--- title: Explained: AdBlue in a Diesel Tank May Hill canonical: https://www.petrolinadieselcar.co.uk/adblue-in-diesel/may-hill-monmouthshire/ location: May Hill county: Monmouthshire latitude: 51.815300 longitude: -2.701550 service: AdBlue in a Diesel Tank updated: 2026-10-23 --- # How It Happens and How to Prevent It: AdBlue in a Diesel Tank in May Hill AdBlue already in the diesel tank? In that case put this page aside a moment, leave your ignition and engine off, and ring 0333 366 0103. Usually, when your motor hasn't run, it is drained and thoroughly purged where the vehicle sits in May Hill. The rest of this page explains why it happens and how to ensure it doesn't — useful if you are reading before it has happened. ## Two fillers, two tanks: AdBlue in a diesel motor Many newer diesels around Kymin, like those in May Hill, carry on two liquids; the motor takes only your diesel. AdBlue goes to your exhaust, where it is sprayed into the gas to fresh it, and it lives in a tank of its own. There's a filler on each 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. The diesel side is topped up at the petrol pump all the time. Far less regularly, the AdBlue side is filled — mostly from a bottle, by someone thinking about where it goes. The error lives in that gap. ## May Hill: how AdBlue in your diesel tank takes place Three things tend to line up, and carelessness is rarely one of them. The warning comes first. As AdBlue runs low the car tells you, and if it runs out completely, the vehicle drops into limp mode. So the top-up is done in a hurry: on a driveway off Old DIxton Road before work, or in the car park outside Mayhill Hotel on the way home. The old car's cap is where the hand goes — but a hire car, a new vehicle or a company car puts the fillers elsewhere. That's a second thing: a new car. Nothing halts the pour after it has started, because a bottle with a spout goes into a diesel filler as readily as an AdBlue one. The bottle fits. Dixton or the middle of May Hill: it is the same few seconds either way. ## Which filler is for AdBlue, and which for diesel? Before you pour anything, whether on a drive in Chippenham or a forecourt in May Hill, check these. They take a few seconds. - The cap. The AdBlue cap is often blue, or marked "AdBlue". The diesel cap usually isn't. Read it rather than going by where it sits. - The size. On plenty of vehicles the AdBlue filler neck is the smaller of the two. - Open the flap and check for a label — plenty of cars mark what goes in each filler just there. - The handbook shows where it lives when your filler is not next to the diesel cap: your boot, or under the bonnet. - Picking up a hire or company car, say at the car park at Lydney? Ask the person who drove the car last before leaving, not when the light comes on. ## Topping up AdBlue without it reaching the diesel tank Anywhere across Monmouthshire the light comes on, here is a routine for the day. - Park then switch off. Not on a slope, not with the motor running, and not in a rush on the side of Old Dixton Road. - Daft as it sounds, saying "AdBlue" aloud as you unscrew the cap does the trick — after you've located the filler and read the cap. - Leave the diesel cap on. If both sit under one flap, check your diesel cap is still closed before you lift the bottle. - Slowly does it, through the bottle's own spout, until it's full or the bottle runs out. - Only then, start the car: close the cap, check again, and make sure the diesel cap was never opened. If at stage two or three you find you have already poured into the diesel side, stop there. Never go on to stage five. ## May Hill: already put AdBlue in the diesel tank? Then the order of things is short. Don't start your motor. On many diesels the ignition alone runs the fuel pump, so don't switch it on. AdBlue doesn't mix with diesel — it sinks to the bottom of the tank, where your fuel is drawn from — so do not top up with diesel to dilute it. Ask the staff to help roll the vehicle clear of the petrol pump if you're at a forecourt — the Shell, the Applegreen or somewhere else. If you are on your own driveway in May Hill, leave the car where it sits. If the engine has already run, stop as soon as it is safe and switch off. On the M50, under 10 miles from May Hill, that means the next junction. A short hop across May Hill is a smaller job than a run towards Hereford, under 25 miles away, so tell us about how far it went. ## May Hill: what takes place when our technicians turn up We come to the vehicle wherever it has stopped, whether that's outside Redbrook Church of England Primary School, close to St Peter's Church, Dixton or on your own driveway. Both the work and the price rest on three answers — what fluid, which quantity, and if it has run — so we ask. During the call itself, you are told the price — before anything else. Then the tank is drained and the system cleaned thoroughly. Unlike petrol, AdBlue leaves crystals and eats at some fuel-system metals, and neither washes out by itself. That is why it counts more. Testing is last: before that, clean diesel goes in, and your filter is flushed or replaced if necessary. After that we start the engine and check it runs correctly before we leave. Unrun vehicles mostly mean a half-hour visit after the moment we arrive. The kit is safe on a busy filling station, and quiet enough for a residential street late at night. No money in advance; you settle up on the day. Afterwards, a VAT invoice and a report from the engineer are handed to you for the insurer. Many insurance policies include misfuelling cover, and so it is worth checking yours while we're on the way. ## About May Hill May Hill is a suburban area situated on the banks of the River Wye in Monmouthshire, Wales, with an elevation of around 18 metres. May Hill lies near the towns of Monmouth and Dixton, and is approximately 16 miles from the city of Hereford. May Hill has a population of around 806 people and is characterised by predominantly detached housing. May Hill is also relatively close to the English border, with London being around 112 miles away. ## AdBlue drains round May Hill, and Monmouthshire beyond Monmouth and Wyesham are among the towns near May Hill, a residential suburb, that the same teams cover, over NP postcodes. Quickest of all: give a NP25 3 postcode for the van. The vehicle remains put. A drive, a lay-by on the way to Garth Wood, a side street close to Monmouth Leisure Centre: we drain it where it stands. Ring and ask rather than assuming if you're near a boundary, or somewhere hard to describe, like the back of Monmouth War Memorial. ## The short version for May Hill people First, the cap; then, the tip. AdBlue in your diesel tank after all? Keep it off and call 0333 366 0103; Petrol in Diesel drains it where it stands, across Monmouthshire.