mayfield is a village in Midlothian, situated inland at an elevation of 143 metres, approximately 8 miles from Edinburgh. Mayfield has a mix of housing types, with terraced houses being predominant, and is close to nearby places such as Bryans, Easthouses, and Monkswood. Mayfield is part of the wider Edinburgh urban area, but retains its own distinct character as a separate village. ## AdBlue drains across Midlothian, Mayfield included Throughout EH postcodes, our vans covering Mayfield — a rural village — work the surrounding locations too, Monkswood and Easthouses among them. A postcode starting EH22 5 gets our van to you fastest. Moving the car is not needed. The drain happens right there, be it a drive, a street near Mayfield Community Club, or a layby towards Mayfield Park. Tricky to explain, like the back of Mayfield Library? Close to a county line? Checking is better than guessing, so ring. ## The short version for Mayfield people Before you pour, read the cap. AdBlue in your diesel tank after all? Leave the car switched off then call 0333 366 0103; Petrol in Diesel drains it where it stands, throughout Midlothian.