How It Happens and How to Prevent It: AdBlue in a Diesel Tank in Erdington

Two fillers, two tanks: AdBlue in a diesel vehicle

Diesel feeds your motor — yet plenty of newer diesels driven round Erdington and Gravelly Hill hold a second fluid too. Stored in a tank of its own, AdBlue is fed into your exhaust gas and cleans it.

Each tank has its own filler. Many of vehicles have a single flap for both, while others put the AdBlue filler to your boot or under the bonnet. The diesel side is topped up at the pump all the time. A driver who has to stop and think where it goes usually tops up the AdBlue side, from a bottle, and much less commonly. It's in that gap that the slip lives.

How to tell the AdBlue filler from the diesel one

A couple of seconds is all these take — so check them before you tip anything, on a drive in Short Heath or a forecourt around Erdington.

• Blue and lettering: an AdBlue cap is regularly blue, or says "AdBlue", where a diesel cap usually doesn't. Go by the cap, not where it sits.
• Many vehicles give AdBlue the smaller filler of the two.
• The flap. Look inside the fuel flap for a label. Plenty of cars say there which fuel goes where.
• The handbook says which it lives when the filler is not next to the diesel cap: your boot, or under the bonnet.
• Collecting a hire or company car, perhaps at the car park at the nearest station? Check with whoever drove it last before leaving, rather than when the light comes on.

When our engineers arrive in Erdington, what happens?

Our van comes to the car anywhere it stopped — your own driveway, near Erdington United Reformed Church, or by Abbey Catholic Primary School. The replies settle this work and the price, so our engineers ask what went in, roughly how much, and whether it's run. You hear that price by phone, before anybody heads out.

Emptying your tank comes next, followed by a full flush of your system. Not like petrol, AdBlue forms crystals and eats at certain fuel-system metals, and neither clears away unaided. Hence it matters more. A test comes at the end: before that, clean diesel goes in, and the filter is cleaned or replaced as needed. Before we go, our technicians fire it up and check that it's running properly.

Using pumps fine on a working forecourt and quiet enough to use outside a house at night, most jobs in which your engine hasn't run need roughly half an hour after we are there. Paying is on the day, not upfront, and you receive the documents an insurer asks for: an engineer report and a VAT invoice. While we travel, have a look at your policy; plenty carry cover for misfuelling.