Newtown: How Does AdBlue End Up in a Diesel Tank, and How Do You Avoid It?

Two fillers, two tanks: AdBlue in a diesel vehicle

Many newer diesels on the roads round Newtown and Camdentown carry two liquids, not one. Diesel goes to the engine. The exhaust, not your engine, is where AdBlue goes: dosed into the gas to fresh it, from a separate tank.

Different tanks, different fillers. Plenty of motors have a single flap for the two, whereas others move the AdBlue filler to your boot or under the bonnet. Diesel goes in at every forecourt visit, week in, week out. A driver who has to stop and work out where it goes usually tops up the AdBlue side, from a bottle, and much less often. The mistake lives in that gap.

The AdBlue filler and the diesel filler: telling them apart

Whether a Newtown forecourt or a drive over in Clayhall, spend a couple of seconds over these before any goes in.

• Position misleads; the cap does not. AdBlue ones are often blue or bear the word "AdBlue" — diesel caps usually do not.
• Many vehicles fit AdBlue the smaller filler of the two.
• The flap. Look inside your fuel flap for a label. Many cars say there which fuel goes where.
• In your boot or under the bonnet: that's where your filler sits if it is not by your diesel cap, and the handbook tells you which.
• Collecting a hire or company car, perhaps at the car park outside Portsmouth Harbour? Check with whoever drove the car last before leaving, rather than once the light comes on.

Newtown: what takes place when our technicians turn up

Anywhere the car came to rest, whether outside Haselworth Primary School, near Christ Church or on your own drive, our van travels to it. The replies determine this work and our quote, so we ask what went in, about how much, and whether it's run. Nobody sets off until you've heard our quote by phone.

The system is then cleaned thoroughly, after that tank is drained. AdBlue crystallises and is corrosive to some of the metals in a fuel system, so it does not wash out on its own — which is why that counts more here than with petrol. A test comes last: before that, fresh diesel goes in, and the filter is flushed or changed if necessary. After that we fire it up and confirm it runs smoothly before we go.

Unrun vehicles mostly need a half-hour job after arrival. The kit is safe on a live filling station, and hushed enough for a driveway after dark. You pay on the day, with nothing upfront, and get a VAT invoice and an engineer report for your insurer. Many insurance policies include misfuelling cover, and so it's worth checking yours whilst we are on the way.